Proteasome Inhibition As a Novel Therapeutic Target in Human Cancer
http://www.100md.com
《临床肿瘤学》
the Division of Hematology, Mayo Clinic, Rochester, MN
Dana-Farber Cancer Institute, Boston, MA
ABSTRACT
UBIQUITIN-PROTEASOME PATHWAY
The first step in the ubiquitin-proteasome pathway is the addition of polyubiquitinated tails to proteins destined for destruction (Fig 1). Ubiquitin is a small protein capable of forming multimeric chains.17 C-terminal glycine residues of ubiquitin molecules attach covalently to specific lysine moieties on the protein targeted for degradation.18 The selection of proteins for degradation is determined primarily at this stage and involves three enzymes, ubiquitin-activating enzyme, ubiquitin-conjugating enzyme, and ubiquitin ligase.11 This is a highly regulated process, and specific proteins can be targeted for degradation by controlling the affinity of the ubiquitin to a given substrate.18
The second step in the catalytic process is identification of these ubiquitinated proteins by the intracellular proteasome complex. The final step is degradation of identified proteins in the central portion of the proteasome complex.
STRUCTURE OF THE PROTEASOME COMPLEX
Ubiquitin-tagged proteins are recognized by the 19S regulatory complex, where the ubiquitin tags are removed. ATPases with chaperone-like activity at the base of the 19S regulatory complex then unfold the protein substrates and feed them into the inner catalytic compartments of the 20S proteasome cylinder.17,27 The opening into the 20S catalytic chamber is small (approximately 1.3 nm), and significant unfolding of the substrate is required.25 A molecular gate (N-terminal tail of the {alpha}3-subunit) also guards the opening, but it is constitutively open when the 19S regulatory units are bound to the 20S proteasome.28 Proteins entering the inner chamber are hydrolyzed by six active proteolytic sites on the -subunits (two sites each on the 1-, 2-, and 5-subunits) into small polypeptides ranging from three to 22 amino acids in length.1,17,22 Proteins cannot enter the inner cylinder through the outer walls of the 20S proteasome because the gaps between the rings are tight.
PROTEASOME INHIBITORS
Numerous proteasome inhibitors have been developed and described.9,18,33,34 Imajoh-Ohmi et al35 showed that lactacystin, an irreversible inhibitor of the catalytic -subunit of the proteasome, induces apoptosis of human monoblastic U937 cells. Later, Shinohara et al36 showed that benzyloxycarbonyl (Z)-Leu-Leu-leucinal, a tripeptide aldehyde inhibitor of the proteasome, induces p53-dependent apoptosis in leukemic cells. Tanimoto et al,37 Drexler,30 and Orlowski et al29 also made similar observations with proteasome inhibition.
These and other studies provided proof of principle that the proteasome is a valid target for anticancer therapy; however, the available inhibitors lacked specificity.9,18 Therefore, Adams et al5 designed and developed several boronic acid–derived compounds that inhibit the proteasome pathway in a highly specific manner. Most of these boronated proteasome inhibitors were active across a 60–tumor cell line panel from the National Cancer Institute, and the potency of proteasome inhibition was correlated with growth-inhibitory effects. On the basis of its potency and cytotoxicity, bortezomib was identified as the best candidate for further clinical testing.
BORTEZOMIB: PRECLINICAL ACTIVITY
Preclinical studies show that the cytotoxic and growth inhibitory effects of bortezomib are correlated with proteasome inhibition, independent of p53 status, and non-overlapping with other chemotherapeutic agents.5 Its average 50% growth inhibition across the panel of 60 cell lines from the National Cancer Institute was 3.9 nm. Further testing found significant single-agent activity in several murine and human xenograft tumor models.3,38-43
PHASE I CLINICAL TRIALS WITH BORTEZOMIB
In another phase I trial, bortezomib was studied in 43 patients with advanced solid tumors.45 Main dose-limiting adverse effects were diarrhea and neuropathy. The dosing schedule was more similar to the one used in MM trials, with treatments given twice weekly for 2 weeks (on days 1, 4, 8, and 11) followed by 1 week of rest. The maximum-tolerated dose in this trial was 1.56 mg/m2.
RATIONALE FOR CLINICAL TRIALS WITH BORTEZOMIB IN MM
Bortezomib was then studied in a human plasmacytoma xenograft mouse model.49 Significant inhibition of growth, including some complete tumor regressions, were noted in bortezomib-treated mice. Overall survival was doubled in treated mice compared with controls, and therapy was associated with tumor cell apoptosis and decreased angiogenesis.49 These preclinical results, along with evidence of activity in phase I trials, provided the rationale for phase II clinical trials with bortezomib in MM.
CLINICAL TRIALS WITH BORTEZOMIB IN MM
One hundred ninety-three patients were assessable. Most patients (n = 178) had failed all of the known active classes of drugs for the treatment of MM, with a median number of six lines (range, two to 15 lines) of prior therapy. Of the assessable patients, 53 (27%) achieved a partial response to therapy defined by the European Group for Blood and Marrow Transplant criteria.50 In addition, 14 patients (7%) achieved a minor response to therapy. The responses included 4% of patients who achieved a CR, with negative immunofixation, and a further 6% of patients with near CRs who met criteria for CR but who had persistently positive immunofixation. The median survival time for all patients was 16 months, and the median time to progression was 7 months (as compared with a median time to progression of 3 months with last prior therapy). Responses were durable, with a median response duration of 12 months in patients who achieved a CR, partial response, or minor response to therapy. Responses were associated with improvements in hemoglobin, platelet counts, renal function, performance status, and quality-of-life measures.51 The most common adverse events were gastrointestinal side effects, cytopenias (especially thrombocytopenia), fatigue, and peripheral neuropathy. These results were especially compelling considering the heavily pretreated nature of the patients; specifically, prior stem-cell transplantation had been used in 64% of patients, and 83% had received previous thalidomide therapy. Older age (> 65 years), the presence of abnormal cytogenetics, and more than 50% plasma cell bone marrow involvement were associated with a lower response rate.7,52 In contrast, chromosome 13 deletion, prior thalidomide therapy, and prior transplantation did not effect response to bortezomib.
A separate randomized phase II trial has also been conducted in patients who failed to respond or relapsed after front-line therapy for MM.53 This trial examined the following two doses of bortezomib in 54 patients: 1.0 mg/m2 (28 patients) versus 1.3 mg/m2 (26 patients) on days 1, 4, 8, and 11 every 21 days. Responses (CR, partial response, or minor response) were seen in 33% of patients at the dose level of 1.0 mg/m2 and 50% of patients at the dose level of 1.3 mg/m2, which seems to suggest a dose-response relationship, although a formal statistical comparison was not reported by the authors.
Although both phase II trials required a maximum of eight cycles of therapy, responding patients were allowed to receive continued treatment on a third study (an extension protocol). Data from 57 patients treated in this extension study show that it is safe to give at least an additional five to six cycles of therapy, with a similar toxicity profile as in the first eight cycles.53
RECOMMENDATIONS FOR USE OF BORTEZOMIB IN MM
Patients who do not respond to induction therapy for MM often benefit from autologous stem-cell transplantation because the dose-intensity of melphalan-based conditioning overcomes drug resistance.55,56 Bortezomib may prove valuable in reducing pretransplantation tumor burden in such patients and may facilitate achievement of a CR with transplantation, a key therapeutic goal in MM. Preliminary evidence indicates that, in combination with dexamethasone, bortezomib has impressive activity as pretransplantation therapy in MM, with response rates exceeding 75%.57 However, additional clinical trials are needed, and we do not recommend such use outside the context of an approved trial.
ACTIVITY OF BORTEZOMIB IN OTHER MALIGNANCIES
MECHANISM OF ACTION OF BORTEZOMIB
NF-{kappa}B Inhibition
Several effects of bortezomib, including apoptosis, seem to be mediated through inhibition of NF-{kappa}B.73 The Rel/NF-{kappa}B family of proteins are inducible dimeric transcription factors that recognize and bind a common sequence motif in nuclear DNA.73-76 NF-{kappa}B, the major transcription factor in this family, is a p50/RelA heterodimer (p50/p65) present in the cytoplasm of almost all cells.75,77 NF-{kappa}B regulates cell growth and apoptosis, as well as expression of various cytokines, adhesion molecules, and their receptors.18 In the cytoplasm, NF-{kappa}B is normally bound to its inhibitor, I-{kappa}B.76 When cells are stimulated (by cytokines, stress, or chemotherapy), signaling cascades are triggered that lead to activation of I-{kappa}B kinase, a heterodimeric protein kinase that catalyzes I-{kappa}B phosphorylation (Fig 3). I-{kappa}B kinase phosphorylates two serine residues in the amino-terminal regulatory domain of I-{kappa}B.78 The phosphorylated sites on I-{kappa}B are then recognized by E3RS(I-{kappa}B/-TrCP), an SCF-type E3 ubiquitin ligase, leading to ubiquitination.74 I-{kappa}B is then degraded by the proteasome pathway, releasing free active NF-{kappa}B. When activated (ie, released from I-{kappa}B inhibition), NF-{kappa}B translocates to the nucleus and binds to promoter regions of several target genes, thereby triggering their transcription. This leads to increased expression of various cytokines and chemokines, adhesion molecules, and cyclin D that promote cell growth and survival.73
Proteasome inhibitors inhibit NF-{kappa}B activity in cells by blocking the degradation of I-{kappa}B.73,79,80 Inhibition of NF-{kappa}B transcriptional activity plays a beneficial role in cancer by downregulating the expression of various growth, survival, and angiogenic factors. It leads to decreased levels of the proapoptotic proteins Bcl-2 and A1/Bfl-1, triggering cytochrome C release, caspase-9 activation, and apoptosis.47 Given the known role of NF-{kappa}B in MM, NF-{kappa}B inhibition is likely one of the main mechanisms by which bortezomib induces apoptosis and overcomes drug resistance.73
NF-{kappa}B is also important for the expression of cellular adhesion molecules. In MM, NF-{kappa}B activation leads to increased expression of adhesion molecules, such as ICAM-1 and VCAM-1, by plasma cells. Binding of MM cells to stroma, in turn, causes NF-{kappa}B–mediated upregulation of IL-6 secretion by the stromal cells, conferring resistance to apoptosis and chemotherapy.81-84 Bortezomib inhibits the adhesion of MM cells to stroma, an effect partly explained by its inhibition of NF-{kappa}B.46
NF-{kappa}B activation promotes the expression of various cytokines that mediate angiogenesis and growth.85 In mouse models of MM, bortezomib therapy inhibits angiogenesis, an effect that may also be related to NF-{kappa}B inhibition.49 Finally, bortezomib blocks NF-{kappa}B–dependent induction of growth factors, such as IL-6, by stromal cells.46
Although, as discussed earlier, NF-{kappa}B inhibition may be a major mechanism of action, bortezomib likely also has other effects that contribute to its antitumor activity, especially in MM. PS-1145, a specific inhibitor of I-{kappa}B kinase, causes only a 20% to 50% inhibition in proliferation of MM cells at more than 12.5 μmol/L compared with complete inhibition with bortezomib at ≤ 0.1 μmol/L concentrations.73 Furthermore, unlike PS-1145, bortezomib also induces apoptosis of MM cells.
Upregulation of Proapoptotic Pathways
Studies using microarray technology (Affymetrix U95Av2 chips; Affymetrix, Santa Clara, CA) in MM cells treated with bortezomib show upregulation of heat shock proteins and proapoptotic genes; growth and antiapoptotic genes are suppressed.47
Bortezomib activates the c-Jun N-terminal kinase (JNK) leading to Fas upregulation and caspase-8 and caspase-3 activation.47 This caspase-8–mediated apoptotic pathway is independent of the caspase-9–mediated pathway described earlier in relation to NF-{kappa}B inhibition. JNK activation seems to be an important pathway for bortezomib-induced MM cell apoptosis, and blockage of JNK by a specific inhibitor (SP600125) can inhibit this effect by inhibiting caspase-3 activation. Induction of caspase-3 leads to MDM2 degradation and p53 (ser 15) phosphorylation, thereby increasing p53 activity and apoptosis. Bortezomib also induces FasL expression, probably because of increased c-myc expression that occurs as a result of proteasome inhibition.47
Other Effects
Bortezomib downregulates expression of insulin-like growth factor-1 and insulin-like growth factor-1 receptor.47 It also inhibits IL-6–induced Ras/Raf/mitogen-activated protein kinase pathway activation, leading to inhibition of growth in MM cell lines and primary MM cells.73 However, bortezomib had no effect on IL-6–induced signaling through the JAK/STAT3 pathway.
Bortezomib also induces cytoprotective responses, such as upregulation of heat-shock proteins (eg, hsp90), and thus, inhibitors to these cytoprotective proteins can increase sensitivity or overcome resistance to bortezomib.47 Despite the data discussed earlier, the specific effects of proteasome inhibition in malignancy and the precise mechanism of action of bortezomib remain unclear and are subject to further investigation.
BORTEZOMIB: PHARMACOKINETICS AND PHARMACODYNAMICS
Because of the rapid clearing of the drug from blood, a bioassay to estimate degree of proteasome inhibition was developed to assist with phase I and II clinical trials. Primate studies have identified that the target level of proteasome inhibition should not exceed 80%. With the recommended dosing, approximately 60% proteasome inhibition is achieved. The degree of proteasome inhibition is dose dependent and does not seem to be affected significantly by patient characteristics.1 Thus, monitoring of proteasome inhibition is not needed for routine clinical practice. There are no good data on drug interactions or pharmacokinetics in children.
BORTEZOMIB: ADVERSE EFFECTS AND DOSE
There are usually no infusion-related side effects, and routine premedication is not necessary. Prophylactic antiemetics are recommended if patients experience nausea or vomiting with therapy, and administration of normal saline to ensure adequate hydration may be helpful. Fever occurs in approximately 20% of patients and is typically low grade but occasionally can reach 39°C or higher. It usually occurs in the first cycle of therapy, approximately 12 hours after drug administration, and lasts 24 to 26 hours. Cytopenias (primarily leukopenia and thrombocytopenia) are common and are managed with supportive measures. Thrombocytopenia can be of grade 3 or higher in approximately 30% of patients and may necessitate dose reduction or transfusion. In most cases, it is transient and predictable (occurring usually after day 10), with recovery by day 1 of the next cycle. In some patients, the proportion of decrease in platelet count may be constant, leading to smaller absolute decrements as the platelet count drops with therapy.
Peripheral neuropathy occurs in approximately 35% of patients and is more frequent in patients who have received prior neurotoxic therapy and in patients with pre-existing neuropathy.7,87 Neuropathy is mostly sensory and can be of grade 3 severity in approximately 10% of patients. Symptoms of neuropathy can be minimized by dose adjustments and are usually reversible with discontinuation of bortezomib. Postural hypotension (possibly dose dependent) occurs in approximately 10% of patients and is associated with dehydration, concomitant antihypertensive therapy, or autonomic dysfunction. IV saline at the time of bortezomib administration may be helpful for dehydration. The consequences of postural hypotension may be serious in patients with pre-existing low cardiac output states.
There are no pharmacokinetic data on patients with renal or hepatic impairment.86 Patients with significant renal impairment (creatinine clearance, 10 to 30 mL/min) were included in MM trials, and it does not seem that efficacy, toxicity, or degree of proteasome inhibition is affected by renal failure.88 However, bortezomib is metabolized by hepatic cytochrome p450 enzymes, and caution is recommended when using the drug in patients with liver disease.
The usual dose of bortezomib for the treatment of relapsed, refractory MM is 1.3 mg/m2 given twice weekly on days 1, 4, 8, and 11 every 21 days.7 Patients with adverse events at the standard dose of bortezomib can be dose reduced to 1 mg/m2 and 0.7 mg/m2.86
COMBINATION OF BORTEZOMIB WITH OTHER CHEMOTHERAPEUTIC AGENTS
When bortezomib is combined with melphalan in MM, initial reports have suggested promising activity, but the dose of both drugs needs to be lowered.91 Preliminary results suggest that the combination of bortezomib with pegylated doxorubicin also merits additional testing.92
In solid tumors, there is strong preclinical evidence that the activity of bortezomib is significantly higher when used in combination with chemotherapeutic agents such as gemcitabine, doxorubicin, irinotecan, docetaxel, and paclitaxel.89,93 Preliminary data from phase I trials indicate that the combination of bortezomib with other chemotherapy drugs is feasible and safe.93 Phase II clinical trials of bortezomib in combination with gemcitabine, docetaxel, irinotecan, and other cytotoxic agents are ongoing.
FUTURE DIRECTIONS
The success seen with bortezomib is remarkable because it has validated the proteasome as a novel and legitimate target in the treatment of cancer. We fully hope that other more improved inhibitors of this enzymatic system will be tested in clinical trials soon.
Authors' Disclosures of Potential Conflicts of Interest
NOTES
Supported in part by grant Nos. CA85818, CA93842, CA100080, CA62242, CA50947, and CA78378 from the National Cancer Institute, Bethesda, MD. Also supported in part by the Multiple Myeloma Research Foundation (S.V.R. and K.C.A.), Goldman Philanthropic Partnerships (S.V.R.), the Leukemia and Lymphoma Society (S.V.R.), the Myeloma Research Fund (K.C.A. and T.H.), and the Doris Duke Distinguished Clinical Research Award (K.C.A.).
The authors have received research support from Millennium Pharmaceuticals. K.C.A. and P.G.R. have received payments from Millennium Pharmaceuticals for lectures and serving on its advisory board.
Authors' disclosures of potential conflicts of interest are found at the end of this article.
REFERENCES
1. Adams J: Development of the proteasome inhibitor PS-341. Oncologist 7:9-16, 2002
2. Adams J: Proteasome inhibition in cancer: Development of PS-341. Semin Oncol 28:613-619, 2001
3. Adams J: Proteasome inhibitors as new anticancer drugs. Curr Opin Oncol 14:628-634, 2002
4. Ciechanover A: The ubiquitin-proteasome proteolytic pathway. Cell 79:13-21, 1994
5. Adams J, Palombella VJ, Sausville EA, et al: Proteasome inhibitors: A novel class of potent and effective antitumor agents. Cancer Res 59:2615-2622, 1999
6. Cheson BD: Hematologic malignancies: New developments and future treatments. Semin Oncol 29:33-45, 2002
7. Richardson PG, Barlogie B, Berenson J, et al: A phase 2 study of bortezomib in relapsed, refractory myeloma. N Engl J Med 348:2609-2617, 2003
8. Anonymous: FDA approves Velcade for multiple myeloma treatment, 2003. http://www.fda.gov/bbs/topics/NEWS/2003/NEW00905.html
9. Adams J, Palombella VJ, Elliott PJ: Proteasome inhibition: A new strategy in cancer treatment. Invest New Drugs 18:109-121, 2000
10. Adams J: Preclinical and clinical evaluation of proteasome inhibitor PS-341 for the treatment of cancer. Curr Opin Chem Biol 6:493-500, 2002
11. Hershko A, Ciechanover A: The ubiquitin system. Annu Rev Biochem 67:425-479, 1998
12. Varshavsky A: The ubiquitin system. Trend Biochem Sci 22:383-387, 1997
13. Palombella VJ, Rando OJ, Goldberg AL, et al: The ubiquitin-proteasome pathway is required for processing the NF-kappa B1 precursor protein and the activation of NF-kappa B. Cell 78:773-785, 1994
14. Palombella VJ, Conner EM, Fuseler JW, et al: Role of the proteasome and NF-kappaB in streptococcal cell wall-induced polyarthritis. Proc Natl Acad Sci U S A 95:15671-15676, 1998
15. Rock KL, Gramm C, Rothstein L, et al: Inhibitors of the proteasome block the degradation of most cell proteins and the generation of peptides presented on MHC class I molecules. Cell 78:761-771, 1994
16. Spataro V, Norbury C, Harris AL: The ubiquitin-proteasome pathway in cancer. Br J Cancer 77:448-455, 1998
17. Kloetzel PM: Antigen processing by the proteasome. Nat Rev Mol Cell Biol 2:179-187, 2001
18. Almond JB, Cohen GM: The proteasome: A novel target for cancer chemotherapy. Leukemia 16:433-443, 2002
19. Craiu A, Gaczynska M, Akopian T, et al: Lactacystin and clasto-lactacystin beta-lactone modify multiple proteasome beta-subunits and inhibit intracellular protein degradation and major histocompatibility complex class I antigen presentation. J Biol Chem 272:13437-13445, 1997
20. Orlowski M: The multicatalytic proteinase complex, a major extralysosomal proteolytic system. Biochemistry 29:10289-10297, 1990
21. Coux O, Tanaka K, Goldberg AL: Structure and functions of the 20S and 26S proteasomes. Annu Rev Biochem 65:801-847, 1996
22. Lowe J, Stock D, Jap B, et al: Crystal structure of the 20S proteasome from the archaeon T. acidophilum at 3.4 A resolution. Science 268:533-539, 1995
23. Groll M, Ditzel L, Lowe J, et al: Structure of 20S proteasome from yeast at 2.4 A resolution. Nature 386:463-471, 1997
24. Stein RL, Melandri F, Dick L: Kinetic characterization of the chymotryptic activity of the 20S proteasome. Biochemistry 35:3899-3908, 1996
25. Pickart CM, VanDemark AP: Opening doors into the proteasome. Nature Struct Biol 7:999-1001, 2000
26. Seemüller E, Lupas A, Stock D, et al: Proteasome from Thermoplasma acidophilum: A threonine protease. Science 268:579-582, 1995
27. Braun BC, Glickman M, Kraft R, et al: The base of the proteasome regulatory particle exhibits chaperone-like activity. Nature Cell Biol 1:221-226, 1999
28. Groll M, Bajorek M, Kohler A, et al: A gated channel into the proteasome core particle. Nature Struct Biol 7:1062-1067, 2000
29. Orlowski RZ, Eswara JR, Lafond-Walker A, et al: Tumor growth inhibition induced in a murine model of human Burkitt's lymphoma by a proteasome inhibitor. Cancer Res 58:4342-4348, 1998
30. Drexler HC: Activation of the cell death program by inhibition of proteasome function. Proc Natl Acad Sci U S A 94:855-860, 1997
31. Delic J, Masdehors P, Omura S, et al: The proteasome inhibitor lactacystin induces apoptosis and sensitizes chemo- and radioresistant human chronic lymphocytic leukaemia lymphocytes to TNF-alpha-initiated apoptosis. Br J Cancer 77:1103-1107, 1998
32. An B, Goldfarb RH, Siman R, et al: Novel dipeptidyl proteasome inhibitors overcome Bcl-2 protective function and selectively accumulate the cyclin-dependent kinase inhibitor p27 and induce apoptosis in transformed, but not normal, human fibroblasts. Cell Death Differ 5:1062-1075, 1998
33. Traenckner EB, Wilk S, Baeuerle PA: A proteasome inhibitor prevents activation of NF-kappa B and stabilizes a newly phosphorylated form of I kappa B-alpha that is still bound to NF-kappa B. EMBO J 13:5433-5441, 1994
34. Mori S, Tanaka K, Omura S, et al: Degradation process of ligand-stimulated platelet-derived growth factor beta-receptor involves ubiquitin-proteasome proteolytic pathway. J Biol Chem 270:29447-29452, 1995
35. Imajoh-Ohmi S, Kawaguchi T, Sugiyama S, et al: Lactacystin, a specific inhibitor of the proteasome, induces apoptosis in human monoblast U937 cells. Biochem Biophys Res Commun 217:1070-1077, 1995
36. Shinohara K, Tomioka M, Nakano H, et al: Apoptosis induction resulting from proteasome inhibition. Biochem J 317:385-388, 1996
37. Tanimoto Y, Onishi Y, Hashimoto S, et al: Peptidyl aldehyde inhibitors of proteasome induce apoptosis rapidly in mouse lymphoma RVC cells. J Biochem 121:542-549, 1997
38. Cusack JC Jr, Liu R, Houston M, et al: Enhanced chemosensitivity to CPT-11 with proteasome inhibitor PS-341: Implications for systemic nuclear factor-kappaB inhibition. Cancer Res 61:3535-3540, 2001
39. Russo SM, Tepper JE, Baldwin AS Jr, et al: Enhancement of radiosensitivity by proteasome inhibition: Implications for a role of NF-kappaB. Int J Radiat Oncol Biol Phys 50:183-193, 2001
40. Shah SA, Potter MW, McDade TP, et al: 26S proteasome inhibition induces apoptosis and limits growth of human pancreatic cancer. J Cell Biochem 82:110-122, 2001
41. Teicher BA, Ara G, Herbst R, et al: The proteasome inhibitor PS-341 in cancer therapy. Clin Cancer Res 5:2638-2645, 1999
42. Frankel A, Man S, Elliott P, et al: Lack of multicellular drug resistance observed in human ovarian and prostate carcinoma treated with the proteasome inhibitor PS-341. Clin Cancer Res 6:3719-3728, 2000
43. Bold RJ, Virudachalam S, McConkey DJ: Chemosensitization of pancreatic cancer by inhibition of the 26S proteasome. J Surg Res 100:11-17, 2001
44. Orlowski RZ, Stinchcombe TE, Mitchell BS, et al: Phase I trial of the proteasome inhibitor PS-341 in patients with refractory hematologic malignancies. J Clin Oncol 20:4420-4427, 2002
45. Aghajanian C, Soignet S, Dizon DS, et al: A phase I trial of the novel proteasome inhibitor PS341 in advanced solid tumor malignancies. Clin Cancer Res 8:2505-2511, 2002
46. Hideshima T, Richardson P, Chauhan D, et al: The proteasome inhibitor PS-341 inhibits growth, induces apoptosis, and overcomes drug resistance in human multiple myeloma cells. Cancer Res 61:3071-3076, 2001
47. Mitsiades N, Mitsiades CS, Poulaki V, et al: Molecular sequelae of proteasome inhibition in human multiple myeloma cells. Proc Natl Acad Sci U S A 99:14374-14379, 2002
48. Mitsiades N, Mitsiades CS, Richardson PG, et al: The proteasome inhibitor PS-341 potentiates sensitivity of multiple myeloma cells to conventional chemotherapeutic agents: Therapeutic applications. Blood 101:2377-2380, 2003
49. LeBlanc R, Catley LP, Hideshima T, et al: Proteasome inhibitor PS-341 inhibits human myeloma cell growth in vivo and prolongs survival in a murine model. Cancer Res 62:4996-5000, 2002
50. Blade J, Samson D, Reece D, et al: Criteria for evaluating disease response and progression in patients with multiple myeloma treated by high-dose therapy and haemopoietic stem cell transplantation: Myeloma Subcommittee of the EBMT. European Group for Blood and Marrow Transplant. Br J Haematol 102:1115-1123, 1998
51. Lee S, Richardson P, Barlogie B, et al: Quality-of-life (QOL) and clinical benefit assessment in patients with relapsed and refractory multiple myeloma (MM) treated with bortezomib. Proc Am Soc Clin Oncol 22:582, 2003 (abstr 2339)
52. Richardson PGG, Barlogie B, Berenson JR, et al: Prognostic factors associated with response in patients with relapsed and refractory multiple myeloma (MM) treated with bortezomib. Proc Am Soc Clin Oncol 22:581, 2003 (abstr 2338)
53. Berenson JR, Jagannath S, Barlogie B, et al: Experience with long-term therapy using the proteasome inhibitor, bortezomib, in advanced multiple myeloma (MM). Proc Am Soc Clin Oncol 22:581, 2003 (abstr 2337)
54. Rajkumar SV, Gertz MA, Kyle RA, et al: Current therapy for multiple myeloma. Mayo Clin Proc 77:813-822, 2002
55. Blade J, Esteve J: Treatment approaches for relapsing and refractory multiple myeloma. Acta Oncol 39:843-847, 2000
56. Rajkumar SV, Fonseca R, Lacy MQ, et al: Autologous stem cell transplantation for relapsed and primary refractory myeloma. Bone Marrow Transplant 23:1267-1272, 1999
57. Jagannath S, Durie BGM, Wolf J, et al: Bortezomib (VELCADE, formerly PS-341) as first-line therapy in patients with multiple myeloma (MM). Blood 102:452a, 2003 (abstr 1650)
58. Goy AH, East K, Mesina O, et al: Report of a phase II study of proteasome inhibitor bortezomib in patients with relapsed or refractory indolent and aggressive B-cell lymphomas. Proc Am Soc Clin Oncol 22:570, 2003 (abstr 2291)
59. O'Connor OA, Wright J, Moskowitz C, et al: Phase II clinical experience with the proteasome inhibitor bortezomib (formerly PS-341) in patients with indolent lymphomas. Proc Am Soc Clin Oncol 22:566, 2003 (abstr 2277)
60. Davis NB, Taber DA, Ansari RH, et al: A phase II trial of PS-341 in patients (pts) with renal cell cancer (RCC). Proc Am Soc Clin Oncol 22:386, 2003 (abstr 1551)
61. Drucker BJ, Schwartz L, Bacik J, et al: Phase II trial of PS-341 shows response in patients with advanced renal cell carcinoma. Proc Am Soc Clin Oncol 22:386, 2003 (abstr 1550)
62. Maki RG, Kraft A, Demetri GD, et al: A phase II multicenter study of proteasome inhibitor PS-341 (LDP-341, bortezomib) for untreated recurrent or metastatic soft tissue sarcoma (STS); CTEP study 1757. Proc Am Soc Clin Oncol 22:819, 2003 (abstr 3291)
63. Stevenson J, Nho CW, Schick J, et al: Phase II clinical/pharmacodynamic trial of the proteasome inhibitor PS-341 in advanced non-small cell lung cancer. Proc Am Soc Clin Oncol 22:202, 2003 (abstr 810)
64. Cheson BD: New drug development in non-Hodgkin lymphomas. Curr Oncol Rep 3:250-259, 2001
65. Hideshima T, Chauhan D, Podar K, et al: Novel therapies targeting the myeloma cell and its bone marrow microenvironment. Semin Oncol 28:607-612, 2001
66. Anderson KC: Multiple myeloma: How far have we come Mayo Clin Proc 78:15-17, 2003
67. Anderson KC: Targeted therapy for multiple myeloma. Semin Hematol 38:286-294, 2001
68. Hideshima T, Chauhan D, Shima Y, et al: Thalidomide and its analogs overcome drug resistance of multiple myeloma cells to conventional therapy. Blood 96:2943-2950, 2000
69. Davies FE, Raje N, Hideshima T, et al: Thalidomide and immunomodulatory derivatives augment natural killer cell cytotoxicity in multiple myeloma. Blood 98:210-216, 2001
70. Rajkumar SV: Current status of thalidomide in the treatment of cancer. Oncology 15:867-874, 2001
71. Richardson PG, Schlossman RL, Weller E, et al: Immunomodulatory drug CC-5013 overcomes drug resistance and is well tolerated in patients with relapsed multiple myeloma. Blood 100:3063-3067, 2002
72. Hideshima T, Mitsiades C, Akiyama M, et al: Molecular mechanisms mediating antimyeloma activity of proteasome inhibitor PS-341. Blood 101:1530-1534, 2003
73. Hideshima T, Chauhan D, Richardson P, et al: NF-kappa B as a therapeutic target in multiple myeloma. J Biol Chem 277:16639-16647, 2002
74. Karin M, Ben-Neriah Y: Phosphorylation meets ubiquitination: The control of NF-{kappa}B activity. Annu Rev Immunol 18:621-663, 2000
75. Gilmore TD, Koedood M, Piffat KA, et al: Rel/NF-kappaB/IkappaB proteins and cancer. Oncogene 13:1367-1378, 1996
76. Karin M: How NF-kappaB is activated: The role of the IkappaB kinase (IKK) complex. Oncogene 18:6867-6874, 1999
77. Mitsiades N, Mitsiades CS, Poulaki V, et al: Biologic sequelae of nuclear factor-kappaB blockade in multiple myeloma: Therapeutic applications. Blood 99:4079-4086, 2002
78. Karin M, Delhase M: The I kappa B kinase (IKK) and NF-kappa B: Key elements of proinflammatory signalling. Semin Immunol 12:85-98, 2000
79. Gardner RC, Assinder SJ, Christie G, et al: Characterization of peptidyl boronic acid inhibitors of mammalian 20 S and 26 S proteasomes and their inhibition of proteasomes in cultured cells. Biochem J 346:447-454, 2000
80. Hideshima T, Chauhan D, Schlossman R, et al: The role of tumor necrosis factor alpha in the pathophysiology of human multiple myeloma: Therapeutic applications. Oncogene 20:4519-4527, 2001
81. Chauhan D, Uchiyama H, Akbarali Y, et al: Multiple myeloma cell adhesion-induced interleukin-6 expression in bone marrow stromal cells involves activation of NF-kappa B. Blood 87:1104-1112, 1996
82. Hazlehurst LA, Damiano JS, Buyuksal I, et al: Adhesion to fibronectin via beta1 integrins regulates p27kip1 levels and contributes to cell adhesion mediated drug resistance (CAM-DR). Oncogene 19:4319-4327, 2000
83. Hazlehurst LA, Dalton WS: Mechanisms associated with cell adhesion mediated drug resistance (CAM- DR) in hematopoietic malignancies. Cancer Metastasis Rev 20:43-50, 2001
84. Dalton WS, Bergsagel PL, Kuehl WM, et al: Multiple myeloma, in Schechter GP, Broudy VB, Williams ME (eds): Hematology 2001. Washington, DC, American Society of Hematology, 2001, pp 157-177
85. Sunwoo JB, Chen Z, Dong G, et al: Novel proteasome inhibitor PS-341 inhibits activation of nuclear factor-kappa B, cell survival, tumor growth, and angiogenesis in squamous cell carcinoma. Clin Cancer Res 7:1419-1428, 2001
86. Millennium Pharmaceuticals: VELCADE (bortezomib) for Injection: Prescribing Information. Cambridge, MA, Millennium Pharmaceuticals, Inc, 2003
87. Richardson PG, Briemberg H, Jagannath S, et al: Peripheral neuropathy following bortezomib (VELCADE, formerly PS-341) therapy in patients with advanced multiple myeloma (MM): Characterization and reversibility. Blood 102:149a, 2003 (abstr 512)
88. Jagannath S, Barlogie B, Berenson J, et al: Limited experience from 2 phase 2 trials suggests bortezomib can be given safely in multiple myeloma (MM) patients (pts) with severe renal impairment with comparable responses and toxicities. Blood 102:236a, 2003 (abstr 828)
89. Cusack JC: Rationale for the treatment of solid tumors with the proteasome inhibitor bortezomib. Cancer Treat Rev 29:21-31, 2003
90. Jagannath S, Richardson P, Barlogie B, et al: Phase II trials of bortezomib in combination with dexamethasone in multiple myeloma (MM): Assessment of additional benefits to combination in patients with sub-optimal responses to bortezomib alone. Proc Am Soc Clin Oncol 22:582, 2003 (abstr 2341)
91. Yang HH, Vescio RA, Adams J, et al: A phase I/II study of combination treatment with bortezomib and melphalan (Vc+M) in patients with relapsed or refractory multiple myeloma (MM). Proc Am Soc Clin Oncol 22:582, 2003 (abstr 2340)
92. Orlowski RZ, Voorhees PM, Garcia R, et al: Phase I study of the proteasome inhibitor bortezomib and pegylated liposomal doxorubicin in patients with refractory hematologic malignancies. Proc Am Soc Clin Oncol 22:200, 2003 (abstr 801)
93. Lenz HJ: Clinical update: Proteasome inhibitors in solid tumors. Cancer Treat Rev 29:41-48, 2003(S. Vincent Rajkumar, Paul)
Dana-Farber Cancer Institute, Boston, MA
ABSTRACT
UBIQUITIN-PROTEASOME PATHWAY
The first step in the ubiquitin-proteasome pathway is the addition of polyubiquitinated tails to proteins destined for destruction (Fig 1). Ubiquitin is a small protein capable of forming multimeric chains.17 C-terminal glycine residues of ubiquitin molecules attach covalently to specific lysine moieties on the protein targeted for degradation.18 The selection of proteins for degradation is determined primarily at this stage and involves three enzymes, ubiquitin-activating enzyme, ubiquitin-conjugating enzyme, and ubiquitin ligase.11 This is a highly regulated process, and specific proteins can be targeted for degradation by controlling the affinity of the ubiquitin to a given substrate.18
The second step in the catalytic process is identification of these ubiquitinated proteins by the intracellular proteasome complex. The final step is degradation of identified proteins in the central portion of the proteasome complex.
STRUCTURE OF THE PROTEASOME COMPLEX
Ubiquitin-tagged proteins are recognized by the 19S regulatory complex, where the ubiquitin tags are removed. ATPases with chaperone-like activity at the base of the 19S regulatory complex then unfold the protein substrates and feed them into the inner catalytic compartments of the 20S proteasome cylinder.17,27 The opening into the 20S catalytic chamber is small (approximately 1.3 nm), and significant unfolding of the substrate is required.25 A molecular gate (N-terminal tail of the {alpha}3-subunit) also guards the opening, but it is constitutively open when the 19S regulatory units are bound to the 20S proteasome.28 Proteins entering the inner chamber are hydrolyzed by six active proteolytic sites on the -subunits (two sites each on the 1-, 2-, and 5-subunits) into small polypeptides ranging from three to 22 amino acids in length.1,17,22 Proteins cannot enter the inner cylinder through the outer walls of the 20S proteasome because the gaps between the rings are tight.
PROTEASOME INHIBITORS
Numerous proteasome inhibitors have been developed and described.9,18,33,34 Imajoh-Ohmi et al35 showed that lactacystin, an irreversible inhibitor of the catalytic -subunit of the proteasome, induces apoptosis of human monoblastic U937 cells. Later, Shinohara et al36 showed that benzyloxycarbonyl (Z)-Leu-Leu-leucinal, a tripeptide aldehyde inhibitor of the proteasome, induces p53-dependent apoptosis in leukemic cells. Tanimoto et al,37 Drexler,30 and Orlowski et al29 also made similar observations with proteasome inhibition.
These and other studies provided proof of principle that the proteasome is a valid target for anticancer therapy; however, the available inhibitors lacked specificity.9,18 Therefore, Adams et al5 designed and developed several boronic acid–derived compounds that inhibit the proteasome pathway in a highly specific manner. Most of these boronated proteasome inhibitors were active across a 60–tumor cell line panel from the National Cancer Institute, and the potency of proteasome inhibition was correlated with growth-inhibitory effects. On the basis of its potency and cytotoxicity, bortezomib was identified as the best candidate for further clinical testing.
BORTEZOMIB: PRECLINICAL ACTIVITY
Preclinical studies show that the cytotoxic and growth inhibitory effects of bortezomib are correlated with proteasome inhibition, independent of p53 status, and non-overlapping with other chemotherapeutic agents.5 Its average 50% growth inhibition across the panel of 60 cell lines from the National Cancer Institute was 3.9 nm. Further testing found significant single-agent activity in several murine and human xenograft tumor models.3,38-43
PHASE I CLINICAL TRIALS WITH BORTEZOMIB
In another phase I trial, bortezomib was studied in 43 patients with advanced solid tumors.45 Main dose-limiting adverse effects were diarrhea and neuropathy. The dosing schedule was more similar to the one used in MM trials, with treatments given twice weekly for 2 weeks (on days 1, 4, 8, and 11) followed by 1 week of rest. The maximum-tolerated dose in this trial was 1.56 mg/m2.
RATIONALE FOR CLINICAL TRIALS WITH BORTEZOMIB IN MM
Bortezomib was then studied in a human plasmacytoma xenograft mouse model.49 Significant inhibition of growth, including some complete tumor regressions, were noted in bortezomib-treated mice. Overall survival was doubled in treated mice compared with controls, and therapy was associated with tumor cell apoptosis and decreased angiogenesis.49 These preclinical results, along with evidence of activity in phase I trials, provided the rationale for phase II clinical trials with bortezomib in MM.
CLINICAL TRIALS WITH BORTEZOMIB IN MM
One hundred ninety-three patients were assessable. Most patients (n = 178) had failed all of the known active classes of drugs for the treatment of MM, with a median number of six lines (range, two to 15 lines) of prior therapy. Of the assessable patients, 53 (27%) achieved a partial response to therapy defined by the European Group for Blood and Marrow Transplant criteria.50 In addition, 14 patients (7%) achieved a minor response to therapy. The responses included 4% of patients who achieved a CR, with negative immunofixation, and a further 6% of patients with near CRs who met criteria for CR but who had persistently positive immunofixation. The median survival time for all patients was 16 months, and the median time to progression was 7 months (as compared with a median time to progression of 3 months with last prior therapy). Responses were durable, with a median response duration of 12 months in patients who achieved a CR, partial response, or minor response to therapy. Responses were associated with improvements in hemoglobin, platelet counts, renal function, performance status, and quality-of-life measures.51 The most common adverse events were gastrointestinal side effects, cytopenias (especially thrombocytopenia), fatigue, and peripheral neuropathy. These results were especially compelling considering the heavily pretreated nature of the patients; specifically, prior stem-cell transplantation had been used in 64% of patients, and 83% had received previous thalidomide therapy. Older age (> 65 years), the presence of abnormal cytogenetics, and more than 50% plasma cell bone marrow involvement were associated with a lower response rate.7,52 In contrast, chromosome 13 deletion, prior thalidomide therapy, and prior transplantation did not effect response to bortezomib.
A separate randomized phase II trial has also been conducted in patients who failed to respond or relapsed after front-line therapy for MM.53 This trial examined the following two doses of bortezomib in 54 patients: 1.0 mg/m2 (28 patients) versus 1.3 mg/m2 (26 patients) on days 1, 4, 8, and 11 every 21 days. Responses (CR, partial response, or minor response) were seen in 33% of patients at the dose level of 1.0 mg/m2 and 50% of patients at the dose level of 1.3 mg/m2, which seems to suggest a dose-response relationship, although a formal statistical comparison was not reported by the authors.
Although both phase II trials required a maximum of eight cycles of therapy, responding patients were allowed to receive continued treatment on a third study (an extension protocol). Data from 57 patients treated in this extension study show that it is safe to give at least an additional five to six cycles of therapy, with a similar toxicity profile as in the first eight cycles.53
RECOMMENDATIONS FOR USE OF BORTEZOMIB IN MM
Patients who do not respond to induction therapy for MM often benefit from autologous stem-cell transplantation because the dose-intensity of melphalan-based conditioning overcomes drug resistance.55,56 Bortezomib may prove valuable in reducing pretransplantation tumor burden in such patients and may facilitate achievement of a CR with transplantation, a key therapeutic goal in MM. Preliminary evidence indicates that, in combination with dexamethasone, bortezomib has impressive activity as pretransplantation therapy in MM, with response rates exceeding 75%.57 However, additional clinical trials are needed, and we do not recommend such use outside the context of an approved trial.
ACTIVITY OF BORTEZOMIB IN OTHER MALIGNANCIES
MECHANISM OF ACTION OF BORTEZOMIB
NF-{kappa}B Inhibition
Several effects of bortezomib, including apoptosis, seem to be mediated through inhibition of NF-{kappa}B.73 The Rel/NF-{kappa}B family of proteins are inducible dimeric transcription factors that recognize and bind a common sequence motif in nuclear DNA.73-76 NF-{kappa}B, the major transcription factor in this family, is a p50/RelA heterodimer (p50/p65) present in the cytoplasm of almost all cells.75,77 NF-{kappa}B regulates cell growth and apoptosis, as well as expression of various cytokines, adhesion molecules, and their receptors.18 In the cytoplasm, NF-{kappa}B is normally bound to its inhibitor, I-{kappa}B.76 When cells are stimulated (by cytokines, stress, or chemotherapy), signaling cascades are triggered that lead to activation of I-{kappa}B kinase, a heterodimeric protein kinase that catalyzes I-{kappa}B phosphorylation (Fig 3). I-{kappa}B kinase phosphorylates two serine residues in the amino-terminal regulatory domain of I-{kappa}B.78 The phosphorylated sites on I-{kappa}B are then recognized by E3RS(I-{kappa}B/-TrCP), an SCF-type E3 ubiquitin ligase, leading to ubiquitination.74 I-{kappa}B is then degraded by the proteasome pathway, releasing free active NF-{kappa}B. When activated (ie, released from I-{kappa}B inhibition), NF-{kappa}B translocates to the nucleus and binds to promoter regions of several target genes, thereby triggering their transcription. This leads to increased expression of various cytokines and chemokines, adhesion molecules, and cyclin D that promote cell growth and survival.73
Proteasome inhibitors inhibit NF-{kappa}B activity in cells by blocking the degradation of I-{kappa}B.73,79,80 Inhibition of NF-{kappa}B transcriptional activity plays a beneficial role in cancer by downregulating the expression of various growth, survival, and angiogenic factors. It leads to decreased levels of the proapoptotic proteins Bcl-2 and A1/Bfl-1, triggering cytochrome C release, caspase-9 activation, and apoptosis.47 Given the known role of NF-{kappa}B in MM, NF-{kappa}B inhibition is likely one of the main mechanisms by which bortezomib induces apoptosis and overcomes drug resistance.73
NF-{kappa}B is also important for the expression of cellular adhesion molecules. In MM, NF-{kappa}B activation leads to increased expression of adhesion molecules, such as ICAM-1 and VCAM-1, by plasma cells. Binding of MM cells to stroma, in turn, causes NF-{kappa}B–mediated upregulation of IL-6 secretion by the stromal cells, conferring resistance to apoptosis and chemotherapy.81-84 Bortezomib inhibits the adhesion of MM cells to stroma, an effect partly explained by its inhibition of NF-{kappa}B.46
NF-{kappa}B activation promotes the expression of various cytokines that mediate angiogenesis and growth.85 In mouse models of MM, bortezomib therapy inhibits angiogenesis, an effect that may also be related to NF-{kappa}B inhibition.49 Finally, bortezomib blocks NF-{kappa}B–dependent induction of growth factors, such as IL-6, by stromal cells.46
Although, as discussed earlier, NF-{kappa}B inhibition may be a major mechanism of action, bortezomib likely also has other effects that contribute to its antitumor activity, especially in MM. PS-1145, a specific inhibitor of I-{kappa}B kinase, causes only a 20% to 50% inhibition in proliferation of MM cells at more than 12.5 μmol/L compared with complete inhibition with bortezomib at ≤ 0.1 μmol/L concentrations.73 Furthermore, unlike PS-1145, bortezomib also induces apoptosis of MM cells.
Upregulation of Proapoptotic Pathways
Studies using microarray technology (Affymetrix U95Av2 chips; Affymetrix, Santa Clara, CA) in MM cells treated with bortezomib show upregulation of heat shock proteins and proapoptotic genes; growth and antiapoptotic genes are suppressed.47
Bortezomib activates the c-Jun N-terminal kinase (JNK) leading to Fas upregulation and caspase-8 and caspase-3 activation.47 This caspase-8–mediated apoptotic pathway is independent of the caspase-9–mediated pathway described earlier in relation to NF-{kappa}B inhibition. JNK activation seems to be an important pathway for bortezomib-induced MM cell apoptosis, and blockage of JNK by a specific inhibitor (SP600125) can inhibit this effect by inhibiting caspase-3 activation. Induction of caspase-3 leads to MDM2 degradation and p53 (ser 15) phosphorylation, thereby increasing p53 activity and apoptosis. Bortezomib also induces FasL expression, probably because of increased c-myc expression that occurs as a result of proteasome inhibition.47
Other Effects
Bortezomib downregulates expression of insulin-like growth factor-1 and insulin-like growth factor-1 receptor.47 It also inhibits IL-6–induced Ras/Raf/mitogen-activated protein kinase pathway activation, leading to inhibition of growth in MM cell lines and primary MM cells.73 However, bortezomib had no effect on IL-6–induced signaling through the JAK/STAT3 pathway.
Bortezomib also induces cytoprotective responses, such as upregulation of heat-shock proteins (eg, hsp90), and thus, inhibitors to these cytoprotective proteins can increase sensitivity or overcome resistance to bortezomib.47 Despite the data discussed earlier, the specific effects of proteasome inhibition in malignancy and the precise mechanism of action of bortezomib remain unclear and are subject to further investigation.
BORTEZOMIB: PHARMACOKINETICS AND PHARMACODYNAMICS
Because of the rapid clearing of the drug from blood, a bioassay to estimate degree of proteasome inhibition was developed to assist with phase I and II clinical trials. Primate studies have identified that the target level of proteasome inhibition should not exceed 80%. With the recommended dosing, approximately 60% proteasome inhibition is achieved. The degree of proteasome inhibition is dose dependent and does not seem to be affected significantly by patient characteristics.1 Thus, monitoring of proteasome inhibition is not needed for routine clinical practice. There are no good data on drug interactions or pharmacokinetics in children.
BORTEZOMIB: ADVERSE EFFECTS AND DOSE
There are usually no infusion-related side effects, and routine premedication is not necessary. Prophylactic antiemetics are recommended if patients experience nausea or vomiting with therapy, and administration of normal saline to ensure adequate hydration may be helpful. Fever occurs in approximately 20% of patients and is typically low grade but occasionally can reach 39°C or higher. It usually occurs in the first cycle of therapy, approximately 12 hours after drug administration, and lasts 24 to 26 hours. Cytopenias (primarily leukopenia and thrombocytopenia) are common and are managed with supportive measures. Thrombocytopenia can be of grade 3 or higher in approximately 30% of patients and may necessitate dose reduction or transfusion. In most cases, it is transient and predictable (occurring usually after day 10), with recovery by day 1 of the next cycle. In some patients, the proportion of decrease in platelet count may be constant, leading to smaller absolute decrements as the platelet count drops with therapy.
Peripheral neuropathy occurs in approximately 35% of patients and is more frequent in patients who have received prior neurotoxic therapy and in patients with pre-existing neuropathy.7,87 Neuropathy is mostly sensory and can be of grade 3 severity in approximately 10% of patients. Symptoms of neuropathy can be minimized by dose adjustments and are usually reversible with discontinuation of bortezomib. Postural hypotension (possibly dose dependent) occurs in approximately 10% of patients and is associated with dehydration, concomitant antihypertensive therapy, or autonomic dysfunction. IV saline at the time of bortezomib administration may be helpful for dehydration. The consequences of postural hypotension may be serious in patients with pre-existing low cardiac output states.
There are no pharmacokinetic data on patients with renal or hepatic impairment.86 Patients with significant renal impairment (creatinine clearance, 10 to 30 mL/min) were included in MM trials, and it does not seem that efficacy, toxicity, or degree of proteasome inhibition is affected by renal failure.88 However, bortezomib is metabolized by hepatic cytochrome p450 enzymes, and caution is recommended when using the drug in patients with liver disease.
The usual dose of bortezomib for the treatment of relapsed, refractory MM is 1.3 mg/m2 given twice weekly on days 1, 4, 8, and 11 every 21 days.7 Patients with adverse events at the standard dose of bortezomib can be dose reduced to 1 mg/m2 and 0.7 mg/m2.86
COMBINATION OF BORTEZOMIB WITH OTHER CHEMOTHERAPEUTIC AGENTS
When bortezomib is combined with melphalan in MM, initial reports have suggested promising activity, but the dose of both drugs needs to be lowered.91 Preliminary results suggest that the combination of bortezomib with pegylated doxorubicin also merits additional testing.92
In solid tumors, there is strong preclinical evidence that the activity of bortezomib is significantly higher when used in combination with chemotherapeutic agents such as gemcitabine, doxorubicin, irinotecan, docetaxel, and paclitaxel.89,93 Preliminary data from phase I trials indicate that the combination of bortezomib with other chemotherapy drugs is feasible and safe.93 Phase II clinical trials of bortezomib in combination with gemcitabine, docetaxel, irinotecan, and other cytotoxic agents are ongoing.
FUTURE DIRECTIONS
The success seen with bortezomib is remarkable because it has validated the proteasome as a novel and legitimate target in the treatment of cancer. We fully hope that other more improved inhibitors of this enzymatic system will be tested in clinical trials soon.
Authors' Disclosures of Potential Conflicts of Interest
NOTES
Supported in part by grant Nos. CA85818, CA93842, CA100080, CA62242, CA50947, and CA78378 from the National Cancer Institute, Bethesda, MD. Also supported in part by the Multiple Myeloma Research Foundation (S.V.R. and K.C.A.), Goldman Philanthropic Partnerships (S.V.R.), the Leukemia and Lymphoma Society (S.V.R.), the Myeloma Research Fund (K.C.A. and T.H.), and the Doris Duke Distinguished Clinical Research Award (K.C.A.).
The authors have received research support from Millennium Pharmaceuticals. K.C.A. and P.G.R. have received payments from Millennium Pharmaceuticals for lectures and serving on its advisory board.
Authors' disclosures of potential conflicts of interest are found at the end of this article.
REFERENCES
1. Adams J: Development of the proteasome inhibitor PS-341. Oncologist 7:9-16, 2002
2. Adams J: Proteasome inhibition in cancer: Development of PS-341. Semin Oncol 28:613-619, 2001
3. Adams J: Proteasome inhibitors as new anticancer drugs. Curr Opin Oncol 14:628-634, 2002
4. Ciechanover A: The ubiquitin-proteasome proteolytic pathway. Cell 79:13-21, 1994
5. Adams J, Palombella VJ, Sausville EA, et al: Proteasome inhibitors: A novel class of potent and effective antitumor agents. Cancer Res 59:2615-2622, 1999
6. Cheson BD: Hematologic malignancies: New developments and future treatments. Semin Oncol 29:33-45, 2002
7. Richardson PG, Barlogie B, Berenson J, et al: A phase 2 study of bortezomib in relapsed, refractory myeloma. N Engl J Med 348:2609-2617, 2003
8. Anonymous: FDA approves Velcade for multiple myeloma treatment, 2003. http://www.fda.gov/bbs/topics/NEWS/2003/NEW00905.html
9. Adams J, Palombella VJ, Elliott PJ: Proteasome inhibition: A new strategy in cancer treatment. Invest New Drugs 18:109-121, 2000
10. Adams J: Preclinical and clinical evaluation of proteasome inhibitor PS-341 for the treatment of cancer. Curr Opin Chem Biol 6:493-500, 2002
11. Hershko A, Ciechanover A: The ubiquitin system. Annu Rev Biochem 67:425-479, 1998
12. Varshavsky A: The ubiquitin system. Trend Biochem Sci 22:383-387, 1997
13. Palombella VJ, Rando OJ, Goldberg AL, et al: The ubiquitin-proteasome pathway is required for processing the NF-kappa B1 precursor protein and the activation of NF-kappa B. Cell 78:773-785, 1994
14. Palombella VJ, Conner EM, Fuseler JW, et al: Role of the proteasome and NF-kappaB in streptococcal cell wall-induced polyarthritis. Proc Natl Acad Sci U S A 95:15671-15676, 1998
15. Rock KL, Gramm C, Rothstein L, et al: Inhibitors of the proteasome block the degradation of most cell proteins and the generation of peptides presented on MHC class I molecules. Cell 78:761-771, 1994
16. Spataro V, Norbury C, Harris AL: The ubiquitin-proteasome pathway in cancer. Br J Cancer 77:448-455, 1998
17. Kloetzel PM: Antigen processing by the proteasome. Nat Rev Mol Cell Biol 2:179-187, 2001
18. Almond JB, Cohen GM: The proteasome: A novel target for cancer chemotherapy. Leukemia 16:433-443, 2002
19. Craiu A, Gaczynska M, Akopian T, et al: Lactacystin and clasto-lactacystin beta-lactone modify multiple proteasome beta-subunits and inhibit intracellular protein degradation and major histocompatibility complex class I antigen presentation. J Biol Chem 272:13437-13445, 1997
20. Orlowski M: The multicatalytic proteinase complex, a major extralysosomal proteolytic system. Biochemistry 29:10289-10297, 1990
21. Coux O, Tanaka K, Goldberg AL: Structure and functions of the 20S and 26S proteasomes. Annu Rev Biochem 65:801-847, 1996
22. Lowe J, Stock D, Jap B, et al: Crystal structure of the 20S proteasome from the archaeon T. acidophilum at 3.4 A resolution. Science 268:533-539, 1995
23. Groll M, Ditzel L, Lowe J, et al: Structure of 20S proteasome from yeast at 2.4 A resolution. Nature 386:463-471, 1997
24. Stein RL, Melandri F, Dick L: Kinetic characterization of the chymotryptic activity of the 20S proteasome. Biochemistry 35:3899-3908, 1996
25. Pickart CM, VanDemark AP: Opening doors into the proteasome. Nature Struct Biol 7:999-1001, 2000
26. Seemüller E, Lupas A, Stock D, et al: Proteasome from Thermoplasma acidophilum: A threonine protease. Science 268:579-582, 1995
27. Braun BC, Glickman M, Kraft R, et al: The base of the proteasome regulatory particle exhibits chaperone-like activity. Nature Cell Biol 1:221-226, 1999
28. Groll M, Bajorek M, Kohler A, et al: A gated channel into the proteasome core particle. Nature Struct Biol 7:1062-1067, 2000
29. Orlowski RZ, Eswara JR, Lafond-Walker A, et al: Tumor growth inhibition induced in a murine model of human Burkitt's lymphoma by a proteasome inhibitor. Cancer Res 58:4342-4348, 1998
30. Drexler HC: Activation of the cell death program by inhibition of proteasome function. Proc Natl Acad Sci U S A 94:855-860, 1997
31. Delic J, Masdehors P, Omura S, et al: The proteasome inhibitor lactacystin induces apoptosis and sensitizes chemo- and radioresistant human chronic lymphocytic leukaemia lymphocytes to TNF-alpha-initiated apoptosis. Br J Cancer 77:1103-1107, 1998
32. An B, Goldfarb RH, Siman R, et al: Novel dipeptidyl proteasome inhibitors overcome Bcl-2 protective function and selectively accumulate the cyclin-dependent kinase inhibitor p27 and induce apoptosis in transformed, but not normal, human fibroblasts. Cell Death Differ 5:1062-1075, 1998
33. Traenckner EB, Wilk S, Baeuerle PA: A proteasome inhibitor prevents activation of NF-kappa B and stabilizes a newly phosphorylated form of I kappa B-alpha that is still bound to NF-kappa B. EMBO J 13:5433-5441, 1994
34. Mori S, Tanaka K, Omura S, et al: Degradation process of ligand-stimulated platelet-derived growth factor beta-receptor involves ubiquitin-proteasome proteolytic pathway. J Biol Chem 270:29447-29452, 1995
35. Imajoh-Ohmi S, Kawaguchi T, Sugiyama S, et al: Lactacystin, a specific inhibitor of the proteasome, induces apoptosis in human monoblast U937 cells. Biochem Biophys Res Commun 217:1070-1077, 1995
36. Shinohara K, Tomioka M, Nakano H, et al: Apoptosis induction resulting from proteasome inhibition. Biochem J 317:385-388, 1996
37. Tanimoto Y, Onishi Y, Hashimoto S, et al: Peptidyl aldehyde inhibitors of proteasome induce apoptosis rapidly in mouse lymphoma RVC cells. J Biochem 121:542-549, 1997
38. Cusack JC Jr, Liu R, Houston M, et al: Enhanced chemosensitivity to CPT-11 with proteasome inhibitor PS-341: Implications for systemic nuclear factor-kappaB inhibition. Cancer Res 61:3535-3540, 2001
39. Russo SM, Tepper JE, Baldwin AS Jr, et al: Enhancement of radiosensitivity by proteasome inhibition: Implications for a role of NF-kappaB. Int J Radiat Oncol Biol Phys 50:183-193, 2001
40. Shah SA, Potter MW, McDade TP, et al: 26S proteasome inhibition induces apoptosis and limits growth of human pancreatic cancer. J Cell Biochem 82:110-122, 2001
41. Teicher BA, Ara G, Herbst R, et al: The proteasome inhibitor PS-341 in cancer therapy. Clin Cancer Res 5:2638-2645, 1999
42. Frankel A, Man S, Elliott P, et al: Lack of multicellular drug resistance observed in human ovarian and prostate carcinoma treated with the proteasome inhibitor PS-341. Clin Cancer Res 6:3719-3728, 2000
43. Bold RJ, Virudachalam S, McConkey DJ: Chemosensitization of pancreatic cancer by inhibition of the 26S proteasome. J Surg Res 100:11-17, 2001
44. Orlowski RZ, Stinchcombe TE, Mitchell BS, et al: Phase I trial of the proteasome inhibitor PS-341 in patients with refractory hematologic malignancies. J Clin Oncol 20:4420-4427, 2002
45. Aghajanian C, Soignet S, Dizon DS, et al: A phase I trial of the novel proteasome inhibitor PS341 in advanced solid tumor malignancies. Clin Cancer Res 8:2505-2511, 2002
46. Hideshima T, Richardson P, Chauhan D, et al: The proteasome inhibitor PS-341 inhibits growth, induces apoptosis, and overcomes drug resistance in human multiple myeloma cells. Cancer Res 61:3071-3076, 2001
47. Mitsiades N, Mitsiades CS, Poulaki V, et al: Molecular sequelae of proteasome inhibition in human multiple myeloma cells. Proc Natl Acad Sci U S A 99:14374-14379, 2002
48. Mitsiades N, Mitsiades CS, Richardson PG, et al: The proteasome inhibitor PS-341 potentiates sensitivity of multiple myeloma cells to conventional chemotherapeutic agents: Therapeutic applications. Blood 101:2377-2380, 2003
49. LeBlanc R, Catley LP, Hideshima T, et al: Proteasome inhibitor PS-341 inhibits human myeloma cell growth in vivo and prolongs survival in a murine model. Cancer Res 62:4996-5000, 2002
50. Blade J, Samson D, Reece D, et al: Criteria for evaluating disease response and progression in patients with multiple myeloma treated by high-dose therapy and haemopoietic stem cell transplantation: Myeloma Subcommittee of the EBMT. European Group for Blood and Marrow Transplant. Br J Haematol 102:1115-1123, 1998
51. Lee S, Richardson P, Barlogie B, et al: Quality-of-life (QOL) and clinical benefit assessment in patients with relapsed and refractory multiple myeloma (MM) treated with bortezomib. Proc Am Soc Clin Oncol 22:582, 2003 (abstr 2339)
52. Richardson PGG, Barlogie B, Berenson JR, et al: Prognostic factors associated with response in patients with relapsed and refractory multiple myeloma (MM) treated with bortezomib. Proc Am Soc Clin Oncol 22:581, 2003 (abstr 2338)
53. Berenson JR, Jagannath S, Barlogie B, et al: Experience with long-term therapy using the proteasome inhibitor, bortezomib, in advanced multiple myeloma (MM). Proc Am Soc Clin Oncol 22:581, 2003 (abstr 2337)
54. Rajkumar SV, Gertz MA, Kyle RA, et al: Current therapy for multiple myeloma. Mayo Clin Proc 77:813-822, 2002
55. Blade J, Esteve J: Treatment approaches for relapsing and refractory multiple myeloma. Acta Oncol 39:843-847, 2000
56. Rajkumar SV, Fonseca R, Lacy MQ, et al: Autologous stem cell transplantation for relapsed and primary refractory myeloma. Bone Marrow Transplant 23:1267-1272, 1999
57. Jagannath S, Durie BGM, Wolf J, et al: Bortezomib (VELCADE, formerly PS-341) as first-line therapy in patients with multiple myeloma (MM). Blood 102:452a, 2003 (abstr 1650)
58. Goy AH, East K, Mesina O, et al: Report of a phase II study of proteasome inhibitor bortezomib in patients with relapsed or refractory indolent and aggressive B-cell lymphomas. Proc Am Soc Clin Oncol 22:570, 2003 (abstr 2291)
59. O'Connor OA, Wright J, Moskowitz C, et al: Phase II clinical experience with the proteasome inhibitor bortezomib (formerly PS-341) in patients with indolent lymphomas. Proc Am Soc Clin Oncol 22:566, 2003 (abstr 2277)
60. Davis NB, Taber DA, Ansari RH, et al: A phase II trial of PS-341 in patients (pts) with renal cell cancer (RCC). Proc Am Soc Clin Oncol 22:386, 2003 (abstr 1551)
61. Drucker BJ, Schwartz L, Bacik J, et al: Phase II trial of PS-341 shows response in patients with advanced renal cell carcinoma. Proc Am Soc Clin Oncol 22:386, 2003 (abstr 1550)
62. Maki RG, Kraft A, Demetri GD, et al: A phase II multicenter study of proteasome inhibitor PS-341 (LDP-341, bortezomib) for untreated recurrent or metastatic soft tissue sarcoma (STS); CTEP study 1757. Proc Am Soc Clin Oncol 22:819, 2003 (abstr 3291)
63. Stevenson J, Nho CW, Schick J, et al: Phase II clinical/pharmacodynamic trial of the proteasome inhibitor PS-341 in advanced non-small cell lung cancer. Proc Am Soc Clin Oncol 22:202, 2003 (abstr 810)
64. Cheson BD: New drug development in non-Hodgkin lymphomas. Curr Oncol Rep 3:250-259, 2001
65. Hideshima T, Chauhan D, Podar K, et al: Novel therapies targeting the myeloma cell and its bone marrow microenvironment. Semin Oncol 28:607-612, 2001
66. Anderson KC: Multiple myeloma: How far have we come Mayo Clin Proc 78:15-17, 2003
67. Anderson KC: Targeted therapy for multiple myeloma. Semin Hematol 38:286-294, 2001
68. Hideshima T, Chauhan D, Shima Y, et al: Thalidomide and its analogs overcome drug resistance of multiple myeloma cells to conventional therapy. Blood 96:2943-2950, 2000
69. Davies FE, Raje N, Hideshima T, et al: Thalidomide and immunomodulatory derivatives augment natural killer cell cytotoxicity in multiple myeloma. Blood 98:210-216, 2001
70. Rajkumar SV: Current status of thalidomide in the treatment of cancer. Oncology 15:867-874, 2001
71. Richardson PG, Schlossman RL, Weller E, et al: Immunomodulatory drug CC-5013 overcomes drug resistance and is well tolerated in patients with relapsed multiple myeloma. Blood 100:3063-3067, 2002
72. Hideshima T, Mitsiades C, Akiyama M, et al: Molecular mechanisms mediating antimyeloma activity of proteasome inhibitor PS-341. Blood 101:1530-1534, 2003
73. Hideshima T, Chauhan D, Richardson P, et al: NF-kappa B as a therapeutic target in multiple myeloma. J Biol Chem 277:16639-16647, 2002
74. Karin M, Ben-Neriah Y: Phosphorylation meets ubiquitination: The control of NF-{kappa}B activity. Annu Rev Immunol 18:621-663, 2000
75. Gilmore TD, Koedood M, Piffat KA, et al: Rel/NF-kappaB/IkappaB proteins and cancer. Oncogene 13:1367-1378, 1996
76. Karin M: How NF-kappaB is activated: The role of the IkappaB kinase (IKK) complex. Oncogene 18:6867-6874, 1999
77. Mitsiades N, Mitsiades CS, Poulaki V, et al: Biologic sequelae of nuclear factor-kappaB blockade in multiple myeloma: Therapeutic applications. Blood 99:4079-4086, 2002
78. Karin M, Delhase M: The I kappa B kinase (IKK) and NF-kappa B: Key elements of proinflammatory signalling. Semin Immunol 12:85-98, 2000
79. Gardner RC, Assinder SJ, Christie G, et al: Characterization of peptidyl boronic acid inhibitors of mammalian 20 S and 26 S proteasomes and their inhibition of proteasomes in cultured cells. Biochem J 346:447-454, 2000
80. Hideshima T, Chauhan D, Schlossman R, et al: The role of tumor necrosis factor alpha in the pathophysiology of human multiple myeloma: Therapeutic applications. Oncogene 20:4519-4527, 2001
81. Chauhan D, Uchiyama H, Akbarali Y, et al: Multiple myeloma cell adhesion-induced interleukin-6 expression in bone marrow stromal cells involves activation of NF-kappa B. Blood 87:1104-1112, 1996
82. Hazlehurst LA, Damiano JS, Buyuksal I, et al: Adhesion to fibronectin via beta1 integrins regulates p27kip1 levels and contributes to cell adhesion mediated drug resistance (CAM-DR). Oncogene 19:4319-4327, 2000
83. Hazlehurst LA, Dalton WS: Mechanisms associated with cell adhesion mediated drug resistance (CAM- DR) in hematopoietic malignancies. Cancer Metastasis Rev 20:43-50, 2001
84. Dalton WS, Bergsagel PL, Kuehl WM, et al: Multiple myeloma, in Schechter GP, Broudy VB, Williams ME (eds): Hematology 2001. Washington, DC, American Society of Hematology, 2001, pp 157-177
85. Sunwoo JB, Chen Z, Dong G, et al: Novel proteasome inhibitor PS-341 inhibits activation of nuclear factor-kappa B, cell survival, tumor growth, and angiogenesis in squamous cell carcinoma. Clin Cancer Res 7:1419-1428, 2001
86. Millennium Pharmaceuticals: VELCADE (bortezomib) for Injection: Prescribing Information. Cambridge, MA, Millennium Pharmaceuticals, Inc, 2003
87. Richardson PG, Briemberg H, Jagannath S, et al: Peripheral neuropathy following bortezomib (VELCADE, formerly PS-341) therapy in patients with advanced multiple myeloma (MM): Characterization and reversibility. Blood 102:149a, 2003 (abstr 512)
88. Jagannath S, Barlogie B, Berenson J, et al: Limited experience from 2 phase 2 trials suggests bortezomib can be given safely in multiple myeloma (MM) patients (pts) with severe renal impairment with comparable responses and toxicities. Blood 102:236a, 2003 (abstr 828)
89. Cusack JC: Rationale for the treatment of solid tumors with the proteasome inhibitor bortezomib. Cancer Treat Rev 29:21-31, 2003
90. Jagannath S, Richardson P, Barlogie B, et al: Phase II trials of bortezomib in combination with dexamethasone in multiple myeloma (MM): Assessment of additional benefits to combination in patients with sub-optimal responses to bortezomib alone. Proc Am Soc Clin Oncol 22:582, 2003 (abstr 2341)
91. Yang HH, Vescio RA, Adams J, et al: A phase I/II study of combination treatment with bortezomib and melphalan (Vc+M) in patients with relapsed or refractory multiple myeloma (MM). Proc Am Soc Clin Oncol 22:582, 2003 (abstr 2340)
92. Orlowski RZ, Voorhees PM, Garcia R, et al: Phase I study of the proteasome inhibitor bortezomib and pegylated liposomal doxorubicin in patients with refractory hematologic malignancies. Proc Am Soc Clin Oncol 22:200, 2003 (abstr 801)
93. Lenz HJ: Clinical update: Proteasome inhibitors in solid tumors. Cancer Treat Rev 29:41-48, 2003(S. Vincent Rajkumar, Paul)