Bortezomib (PS-341)

Cancer Cell Int,2005 Jun 1;5(1):18.

Preclinical evaluation of the proteasome inhibitor bortezomib in cancer therapy.[Pubmed: 15929791]

Bortezomib is a highly selective, reversible inhibitor of the 26S proteasome that is indicated for single-agent use in the treatment of patients with multiple myeloma who have received at least 2 prior therapies and are progressing on their most recent therapy.
METHODS AND RESULTS:
Clinical investigations have been completed or are under way to evaluate the safety and efficacy of bortezomib alone or in combination with chemotherapy in multiple myeloma, both at relapse and presentation, as well as in other cancer types. The antiproliferative, proapoptotic, antiangiogenic, and antitumor activities of bortezomib result from proteasome inhibition and depend on the altered degradation of a host of regulatory proteins. Exposure to bortezomib has been shown to stabilize p21, p27, and p53, as well as the proapoptotic Bid and Bax proteins, caveolin-1, and inhibitor kappaB-alpha, which prevents activation of nuclear factor kappaB-induced cell survival pathways. Bortezomib also promoted the activation of the proapoptotic c-Jun-NH2 terminal kinase, as well as the endoplasmic reticulum stress response. The anticancer effects of bortezomib as a single agent have been demonstrated in xenograft models of multiple myeloma, adult T-cell leukemia, lung, breast, prostate, pancreatic, head and neck, and colon cancer, and in melanoma. In these preclinical in vivo studies, bortezomib treatment resulted in decreased tumor growth, angiogenesis, and metastasis, as well as increased survival and tumor apoptosis. In several in vitro and/or in vivo cancer models, bortezomib has also been shown to enhance the antitumor properties of several antineoplastic treatments. Importantly, bortezomib was generally well tolerated and did not appear to produce additive toxicities when combined with other therapies in the dosing regimens used in these preclinical in vivo investigations.
CONCLUSIONS:
These findings provide a rationale for further clinical trials using bortezomib alone or in combination regimens with chemotherapy, radiation therapy, immunotherapy, or novel agents in patients with hematologic malignancies or solid tumors.

Biochemistry,1996 Apr 2;35(13):3899-908.

Kinetic characterization of the chymotryptic activity of the 20S proteasome.[Pubmed: 8672420]

In a typical kinetic run, 2.00 mL of assay buffer (20 mM HEPES, 0.5 mM EDTA, 0.035% SDS, pH 7.8) and Suc-Leu-Leu-Val-Tyr-AMC in DMSO are added to a 3 mL fluorescence cuvette, and the cuvette is placed in the jacketed cell holder of a fluorescence spectrophotometer. Reaction temperature is maintained at 37℃ by a circulating water bath. After the reaction solution has reached thermal equilibrium (5 minutes), 1 μL−10 μL of the stock enzyme solution is added to the cuvette. Reaction progress is monitored by the increase in fluorescence emission at 440 nm (λex= 380 nm) that accompanies cleavage of AMC from peptide-AMC substrates.

Cancer Res,2001 Apr 1;61(7):3071-6.

The proteasome inhibitor PS-341 inhibits growth, induces apoptosis, and overcomes drug resistance in human multiple myeloma cells.[Pubmed: 11306489]

Cell lines:Human multiple myeloma cells line U266
Concentrations:  ~10 μM
Incubation Time: 2 days
Method:
The inhibitory effect of Bortezomib on cell growth is assessed by measuring MTT dye absorbance of the cells. Cells from 48-hour cultures are pulsed with 10 μL of 5 mg/mL MTT to each well for the last 4 hour of 48-hour cultures, followed by 100 μL of isopropanol containing 0.04 N HCl. Absorbance is measured at 570 nm using a spectrophotometer.

Cancer Res,2002 Sep 1;62(17):4996-5000.

Proteasome inhibitor PS-341 inhibits human myeloma cell growth in vivo and prolongs survival in a murine model.[Pubmed: 12208752]

Animal Models: Human plasmacytoma xenografts RPMI 8226
Dosages: 1 mg/kg
Administration: i.v. twice weekly for 4 weeks, then once weekly