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Title: The proteasome inhibitor PS-341 markedly enhances sensitivity of multiple myeloma tumor cells to chemotherapeutic agents. Author: Ma MH, Yang HH, Parker K, Manyak S, Friedman JM, Altamirano C, Wu ZQ, Borad MJ, Frantzen M, Roussos E, Neeser J, Mikail A, Adams J, Sjak-Shie N, Vescio RA, Berenson JR. Journal: Clin Cancer Res; 2003 Mar; 9(3):1136-44. PubMed ID: 12631619. Abstract: Increased nuclear factor kappaB (NF-kappaB) activity is associated with increased tumor cell survival in multiple myeloma. The function of NF-kappaB is inhibited through binding to its inhibitor, IkappaB. Release of activated NF-kappaB follows proteasome-mediated degradation of IkappaB resulting from phosphorylation of the inhibitor and, finally, conjugation with ubiquitin. We report that myeloma cells have enhanced IkappaBalpha phosphorylation and increased NF-kappaB activity compared with normal hematopoietic cells. The proteasome inhibitor PS-341 blocked nuclear translocation of NF-kappaB, blocked NF-kappaB DNA binding, and demonstrated consistent antitumor activity against chemoresistant and chemosensitive myeloma cells. The sensitivity of chemoresistant myeloma cells to chemotherapeutic agents was markedly increased (100,000-1,000,000-fold) when combined with a noncytotoxic dose of PS-341 without affecting normal hematopoietic cells. Similar effects were observed using a dominant negative super-repressor for IkappaBalpha. Thus, these results suggest that inhibition of NF-kappaB with PS-341 may overcome chemoresistance and allow doses of chemotherapeutic agents to be markedly reduced with antitumor effects without significant toxicity.[Abstract] [Full Text] [Related] [New Search]