Alterations in the Noxa/Mcl-1 axis determine sensitivity of small cell lung cancer to the BH3 mimetic ABT-737.
To understand the molecular basis for variable sensitivity to the BH3 mimetic drug ABT-737, the abundance of Bcl-2 family members was assayed in a panel of small cell lung cancer cell lines whose sensitivity varied over a 2-log range. Elevated Noxa and Bcl-2 levels directly correlated with sensitivity to ABT-737, whereas Mcl-1 levels were similar in all cell lines tested regardless of sensitivity. Transgenically enforced expression of Noxa but not Bcl-2 resulted in increased sensitivity to ABT-737 in multiple cell lines. This increase was especially pronounced in the H209 cell line in which expression of Noxa resulted in a proportionate decline in Mcl-1 expression. Although overexpression of Noxa enhanced sensitivity of the H526 and H82 cell lines to ABT-737, it did not result in altered Mcl-1 levels. Similarly, small interfering RNA-mediated knockdown of Noxa expression in the H146 cell line, which increased resistance to ABT-737, did not result in altered Mcl-1 levels. Therefore, three of four cell lines studied failed to show Noxa-mediated regulation of Mcl-1 expression. However, despite failure to regulate Mcl-1 levels, Noxa blocked binding of Bim to Mcl-1 following its release from Bcl-2 by ABT-737. Finally, we observed that a 24-hour incubation of the H526 and WBA cell lines with ABT-737 resulted in increased Noxa expression, suggesting that Noxa may play a direct role in ABT-737-mediated apoptosis. These results indicate that Noxa expression is the critical determinant of ABT-737 sensitivity and loss of Noxa-mediated regulation of Mcl-1 expression may be an important feature of small cell lung cancer biology.
Department of Medicine, Virginia Commonwealth Universityh and McGuire Veterans Affairs Medical Center (111K), 1201 Broad Rock Boulevard, Richmond, VA 23249, USA.
Paula
P
Hauck
Bo H
BH
Chao
Julie
J
Litz
Geoffrey W
GW
Krystal
D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D000072224:Bcl-2-Like Protein 11; D001713:Biphenyl Compounds / Q000494:pharmacology*; D015153:Blotting, Western; D049109:Cell Proliferation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm; D006801:Humans; D047468:Immunoprecipitation; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D008565:Membrane Proteins / Q000378:metabolism; D018716:Molecular Mimicry; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009596:Nitrophenols / Q000494:pharmacology*; D010446:Peptide Fragments; D010879:Piperazines / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055752:Small Cell Lung Carcinoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D013449:Sulfonamides / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
C501332:ABT-737; D051017:Apoptosis Regulatory Proteins; C000606775:BCL2L11 protein, human; C474007:Bax protein (53-86); D000072224:Bcl-2-Like Protein 11; D001713:Biphenyl Compounds; D008565:Membrane Proteins; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009596:Nitrophenols; C498702:PMAIP1 protein, human; D010446:Peptide Fragments; D010879:Piperazines; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D013449:Sulfonamides