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.
Hauck
Paula
P
Department of Medicine, Virginia Commonwealth Universityh and McGuire Veterans Affairs Medical Center (111K), 1201 Broad Rock Boulevard, Richmond, VA 23249, USA.
Chao
Bo H
BH
Litz
Julie
J
Krystal
Geoffrey W
GW
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