TY - JOUR
T1 - Reversal of mutant KRAS-mediated apoptosis resistance by concurrent Noxa/Bik induction and Bcl-2/Bcl-xL antagonism in colon cancer cells
AU - Okamoto, Koichi
AU - Zaanan, Aziz
AU - Kawakami, Hisato
AU - Huang, Shengbing
AU - Sinicrope, Frank A.
N1 - Publisher Copyright:
© 2014 American Association for Cancer Research.
PY - 2015/4/1
Y1 - 2015/4/1
N2 - KRAS mutations are frequently detected in human colorectal cancer and contribute to de novo apoptosis resistance and ultimately therapeutic failure. To overcome KRAS-mediated apoptosis resistance, the irreversible proteasome inhibitor, carfilzomib, was evaluated and found to potently induce Noxa, which was dependent upon c-Myc, and Bik. Isogenic mutant versus wild-type KRAS carcinoma cells showed elevated Bcl-xL, confirmed by KRAS siRNA or ectopic expression. Upregulated Bcl-xL by mutant KRAS was mediated by ERK as indicated by ERK knockdown. Bcl-xL expression was regulated at the level of mRNA and protein as shown using actinomycin D and cyclohexamide, respectively. Suppression of Bcl-xL by shRNA sensitized mutant KRAS cells to carfilzomib. Concurrent Bcl-xL antagonism by the BH3 mimetic ABT-263 combined with carfilzomib synergistically enhanced apoptosis that was dependent on Bax or p53, and was attenuated by Noxa or Bik shRNA. In support of this strategy, ectopically expressed Noxa enhanced apoptosis by ABT-263. Carfilzomib-induced Noxa and Bik sequestered Mcl-1 and ABT-263 released Bik and Bak from Bcl-xL, suggesting a mechanism for drug synergy. These preclinical findings establish mutant KRAS-mediated Bcl-xL upregulation as a key mechanism of apoptosis resistance in KRASmutant colorectal cancer. Furthermore, antagonizing Bcl-xL enabled carfilzomib-induced Noxa and Bik to induce synergistic apoptosis that reversed KRAS-mediated resistance.
AB - KRAS mutations are frequently detected in human colorectal cancer and contribute to de novo apoptosis resistance and ultimately therapeutic failure. To overcome KRAS-mediated apoptosis resistance, the irreversible proteasome inhibitor, carfilzomib, was evaluated and found to potently induce Noxa, which was dependent upon c-Myc, and Bik. Isogenic mutant versus wild-type KRAS carcinoma cells showed elevated Bcl-xL, confirmed by KRAS siRNA or ectopic expression. Upregulated Bcl-xL by mutant KRAS was mediated by ERK as indicated by ERK knockdown. Bcl-xL expression was regulated at the level of mRNA and protein as shown using actinomycin D and cyclohexamide, respectively. Suppression of Bcl-xL by shRNA sensitized mutant KRAS cells to carfilzomib. Concurrent Bcl-xL antagonism by the BH3 mimetic ABT-263 combined with carfilzomib synergistically enhanced apoptosis that was dependent on Bax or p53, and was attenuated by Noxa or Bik shRNA. In support of this strategy, ectopically expressed Noxa enhanced apoptosis by ABT-263. Carfilzomib-induced Noxa and Bik sequestered Mcl-1 and ABT-263 released Bik and Bak from Bcl-xL, suggesting a mechanism for drug synergy. These preclinical findings establish mutant KRAS-mediated Bcl-xL upregulation as a key mechanism of apoptosis resistance in KRASmutant colorectal cancer. Furthermore, antagonizing Bcl-xL enabled carfilzomib-induced Noxa and Bik to induce synergistic apoptosis that reversed KRAS-mediated resistance.
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U2 - 10.1158/1541-7786.MCR-14-0476
DO - 10.1158/1541-7786.MCR-14-0476
M3 - Article
C2 - 25548100
AN - SCOPUS:84928016878
SN - 1541-7786
VL - 13
SP - 659
EP - 669
JO - Molecular Cancer Research
JF - Molecular Cancer Research
IS - 4
ER -