Rapamycin rescues ABT-737 efficacy in small cell lung cancer Academic Article uri icon


MeSH Major

  • Antineoplastic Combined Chemotherapy Protocols
  • Biphenyl Compounds
  • Lung Neoplasms
  • Nitrophenols
  • Sirolimus
  • Small Cell Lung Carcinoma
  • Sulfonamides


  • Overexpression of the antiapoptotic protein Bcl-2 is observed in the majority of small cell lung cancer (SCLC) cases and is associated with resistance to chemotherapy. While targeting Bcl-2 in hematologic malignancies continues to show signs of promise, translating the BH3 mimetic ABT-737 (or ABT-263; navitoclax) to the clinic for solid tumors has remained problematic, with limited single-agent activity in early-phase clinical trials. Here, we used patient-derived xenograft (PDX) models of SCLC to study ABT-737 resistance and demonstrated that responses to ABT-737 are short lived and coincide with decreases in HIF-1α-regulated transcripts. Combining the mTOR inhibitor rapamycin with ABT-737 rescued this resistance mechanism, was highly synergistic in vitro, and provided durable tumor regressions in vivo without notable hematologic suppression. In comparison, tumor regressions did not occur when ABT-737 was combined with etoposide, a gold-standard cytotoxic for SCLC therapy. Rapamycin exposure was consistently associated with an increase in the proapoptotic protein BAX, whereas ABT-737 caused dose-dependent decreases in BAX. As ABT-737 triggers programmed cell death in a BAX/BAK-dependent manner, we provide preclinical evidence that the efficacy of ABT-737 as a single agent is self-limiting in SCLC, but the addition of rapamycin can maintain or increase levels of BAX protein and markedly enhance the anticancer efficacy of ABT-737. These data have direct translational implications for SCLC clinical trials.

publication date

  • May 15, 2014



  • Academic Article



  • eng

PubMed Central ID

  • PMC4510983

Digital Object Identifier (DOI)

  • 10.1158/0008-5472.CAN-13-3460

PubMed ID

  • 24614082

Additional Document Info

start page

  • 2846

end page

  • 56


  • 74


  • 10