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Cancer Res. 2014 May 15;74(10):2846-56. doi: 10.1158/0008-5472.CAN-13-3460. Epub 2014 Mar 10.

Rapamycin rescues ABT-737 efficacy in small cell lung cancer.

Author information

1
Authors' Affiliations: Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine; Departments of Oncology and Neurosurgery, Johns Hopkins University School of Medicine, Baltimore, Maryland; and Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, New YorkAuthors' Affiliations: Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine; Departments of Oncology and Neurosurgery, Johns Hopkins University School of Medicine, Baltimore, Maryland; and Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, New York.
2
Authors' Affiliations: Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine; Departments of Oncology and Neurosurgery, Johns Hopkins University School of Medicine, Baltimore, Maryland; and Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, New York.
3
Authors' Affiliations: Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine; Departments of Oncology and Neurosurgery, Johns Hopkins University School of Medicine, Baltimore, Maryland; and Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, New YorkAuthors' Affiliations: Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine; Departments of Oncology and Neurosurgery, Johns Hopkins University School of Medicine, Baltimore, Maryland; and Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, New YorkAuthors' Affiliations: Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine; Departments of Oncology and Neurosurgery, Johns Hopkins University School of Medicine, Baltimore, Maryland; and Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, New York.
4
Authors' Affiliations: Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine; Departments of Oncology and Neurosurgery, Johns Hopkins University School of Medicine, Baltimore, Maryland; and Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, New York chann1@jhmi.edu.

Abstract

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.

PMID:
24614082
PMCID:
PMC4510983
DOI:
10.1158/0008-5472.CAN-13-3460
[Indexed for MEDLINE]
Free PMC Article

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