Combination treatment with ABT-737 and chloroquine in preclinical models of small cell lung cancer.

BACKGROUND: New therapies are urgently needed for patients with small cell lung cancer (SCLC). Chemotherapy and targeted therapies, including the Bcl-2 inhibitor ABT-737, may induce tumor cell autophagy. Autophagy can promote survival of cancer cells under stress and comprise a pathway of escape from cytotoxic therapies. METHODS: We explored the combination of ABT-737 and chloroquine, an inhibitor of autophagy, in preclinical models of SCLC. These included cell culture analyses of viability and of autophagic and apoptotic pathway induction, as well as in vivo analyses of efficacy in multiple xenograft models. RESULTS: Combination treatment of SCLC lines with ABT-737 and chloroquine decreased viability and increased caspase-3 activation over treatment with either single agent. ABT-737 induced several hallmarks of autophagy. However, knockdown of beclin-1, a key regulator of entry into autophagy, diminished the efficacy of ABT-737, suggesting either that the effects of chloroquine were nonspecific or that induction but not completion of autophagy is necessary for the combined effect of ABT-737 and chloroquine. ABT-737 and chloroquine in SCLC cell lines downregulated Mcl-1 and upregulated NOXA, both of which may promote apoptosis. Treatment of tumor-bearing mice demonstrated that chloroquine could enhance ABT-737-mediated tumor growth inhibition against NCI-H209 xenografts, but did not alter ABT-737 response in three primary patient-derived xenograft models. CONCLUSION: These data suggest that although ABT-737 can induce autophagy in SCLC, autophagic inhibition by choroquine does not markedly alter in vivo response to ABT-737 in relevant preclinical models, arguing against this as a treatment strategy for SCLC.

Food and Drug Administration Beyond the 2001 Government Accountability Office Report: Promoting Drug Safety for Women.

A 2001 U.S. Government Accountability Office (GAO) report indicated 8 of 10 drugs withdrawn from the U.S. market between 1997 and 2000 posed greater risk to women than men. We examined drugs withdrawn from the market for safety-related reasons from January 1, 2001, to January 1, 2018. To be included, drugs must be listed as discontinued on Drugs@FDA and either listed in the Federal Register or cited in literature as being withdrawn for safety-related reasons. Biologics, over-the-counter products, and medical devices were excluded. During the 17-year time span, 19 drugs were withdrawn from the market for safety-related reasons, fewer drugs per year compared to the 3-year period examined in the GAO report. Food and Drug Administration (FDA) has not recommended the market removal of any drug approved since 2005 due to the time from the start of the Q wave to the end of the T wave (QT) interval prolongation resulting in torsades de pointes (TdP) or other abnormal heart rhythms. Furthermore, no drugs approved after the implementation of FDA's 2009 guidance on drug-induced liver injury (DILI) have been withdrawn because of hepatoxicity. All, but one of the drugs discontinued from the market for safety-related reasons during the period examined were approved between 1957 and 2002. TdP and DILI are two relevant examples of drug-induced adverse events posing greater risk to women than men. FDA has made measurable progress incorporating consideration of sex and gender differences into drug trial development and FDA review of these data, supporting inclusion of women in clinical trials, providing a comprehensive drug safety review, and advancing postmarket surveillance and risk assessment, thus strengthening FDA's ability to protect public health.

Inhibition of SIRT1 reactivates silenced cancer genes without loss of promoter DNA hypermethylation.

The class III histone deactylase (HDAC), SIRT1, has cancer relevance because it regulates lifespan in multiple organisms, down-regulates p53 function through deacetylation, and is linked to polycomb gene silencing in Drosophila. However, it has not been reported to mediate heterochromatin formation or heritable silencing for endogenous mammalian genes. Herein, we show that SIRT1 localizes to promoters of several aberrantly silenced tumor suppressor genes (TSGs) in which 5' CpG islands are densely hypermethylated, but not to these same promoters in cell lines in which the promoters are not hypermethylated and the genes are expressed. Heretofore, only type I and II HDACs, through deactylation of lysines 9 and 14 of histone H3 (H3-K9 and H3-K14, respectively), had been tied to the above TSG silencing. However, inhibition of these enzymes alone fails to re-activate the genes unless DNA methylation is first inhibited. In contrast, inhibition of SIRT1 by pharmacologic, dominant negative, and siRNA (small interfering RNA)-mediated inhibition in breast and colon cancer cells causes increased H4-K16 and H3-K9 acetylation at endogenous promoters and gene re-expression despite full retention of promoter DNA hypermethylation. Furthermore, SIRT1 inhibition affects key phenotypic aspects of cancer cells. We thus have identified a new component of epigenetic TSG silencing that may potentially link some epigenetic changes associated with aging with those found in cancer, and provide new directions for therapeutically targeting these important genes for re-expression.

hTERT is expressed in cancer cell lines despite promoter DNA methylation by preservation of unmethylated DNA and active chromatin around the transcription start site.

hTERT, which encodes the catalytic subunit of telomerase and is expressed in most immortalized and cancer cells, has been reported to have increased DNA methylation in its promoter region in many cancers. This pattern is inconsistent with observations that DNA methylation of promoter CpG islands is typically associated with gene silencing. Here, we provide a comprehensive analysis of promoter DNA methylation, chromatin patterns, and expression of hTERT in cancer and immortalized cells. Methylation-specific PCR and bisulfite sequencing of the hTERT promoter in breast, lung, and colon cancer cells show that all cancer cell lines retain alleles with little or no methylation around the transcription start site despite being densely methylated in a region 600 bp upstream of the transcription start site. By real-time reverse transcription-PCR, all cancer cell lines express hTERT. Chromatin immunoprecipitation (ChIP) analysis reveals that both active (acetyl-H3K9 and dimethyl-H3K4) and inactive (trimethyl-H3K9 and trimethyl-H3K27) chromatin marks are present across the hTERT promoter. However, using a novel approach combining methylation analysis of ChIP DNA, we show that active chromatin marks are associated with unmethylated DNA, whereas inactive marks of chromatin are associated with methylated DNA in the region around the transcription start site. These results show that DNA methylation patterns of the hTERT promoter (-150 to +150 around the transcription start) are consistent with the usual dynamics of gene expression in that the absence of methylation in this region and the association with active chromatin marks allow for the continued expression of hTERT.

ERK phosphorylation is predictive of resistance to IGF-1R inhibition in small cell lung cancer.

New therapies are critically needed to improve the outcome for patients with small cell lung cancer (SCLC). Insulin-like growth factor 1 receptor (IGF-1R) inhibition is a potential treatment strategy for SCLC: the IGF-1R pathway is commonly upregulated in SCLC and has been associated with inhibition of apoptosis and stimulation of proliferation through downstream signaling pathways, including phosphatidylinositol-3-kinase-Akt and mitogen-activated protein kinase. To evaluate potential determinants of response to IGF-1R inhibition, we assessed the relative sensitivity of 19 SCLC cell lines to OSI-906, a small molecule inhibitor of IGF-1R, and the closely related insulin receptor. Approximately one third of these cell lines were sensitive to OSI-906, with an IC50 < 1 µmol/L. Cell line expression of IGF-1R, IR, IGF-1, IGF-2, IGFBP3, and IGFBP6 did not correlate with sensitivity to OSI-906. Interestingly, OSI-906 sensitive lines expressed significantly lower levels of baseline phospho-ERK relative to resistant lines (P = 0.006). OSI-906 treatment resulted in dose-dependent inhibition of phospho-IGF-1R and phospho-Akt in both sensitive and resistant cell lines, but induced apoptosis and cell-cycle arrest only in sensitive lines. We tested the in vivo efficacy of OSI-906 using an NCI-H187 xenograft model and two SCLC patient xenografts in mice. OSI-906 treatment resulted in 50% tumor growth inhibition in NCI-H187 and 30% inhibition in the primary patient xenograft models compared with mock-treated animals. Taken together our data support IGF-1R inhibition as a viable treatment strategy for a defined subset of SCLC and suggest that low pretreatment levels of phospho-ERK may be indicative of sensitivity to this therapeutic approach.