ABSTRACT
The platinum-based DNA damaging agent cisplatin is used as a standard therapy for locally advanced head and neck squamous cell carcinoma (HNSCC). However, the mechanisms underpinning the cytotoxic effects of this compound are not entirely elucidated. Cisplatin produces anticancer effects primarily via activation of the DNA damage response, followed by inducing BCL-2 family dependent mitochondrial apoptosis. We have previously demonstrated that cisplatin induces the expression of proapoptotic BCL-2 family protein, Noxa, that can bind to the prosurvival BCL-2 family protein, MCL-1, to inactivate its function and induce cell death. Here, we show that the upregulation of Noxa is critical for cisplatin-induced apoptosis in p53-null HNSCC cells. This induction is regulated at the transcriptional level. With a series of Noxa promoter-luciferase reporter assays, we find that the CRE (cAMP response element) in the promoter is critical for the Noxa induction by cisplatin treatment. Among the CREB/ATF transcription factors, ATF3 and ATF4 are induced by cisplatin, and downregulation of ATF3 or ATF4 reduced cisplatin-induced Noxa. ATF3 and ATF4 bind to and cooperatively activate the Noxa promoter. Furthermore, ERK1 is involved in cisplatin-induced ATF4 and Noxa induction. In conclusion, ATF3 and ATF4 are important regulators that induce Noxa by cisplatin treatment in a p53-independent manner.
Subject(s)
Activating Transcription Factor 3/metabolism , Activating Transcription Factor 4/metabolism , Cisplatin/pharmacology , Proto-Oncogene Proteins c-bcl-2/metabolism , Squamous Cell Carcinoma of Head and Neck/metabolism , Tumor Suppressor Protein p53/metabolism , Apoptosis/drug effects , Cell Line, Tumor , Extracellular Signal-Regulated MAP Kinases/metabolism , Gene Expression Regulation, Neoplastic/drug effects , Humans , Models, Biological , Promoter Regions, Genetic , Protein Binding/drug effects , Proto-Oncogene Proteins c-bcl-2/genetics , RNA, Messenger/genetics , RNA, Messenger/metabolism , Signal Transduction/drug effects , Squamous Cell Carcinoma of Head and Neck/genetics , Squamous Cell Carcinoma of Head and Neck/pathologyABSTRACT
Purpose: Small-cell lung cancer (SCLC) is an often-fatal neuroendocrine carcinoma usually presenting as extensive disease, carrying a 3% 5-year survival. Despite notable advances in SCLC genomics, new therapies remain elusive, largely due to a lack of druggable targets.Experimental Design: We used a high-throughput drug screen to identify a venetoclax-sensitive SCLC subpopulation and validated the findings with multiple patient-derived xenografts of SCLC.Results: Our drug screen consisting of a very large collection of cell lines demonstrated that venetoclax, an FDA-approved BCL-2 inhibitor, was found to be active in a substantial fraction of SCLC cell lines. Venetoclax induced BIM-dependent apoptosis in vitro and blocked tumor growth and induced tumor regressions in mice bearing high BCL-2-expressing SCLC tumors in vivo BCL-2 expression was a predictive biomarker for sensitivity in SCLC cell lines and was highly expressed in a subset of SCLC cell lines and tumors, suggesting that a substantial fraction of patients with SCLC could benefit from venetoclax. Mechanistically, we uncover a novel role for gene methylation that helped discriminate high BCL-2-expressing SCLCs.Conclusions: Altogether, our findings identify venetoclax as a promising new therapy for high BCL-2-expressing SCLCs. Clin Cancer Res; 24(2); 360-9. ©2017 AACR.
