TMEM16A/ANO1 inhibits apoptosis via down-regulation of Bim expression

Purpose: TMEM16A is a calcium-activated chloride channel that is amplified in a variety of cancers, including 30% of head and neck squamous cell carcinomas (HNSCC), raising the possibility of an anti-apoptotic role in malignant cells. The present study investigated this using a multi-modal, translational investigation. Experimental Design: Combination of 1) in vitro HNSCC cell culture experiments assessing cell viability, apoptotic activation, and protein expression 2) in vivo studies assessing similar outcomes, and 3) molecular and staining analysis of human HNSCC samples. Results: TMEM16A expression was found to correlate with greater tumor size, increased Erk 1/2 activity, less Bim expression, and less apoptotic activity overall in human HNSCC. These findings were corroborated in subsequent in vitro and in vivo studies and expanded to include a cisplatin-resistant phenotype with TMEM16A overexpression. A cohort of 41 patients with laryngeal cancer demonstrated that cases that recurred after chemoradiation failure were associated with a greater TMEM16A overexpression rate than HNSCC that did not recur. Conclusions: Ultimately, this study implicates TMEM16A as a contributor to tumor progression by limiting apoptosis and as a potential biomarker of more aggressive disease.

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