Aberrant Cell Proliferation by Enhanced Mitochondrial Biogenesis via mtTFA in Arsenical Skin Cancers

Arsenic-induced Bowen's disease (As-BD), a cutaneous carcinoma in situ, is thought to arise from gene mutation and uncontrolled proliferation. However, how mitochondria regulate the arsenic-induced cell proliferation remains unclear. The aim of this study was to clarify whether arsenic interfered with mitochondrial biogenesis and function, leading to aberrant cell proliferation in As-BD. Skin biopsy samples from patients with As-BD and controls were stained for cytochrome c oxidase (Complex IV), measured for mitochondrial DNA (mtDNA) copy number and the expression levels of mitochondrial biogenesis-related genes, including peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1 alpha), nuclear respiratory factor 1 (NRF-1), and mitochondrial transcription factor A (mtTFA). The results showed that expression of cytochrome c oxidase, mtTFA, NRF-1, and PGC-l alpha was increased in As-BD compared with in healthy subjects. Treatment of primary keratinocytes with arsenic at concentrations lower than 1.0 mu mol/L induced cell proliferation, along with enhanced mitochondrial biogenesis. Furthermore, we observed that the mitochondrial oxygen consumption rate and intracellular ATP level were increased in arsenic-treated keratinocytes. Blocking of mitochondrial function by oligomycin A (Complex V inhibitor) or knockdown of mtTFA by RNA interference abrogated arsenic-induced cell proliferation without affecting cyclin D1 expression. We concluded that mtTFA up-regulation, augmented mitochondrial biogenesis, and enhanced mitochondrial functions may contribute to arsenic-induced cell proliferation. Targeting mitochondrial biogenesis may help treat arsenical cancers at the stage of cell proliferation. (Am J Pathol 2011, 178:2066-2076; DOI: 10.1016/j.ajpath.2011.01.056)