Tamoxifen Induces Oxidative Stress and Mitochondrial Apoptosis via Stimulating Mitochondrial Nitric Oxide Synthase

Abstract
Tamoxifen is an anticancer drug that induces oxidative stress and apoptosis via mitochondria-dependent and nitric oxide (NO)–dependent pathways. The present report shows that tamoxifen increases intramitochondrial ionized Ca2+ concentration and stimulates mitochondrial NO synthase (mtNOS) activity in the mitochondria from rat liver and human breast cancer MCF-7 cells. By stimulating mtNOS, tamoxifen hampers mitochondrial respiration, releases cytochrome c, elevates mitochondrial lipid peroxidation, increases protein tyrosine nitration of certain mitochondrial proteins, decreases the catalytic activity of succinyl-CoA:3-oxoacid CoA-transferase, and induces aggregation of mitochondria. The present report suggests a critical role for mtNOS in apoptosis induced by tamoxifen. [Cancer Res 2007;67(3):1282–90]