['13-Methyltetradecanoic acid (13-MTD), a saturated branched-chain fatty acid purified from soy fermentation products, is known to induce apoptosis in many types of human cancer cells. This study was designed to investigate the molecular mechanisms involved in 13-MTD-induced apoptosis in human bladder cancer cells.', 'MTT assay was used to investigate the potential effects of 13-MTD on the growth and viability of human bladder cancer cells. To find out whether anti-proliferation and cell death were associated with apoptosis, we used flow cytometry to quantify the extent of apoptosis and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay to measures DNA degradation of apoptotic cells. The proteins involved in the 13-MTD induced apoptosis were examined using Western blot.', 'We show that 13-MTD inhibits cellular proliferation and viability in human bladder cancer cells, which has been attributed to apoptosis. 13-MTD down-regulates Bcl-2 and up-regulates Bax. This promotes mitochondrial dysfunction, leading to the release of cytochrome c from the mitochondria to the cytoplasm, as well as the proteolytic activation of caspases. Moreover, 13-MTD down-regulates AKT phosphorylation and activates phosphorylation of p38 and c-Jun N-terminal kinase (JNK). Up-regulating AKT phosphorylation and down-regulating JNK and P38 phosphorylation could attenuate the13-MTD-induced apoptosis.'] Does 13-Methyltetradecanoic acid induce mitochondrial-mediated apoptosis in human bladder cancer cells?