NOS1 and ovarian cancer: The present study determines if (1) basal protein levels of nitric oxide (NO) synthases (eNOS, iNOS, and nNOS) are different in cisplatin-sensitive (OV2008) and counterpart cisplatin-resistant (C13*) human ovarian cancer cells, (2) cisplatin alters NOS levels, (3) NO donor causes apoptosis and p53 upregulation, (4) NO donor sensitises C13* cells to cisplatin via p53 upregulation (determined by p53 siRNA gene-knockdown), and (5) inhibition of endogenous NOS alters cisplatin-induced apoptosis.