We hypothesised that basal sGC activity and regulation of p53 may depend on endogenous NO formed by one of the three NO synthases (NOSs), eNOS (also called NOS3), iNOS (also called NOS2), or nNOS (also called NOS1) and that resistance to CDDP in ovarian cancer cells may involve altered expression of the NOSs. Here, NOS1 is linked to ovarian cancer.