Effect of camptothecin on inducible nitric oxide synthase expression in the colon cancer SW480 cell line

As a topoisomerase I inhibitor, camptothecin (CPT) is regarded as an effective antitumor agent. In an attempt to search for its novel anticancer mechanism, the present study evaluated the effects of CPT on inducible nitric oxide synthase (iNOS) in the human colon cancer SW480 cell line when stimulated with lipopolysaccharide (LPS) and interleukin (IL)-1 beta. The data indicated that CPT significantly decreased NO production. Consistent with these observations, the protein and mRNA expression levels of iNOS were inhibited by CPT in a dose-dependent manner. Thus, the inhibitory effects of CPT on LPS/IL-1 beta-stimulated NO production were likely mediated via the inhibition of iNOS gene transcription. From these results, we propose that the inhibition of NO biosynthesis by CPT may partially underlie the efficacy of this antitumor agent.