Differential expression of nitric oxide synthase in human stomach cancer

The level of expression and cellular localization of isoenzymes of nitric o xide synthase (NOS) was detected in human stomach tumor tissues. Tumor tiss ues showed 70% higher activity of NOS than that of normal tissues (P < 0.01 ). Poorly differentiated adenocarcinoma tend to have higher activity (P < 0 .05) than well differentiated and moderately differentiated tumor tissues. Aminoguanidine (AG), 2-amino-5,6-dihydro-6-methyr-4H-1,3-thiazine (AMT), N- G-monomethyl-L-arginine (L-NMMA), and N-omega-nitro-L-arginine (L-NNA) inhi bited NOS activity in tumor tissues by 18, 14, 11 and 13%, respectively. Th e TNF-alpha mRNA expression was correlated with the inducible NOS (iNOS) le vel, which was high in adenocarcinomas and low in normal tissues. Tumor tis sues showed higher expression of iNOS in gland epithelial cells but the lev er of eNOS was significantly decreased with an exception of concentrated lo calization in the proliferating capillary endothelium. These results reveal ed that isoforms of NOS might contribute differentially to growth and progr ession of human stomach tumor. (C) 1999 Elsevier Science Ireland Ltd. All r ights reserved.