Expression of differential nitric oxide synthase isoforms in human normal gastric mucosa and gastric cancer tissue

The present study investigated the expression and distribution of threeisoforms of nitric oxide synthase (NOS) in different anatomical regions ofthe human stomach and in gastric neoplastic tissues by immunohistochemistryusing specific antibodies. Intracellular localization of individualisoenzymes of NOS was detected in normal gastric mucosa. Gastric cancertissues had a marked reduction of all three NOS isoforms expression. Theexpression of the endothelial NOS, neuronal NOS and inducible NOS in thetumor tissue was significantly lower than in normal gastric mucosa (P =0.01, P = 0.02, P < 0.01, respectively). In the tumor tissue theexpression of inducible NOS was significantly lower than the expression ofboth constitutive forms of NOS (P < 0.01). There was a tendency tohigher expression of both constitutive forms of NOS in earlier stages T2 ofthe tumor compared to advanced T4 tumor. In contrast, the expression ofinducible NOS was higher than in the advanced T4 tumor than in the earlierstages T2 of the tumor. The mapping of the expression of endothelial NOS,neuronal NOS and inducible NOS in human stomach showed higher expression ofNOS isoforms in the distal third than in the proximal third of the stomach(P = 0.03, P = 0.04, P = 0.01, respectively). We conclude that there isgreater expression of NOS in the stomach corpus and in antrum than in theproximal third of the normal human stomach mirroring the anatomicalpredilection of common pathological changes in this part of the humanstomach. Furthermore, there was loss of the expression of individualisoenzymes in gastric neoplasms.