Immunohistochemical study on pancreatic secretory trypsin inhibitor (PSTI) in gastric carcinomas

The expression of pancreatic secretory trypsin inhibitor (PSTI) was studied immunohistochemically in 106 cases of gastric carcinoma. Of the 45 intestinal-type carcinomas, 34 cases (76%) expressed PSTI: 15 (63%) of 24 early carcinomas and 19 (90%) of 21 advanced carcinomas, the incidence being significantly different (P less than 0.05). Furthermore, in the intestinal-type carcinomas, a significant correlation was observed between PSTI expression and clinical stage or nodal involvement. On the other hand, of the 61 diffuse-type carcinomas, including 27 early and 34 advanced carcinomas, 54 cases (89%) were positive for PSTI; a high incidence of the PSTI expression was observed in both early and advanced carcinomas, being 93% and 85%, respectively. Moreover, PSTI-positive cells were localized in more than half of the early diffuse-type gastric carcinomas at the invading zone of the surrounding tissues. The incidence of PSTI expression in advanced scirrhous-type carcinomas (100%) was significantly higher than that (76%) in medullary-type ones (P less than 0.05). Thus, the present findings, together with the previous reports that PSTI stimulates 3H-thymidine incorporation into DNA in human fibroblasts, suggest that the PSTI expressed in gastric carcinomas may possibly possess a biologic function responsible for the tumor growth and progression and for the stromal proliferation of fibrous tissues.