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 < 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 < 0.05). Thus, the present findings, together with the previous reports that PSTI stimulates 3H-thymidine incorporation into DNA in human fibroblasts, suggest that 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.