THE EXPRESSION OF STAT91, RAS-INDEPENDENT SIGNAL TRANSDUCER AND ACTIVATOR, IN HUMAN GASTRIC CARCINOMAS

Upon binding of interferon (IFN) and epidermal growth factor (EGF) to their cell surface receptors, tyrosine phosphorylation of latent cytop lasmic Stat91 (Ras-independent signal transducer and activator of tran scription, Stat1 alpha) protein is promptly induced and translocate fr om the cytoplasm to the nucleus to transduce the signal. The expressio n of mRNA for Stat91 was examined in 8 gastric carcinoma cell lines an d 21 gastric carcinoma tissues as well as corresponding normal mucosa. Of the 8 gastric carcinoma cell lines, all expressed a 4.7 kb Stat91 mRNA and a 91 kD protein at various levels. In gastric carcinoma cell lines, the levels of Stat91 mRNA expression were compatible with those of Stat91 protein expression. In surgical cases, all the gastric carc inoma tissues and their adjacent non-neoplastic mucosa expressed Stat9 1 mRNA and protein. Interestingly, 14 (66%) out of 21 tumors expressed Stat91 mRNA at higher levels than their corresponding normal mucosas. Moreover, 6 (75%) of 8 tumor tissues expressed higher levels of Stat9 1 protein as compared with those of the corresponding normal gastric m ucosa. No significant correlation was detected between the expression of Stat91 and clinicopathological feature of gastric carcinoma. These results suggest that the majority of gastric cancer in vivo harbour ov erexpression of Stat91 as a signal transducer in response to various c ytokines or growth factors which may be implicated in the growth of ga stric cancer.