STAT3 expression in gastric cancer indicates a poor prognosis

Signal transducers and activators of transcription (STAT) behave as signal transducers in the cytoplasm and as transcription factors in the nucleus. In the current study, we analyzed the immunohistochemical staining patterns of gastrectomy tissue specimens. We investigated the expression of STAT3 and STAT5 and estimated the relationship between STAT and cancer prognosis. One hundred patients who underwent gastrectomy due to gastric adenocarcinoma at Bundang CHA hospital between January 2000 and May 2005 were studied. Immunohistochemistry was carried out using antibodies against STAT3 and STAT5. The interpretation of the immunohistochemical staining was based on the proportion of stained cells in the field: positive, > 10% stained cells; and negative, < 10% stained cells. The longest diameter of tumor was 4.67 cm in the positive group and 3.76 cm in the negative group, and these results were not statistically different (P-value = 0.112). Higher T (primary tumor) value (P-value = 0.05), more regional lymph node invasion (P-value = 0.008) and higher TNM staging (P-value = 0.069) were significantly related to STAT3 positivity, but Helicobacter pylori infection or atrophic gastritis were not related. A lower survival rate was observed in the STAT3-positive group (P-value = 0.001). The results of STAT5 were not statistically different with respect to TNM staging and survival (P-value = 0.958). We thus report that the immunohistochemical results of STAT3 revealed a significant association with TNM staging and survival. We anticipate that STAT3 may be used as a molecular staging biomarker predicting poor prognosis of gastric cancer.