Prognostic implication of TSC1 and mTOR expression in gastric carcinoma

Background Gastric adenocarcinoma is the sixth most common and third most lethal cancer in the world. Except for HER2-targeted therapy, targeted agents against specific molecules participating in gastric carcinogenesis, including those in the mechanistic target of rapamycin (serine/threonine kinase) (mTOR) pathway have not been proved to be effective. However, some studies have suggested that dysfunction of TSC1 may augment mTOR inhibitor activity. Methods We studied p-mTOR and TSC1 status by immunohistochemical analysis of gastric carcinoma samples using a tissue microarray method and expression values adopted from The Cancer Genome Atlas. Results High p-mTOR and low TSC1 expression status is associated with adverse clinicopathologic parameters. Patients with high p-mTOR levels showed poor survival. Patients with low TSC1 levels showed unfavorable survival status in the overall patients group. The combination of p-mTOR status and TSC1 status provided more strong survival information than using each parameter alone. Conclusions In gastric cancer, high p-mTOR expression level is a statistically significant parameter in multivariate and Kaplan–Meier analyses (log-rank test). In addition to p-mTOR, TSC1 expression provided additional information to predict survival. We therefore suggest that evaluation of both p-mTOR and TSC1 status may be helpful in clinical trials related to mTOR inhibitors. J. Surg. Oncol. 2014 109:812–817. © 2014 Wiley Periodicals, Inc.