Low expression of RSK4 predicts poor prognosis in patients with colorectal cancer.

BACKGROUND Colorectal cancer (CRC) is one of the leading causes of cancer-related death all over the world. Ribosomal s6 kinase4 (RSK4), an X-linked gene, firstly was found as to be a potential tumor suppressive gene in a variety of cancers and is widely participated in signaling pathway. However its role in CRC is unclear. This study is to explore the correlation between the protein expression of RSK4 and clinical pathologic characteristics in colorectal tumors, which might serve as a prognostic determinant of colorectal cancers. METHODS Biopsies of 103 colorectal cancer and 46 matched adjacent noncancerous tissues were collected for analysis of RSK4 protein by immunohistochemistry. The correlation between RSK4 protein expression and the clinical pathological features of colorectal cancers were evaluated by Chi-square test and Fisher's exact test. The survival rates were analyzed by the Kaplan-Meier method, and the relationship between prognostic factors and patient survival was analyzed by the Cox proportional hazard models. RESULTS RSK4 was conversely correlated with some pathological classifications (P<0.05 for N, G and clinical staging), and there were no statistically significant differences in age, CEA expression in blood, CA199 and tumors t-staging (x(2) test, P>0.05 for all categories) respectively. Furthermore, patients with high protein level of RSK4 showed prolonged overall survivals (P<0.05). Moreover, multivariate analysis showed that low expression level of RSK is an independent risk factor for high mortality in colorectal cancer. CONCLUSIONS Low RSK4 expression is correlated with advanced clinical pathologic classifications and is a poor overall survival in colorectal cancer patients. These findings suggest that RSK4 may serve as a useful marker in prognostic evaluation for patients with colorectal cancer.