Preliminary Study On RSK4Function In Colorectal Cancer

The p90ribosomal S6kinases (RSK) is a family of intracellular serine-threonine kinases that are targets of downstream of mitogen-activated protein kinase (MAPK) extracellular signal-regulated kinase pathway. Four RSK members have been identified so f ar, that is, RSKs1,2,3and4. RSK family members RSK1, RSK2, and RSK3are the central mediators of extracellular signal-regulated kinase in the regulation of survival, growth, proliferation, invasion and metastasis via phosphorylation of numerous intracellular proteins including several transcription factors. The molecular and cellular level role of RSK1-3has been elaborated relatively clear. However, information on the abundance of RSK4in colorectum cancer tissues and cell lines is scarce and is quite conflicting. The formalin-fixed, paraffin-embedded pathology specimens of103colorectal cancer tissue samples,46matched adjacent noncancerous tissues were used as controls from the abovementioned patients. Pathological parameters, including age, gender, grade, nodal metastasis, clinical stage and survival data were carefully reviewed in all cases. Immunohistochemical assay in this study showed that RSK4expression is decreased in primary colorectal cancer tissues compared with their adjacent noncancerous tissues; the expression patterns of RSK4were correlated with clinic pathologic classifications of N, tumor grade and clinical staging; there was a significantly increased risk of cancer-related death in patients with low expression of RSK4using unvaried and multivariate Cox analysis. Morever, the test of quantitive Real time-PCR and Western Blot showed that the expression of RSK4is lower in colorectal cancer cells SW480and HCT116. After transfection of RSK4overexpression, MTT assay detected that RSK4could significantly inhibit the growth of colorectal cancer cells in vitro, this inhibitory peak effect from48hours to60hours; flow cytometry detected that S phase cells decreased significantly, GO/1cells increased significantly; transwell invasion assay showed that after transfection RSK4, SW480and HCT116cell line invasion was significantly lower than that in the control group. The results showed that RSK4could be an important role in tumor invasion and metastasis. As we all known, Tumor invasion and metastasis of tumor mesenchymal epithelial transition are inseparable. In this article,we have chosen EMT related molecular Claudin-2, E-cadherin, P53, Snail, TGF-β, Twist and Vimentin for the experiments. Expression of mRNA and protein of all relevant EMT molecules were analyzed after RSK4gene transfected successfully. It was found that mRNA of E-cadherin transfected RSK4group showed high expression, Snail showed low expression, and Claudin-2, P53, TGF-β, Twist, Vimentin little change in SW480, HCT116two cell lines. Expression of the protein of these EMT related molecular present a similar situation. Tumor invasion and metastasis about RSK4may be reduced by regulating E-cadherin and Snail. This study confirmed that the RSK4may be a tumor suppressor gene in colorectal cancer, would provide a new exploration and expect to become another effective therapeutic target of invasion and metastasis for colorectal cancer.