The Mechanism Of MiR-181a-5p Promotes The Progression Of Gastric Cancer Via Downregulation Of RASSF6

Objectives:We previously discovered that Ras association domain family member 6(RASSF6)was downregulated and predicted poor prognosis in gastric cancer patients.However,the mechanisms of the down regulation of RASSF6 in GC remained unclear.Increasing evidence indicates that dysregulation of micro RNAs promotesthe progression of cancer through the repression of tumour suppressors.The present investigation aims to clarify the exprssion level,clinical significance and mechanism of mi R-181a-5p and RASSF6 in gastric cancer.Methods:Base on the bioinformation analysis of The Cancer Genome Atlas,we identified mi R-181a-5p as a potential regulator of RASSF6 in GC.We used real time PCR and WB assays to detect expression level of mi R-181a-5p and RASSF6.Functionally,we construced ectopic expression or silencing of mi R-181a-5p and RASSF6 stable gastric cancer cell lines,respectively.Real time PCR,WB,tumor formation,CCK8,wound healing,plate clone formation,were used to detect the effect of mi R-181a-5p and RASSF6.We used the Kaplan-Meier survival curve method and multivariable Cox proptional hazards regression model to explore the correlation of mi R-181a-5p and RASSF6.We also used the receiver-operating characteristic curve method to evaluate the potential diagnostic value of mi R-181a-5p and RASSF6.Results:Real tine PCR and Western blot showed that mi R-181a-5p was more highly expressed in tumours with distant metastasis than in those without metastasis.Conversely,RASSF6 expression was lower in tumours with distant metastasis than in those without metastasis.Mi R-181a-5p promotes GC cell proliferation,wound healing,and invasion and induces EMT in vitro.Mi R-181a-5p facilitates invasion,metastasis and EMT of GC cells in vivo.Mi R-181a-5p activates the MAPK signalling pathway by directlyinhibiting the expression of RASSF6.The Kaplane-Meier analysis with a log rank test showed that high mi R-181a-5p predicted worse RFS in GC patients.The overall survival(OS)analyses of the data from the nonrecurrence and recurrence groups from the Shanghai General Hospital revealed that high mi R-181a-5p expression alone predicted poorer OS in the recurrence group,but not in the nonrecurrence patients.Furthermore,patients with high mi R-181a-5p expression and negative/weak RASSF6 staining had lower RFS and OS rates than those with lower mi R-181a-5p expression.Conclusion:We previously found that RASSF6 was down regulated in GC.Low RASSF6 predicted poor prognosis for GC patients.The present study further determined mi R-181a-5p to be a new modulator of RASSF6 in GC.High expression of mi R-181a-5p promoted the proliferation,invasion and peritoneal dissemination of metastasis of GC cells via RASSF6-mediated activation of the MAPK pathway in vitro and in vivo.More importantly,high mi R-181a-5p together with low RASS6 expression predicted poor prognosis in GC patients.