Mechanisms Of Long Non-Coding RNA And RNF6 Amplification Contributing To The Tumorigenesis And Chemoresistance Of Colorectal Cancer

The long non-codingRNA(LncRNA)colon cancer-associated transcript-1(LncRNA CCAT1)plays an important role in the development of various tumo rs including colorectal cancer(CRC).Previous studies have revealed that persis tent intestinal inflammation could increase the risk of CRC.But it remains und etermined that whether lncRNA CCAT1 is involved in inflammation and promo tes the malignant transformation of inflammatory bowel disease(IBD),and eve ntually results in the occurrence of CRC.This study aimed to explore the expr ession of lncRNA CCAT1 in colorectal tissue in patients with IBD and its effe ct on intestinal barrier function.First,we analyzed the lncRNA CCAT1 express ion profile of patients with inflammatory bowel disease and colorectal cancer i n the GEO(Gene Expression Omnibus,GEO)database,and found that inflam mation-related genes were enriched in the lncRNA CCAT1 high expression gro up,suggesting that lncRNA CCAT1 may regulate the inflammatory pathway.Se condly,further correlation analysis in IBD intestinal tissue indicated that the ex pression of lncRNA CCAT1 was positively correlated with the expression of m yosin light-chain kinase(MLCK)and negatively correlated with the expression of mi R-185-3p.Mechanism studies have found that lncRNA CCAT1 binded to mi R-185-3p in a Caco-2 monolayer model,resulting in reduced stability of the latter.Down-regulation of mi R-185-3p expression may result in up-regulation of MLCK expression,which in turn led to destruction of intestinal barrier func tion.In addition,we also found that the interaction between the main proteins ZO1(zonula occludens 1,ZO1)and Ocluddin as well as the actin ring in the intestinal epithelium were altered,showing a change in the relative position of the barrier protein.Therefore,we hypothesize that activation of lncRNA CCAT1/mi R-185-3p/MLCK pathway is an important mechanism leading to intestinal barrier destruction and accelerating IBD progression.Our study may provide ne w targeting molecules for IBD malignant transformation.DNA copy number variations are widely distributed in the human genome.It has been found that CNV in cancer cells may cause the activation of onco genes or the inactivation of tumor suppressor genes,and eventually contribute t o the tumorigenesis.We analyzed the expression profile of CNV-mRNA in Col orectal Cancer Genome Atlas(TCGA)database and identified one of E3 ubiqu itinated ligases,RNF6.The copy number was significantly amplified and RNF6 expression was highly expressed correspondingly in CRC tissues.Both amplifi cation and expression of RNF6 positively correlated with poor prognosis of pat ients with CRC.Further mechanism studies have shown that RNF6 induced the ubiquitination and degradation of SHP-1.As a result,p STAT3 level was incre ased accompanied with the JAK/STAT3 pathway activation.Up-regulation of R NF6 promoted the CRC cell proliferation and invasion in vitro and in vivo.Th erefore,this study provides a theoretical foundation for the patients with RNF6-amplifed CRC to adopt personalized treatment.Chemoresistance has become an important factor threatening the five-year survival rate of patients with advanced CRC.However,the molecular mechanis m of drug resistance in CRC remains to be explored.In this study,five pairs of colorectal cancers and paracancerous tissues were analyzed byRNA-sequenc e.A long non-codingRNA CACClnc was screened out.The results in vitro sh owed that CACClnc could promote chemoresistance of colorectal cancer cells.The mechanism may be related to the increased ability of homologous recombi nation.Our aim is to explore the detailed mechanism of CACClnc in chemores istance of CRC cells,and to provide new options for the diagnosis and treatm ent of colorectal cancer.