Effect of rs67085638 in long non-coding RNA (CCAT1) on colon cancer chemoresistance to paclitaxel through modulating the microRNA-24-3p and FSCN1 signaling

Abstract

BackgroundIt has been reported that rs67085638 in lncRNA-CCAT1 was associated with the risk of tumorigenesis. Also, CCAT1 could affect chemoresistance of cancer cells to PTX via regulating miR-24-3p and FSCN1 expression. In this study, we aimed to investigate the effect of rs67085638 on the expression of CCAT1/miR-24-3p/FSCN1 and the response of colon cancer to the treatment of PTX.Method48 colon cancer patients were recruited and grouped by their genotypes of rs67085638 polymorphism as a CC group (N=28) and a CT group (N=20). Colon cancer cells were collected from the patients and cancer cell xenografts were transplanted into mice. PCR analysis, IHC assay and Western blot were performed to observe the expression of lncRNA-CCAT1, miR-24-3p and FSCN1 in vivo and in vitro, and the relationships among the expression of lncRNA-CCAT1, miR-24-3p and FSCN1 were validated by computational analysis and luciferase assay. TUNEL assay and flow cytometry were conducted to observe tumor cell apoptosis and survival.ResultLncRNA-CCAT1 and FSCN1 mRNA/protein were over-expressed while miR-24-3p was down-regulated in the CT-genotyped patients and cells compared with those in the CC-genotyped patients and cells. The survival of colon cancer cells was decreased while the apoptosis of colon cancer cells was increased by PTX treatment in a dose-dependent manner. However, the survival rate of CT-genotyped cells was higher while the apoptosis rate of CT-genotyped cells was lower than that of the CC-genotyped cells, and the difference was partly eliminated by the knockdown of lncRNA-CCAT1. MiR-24-3p was validated to target lncRNA-CCAT1 and FSCN1 mRNA, and the over-expression of CCAT1 could reduce the expression of miR-24-3p while elevating the expression of FSCN1. The growth of CT-genotyped tumors in mice was more suppressed in compared with the growth of CC-genotyped tumors, while the knockdown of lncRNA-CCAT1 partly reversed the effect of the CT genotype. Furthermore, compared with the rs67085638-CC mice, the lncRNA-CCAT1 and FSCN1 mRNA/protein levels in the rs67085638-CT+NC shRNA mice were increased while their miR-24-3p level was decreased, and the knockdown of lncRNA-CCAT1 partly reversed the dysregulation of these genes.ConclusionThe findings of this study demonstrated that the presence of the minor allele of rs67085638 increased the expression of CCAT1 and accordingly enhanced the resistance to PTX. Downregulation of CCAT1 partially, but significantly, re-stored the sensitivity to PTX of colon cancer cells.