Identification of miR‐26b and miR‐203 gene targets in colon cancer cells

Abstract

We recently demonstrated that the unique combination of chemoprotective dietary fish oil (containing eicosapentaenoic acid and docosahexaenoic acid) plus pectin (fermented to butyrate in the colon) upregulates a subset of rat mucosal miRNAs, miR‐19b, miR‐26b and miR‐203, and downregulates their predicted target genes PTK2B, PDE4B and TCF4 as compared to a corn oil cellulose diet in the presence of carcinogen. To further elucidate the biological effects of diet and carcinogen on miRNAs and their targets and to validate the predicted miRNA:mRNA associations, we manipulated miRNA levels by conducting loss and gain of function analyses in the human colon cancer cell line HCT116 and measured changes in protein expression of the targets. Furthermore, using luciferase reporter assays, we demonstrated that PDE4B and TCF4 are direct targets of miR‐26b and miR‐203, while PTK2B is an indirect target of miR‐19b. In addition, the physiological function of these miRNAs was assessed by examining effects on apoptosis and cell proliferation, showing that these miRNAs increased apoptosis. This is the first report to show the chemoprotective effects of combined fish oil and pectin feeding antagonize the oncogenic effects of carcinogen, in part, by modulating the expression of colonic miR‐19b, miR‐26b and miR‐203 and their targets.Grant Funding Source: CPRIT grant RP100473 and NIH grants CA168312, CA129444 and CA59034.