Aberrant expression of microRNAs (miRNAs/miRs) is associated with the initiation and progression of colorectal cancer (CRC), but how they regulate colorectal tumorigenesis is still unknown. The present study was designed to investigate the expression profile of miRNAs in human CRC tissues, and to reveal the molecular mechanism of miRNA‑142‑3p in suppressing colon cancer cell proliferation. The expression of miRNA was examined using an Exiqon miRNA array. Bioinformatics was used to predict the target genes of differentially expressed miRNAs and to analyze their biological function in CRC. The effect of miR‑142‑3p in colon cancer cells was evaluated in vitro using cell proliferation, colony formation and Transwell assays. Dual‑luciferase reporter gene assays were performed to investigate the association between miR‑142‑3p and Rac family small GTPase 1 (RAC1). The effect of miR‑142‑3p regulation on colon cancer proliferation was assessed through western blotting and quantitative polymerase chain reaction analysis. Compared with their expression in adjacent non‑cancer mucosal tissues, 76 miRNAs were upregulated and 102 miRNAs were downregulated in CRC. One of the most significantly and differentially regulated miRNAs was miR‑142‑3p, which was downregulated in 81.0% (51/63) of primary CRC tissues. After transfection of miR‑142‑3p mimics into colon cancer cells, proliferation and colony formation were decreased, and migration and invasion were markedly suppressed. RAC1 was a possible target of miR‑142‑3p, which was confirmed by dual‑luciferase reporter assay. Transfection of miR‑142‑3p mimics decreased the levels of RAC1 and suppressed epithelial‑to‑mesenchymal transition in colon cancer cells. The phosphorylation of extraceullar signal‑regulated kinase (ERK) was decreased significantly by the inhibition of RAC1 or transfection of miR‑142‑3p mimics in colon cancer cells. In conclusion, aberrant miRNAs are implicated in CRC. Decreased expression of miR‑142‑3p may be associated with CRC tumorigenesis via Rac1‑ERK signaling.
Keywords: CRC; ERK1/2; RAC1; miRNA; miR‑142‑3p; microarray.