Identification Of MiRNA-dependent Regulatory Networks In Colorectal Cancer

MicroRNA (abbreviated miRNA) is a small non-coding RNA molecule (containing about 22 nucleotides) which functions post-transcriptionally. Because of this, these small molecules have very important roles in the regulation of eukaryotic gene expression. What's more, the expression of miRNA has differential spatial and temporal expression patterns. However, the regulatory networks of miRNA in colorectal cancer still remain uncoverd. In this study, we selected two miRNAs which played important roles in colorectal cancer and identified the regulation mechanism of these two miRNAs. Through miRNA sequencing and Northern blot analysis, we found that both miR-145 and miR-143 are stably down-regulated in colorectal cancer, while over-expression of miR-143 and miR-145 inhibited cancer cell proliferation, invasion and tumor growth. Further study was performed using in-lab developed algorithm KeyTar for mRNA target prediction and putative binding sites of miR-143 and miR-145 were predicted in the 3'UTR region of ErbB3, K-ras and N-ras, then we performed luciferase assay to confirm these identification. At the same time, Western blot showed that high expression of miR-143 could inhibit the expression of ERBB3 and K-ras while high expression of miR-145 could block the expression of N-ras. All these results demonstrated that miR-143 and miR-145 played important roles through inhibiting oncogenes in the occurrence and development of colorectal cancer.