The Function Of MicroRNA-150and MicroRNA-495in Tumourgenesis

MicroRNAs (miRNAs) are a class of endogenously expressed, small non-coding RNAs with the length of19-23nt. Through base-pairing with3’-untranslated region (3’-UTR) of messenger RNA (mRNA), miRNAs depress expression of target genes at the post-transcriptional level by inhibiting translation of mRNA or by destabilizing mRNA. Under the normal circumstance, miRNAs are involved in a variety of basic biological processes, such as development, proliferation, differention, apotosis and stress responses. In recent years, deregulated expression of miRNAs has been reported to be assaciated with many diseases, such as cancer.In the first part, we investigated the role of miR-150in lung cancer progress. MiR-150was found to be significantly upregulated in lung cancer clinical specimens by quantitative RT-PCR. Using bioinformatics analysis, SRC kinase signaling inhibitor1(SRCIN1), an important regulator of SRC activity, was predicted to be a potential target of miR-150. Accordingly, protein level of SRCIN1was found downregulated in human lung cancer tissue samples, which resulted in enhancement of Src activity. It was further confirmed that miR-150directly recognizes3’-UTR of SRCIN1transcript with a luciferase reporter assay. Then, decline or rise of SRCIN1protein level was detected when overexpressing or down-regulating miR-150in lung cancer cell lines, which led to the change of Src activity, Src/FAK and Src/Ras/ERK singaling pathway, and eventually promoted or inhibited the proliferation and migration of A549cells. And the promotion of migration of A549cells by miR-150could be reversed by overexpressing SRCIN1ORF (open reading frame) vector, which was not regulated by miRNA for lacking3’-UTR.In the second part, we investigated the role of JAM-A and miR-495in breast cancer metastasis. First, it was demonstrated that JAM-A was downregulated in breast cancer clinical specimens and the protein level of JAM-A was negatively correlated the mobility of breast cancer cells by Transwell assay and wound healing assay. Then knocking-down of JAM-A was accomplished by transfecting JAM-A siRNA in MCF-7cells, which was associated with promotion of mobility of MCF-7cells. And overexpression of JAM-A was accomplished by transfecting JAM-A ORF vector into MDA-MB-231cells, which revealed an inhibition of MDA-MB-231cell’s mobility. In silico approach predicted that miR-495could regulate the expression of JAM-A by binding to3’-UTR of JAM-A mRNA, which then was proved by a luciferase reporter assay. Accordingly, miR-495level was found to be upregulated in breast cancer tissue samples. It was further confirmed that repression or elevation of JAM-A protein level was detected when overexpressing or down-regulating miR-495in MCF-7and MDA-MB-231cells, which resulted in promotion or inhibition of the migration ability of these breast cancer cells. And the promotion of MCF-7cells’ mobility by miR-495could be reversed by overexpressing JAM-A ORF vector.In summary, deregulation of miRNAs was found to be highly associated with cancer progression. For example, miR-150and miR-495were upregulated in lung cancer and breast cancer respectively, and functioned as oncogenes by regulating proliferation or migration of tumour cells. These studies expanded the role of miRNAs in tumourgenesis, and provided new targets for the researches and therapies of cancer.