hsa-miR-497 as a modulator of the expression in the presence or absence of chrna5 in breast cancer

CHRNA5 is an important ligand-gated receptor with roles in addiction and in cancer. In lung cancer, CHRNA5 dysregulation is well known. There is also expression of CHRNA5 in breast cancer cell lines. microRNAs regulate mRNA expression; and different regulatory microRNAs are involved in different cancer types. microRNAs are thus potential biomarkers to diagnose the diseases (e.g. cancer). However, there is no study testing interactions between microRNAs and CHRNA5 in breast cancer. In the present study, mir-497 was found to be one of the most downregulated microRNAs with testable expression levels upon analysis of expression in the breast cancer cell line MCF7 when exposed to CHRNA5 siRNA. RT-qPCR was performed to test the expression level of mir-497. Validated target genes of mir-497 were found to be significantly related to a list of different KEGG pathways significantly (p value < 0.001) among which there were P53 and PI3K-Akt signalling pathways. Mimic-mir-497 treatment, alone or together with CHRNA5 siRNA, was applied on MCF7 cells to understand the interaction between the miRNA and siRNA under investigation. Selected target genes of mir-497 were tested; the most significantly modulated genes were involved in P53 pathway. The results indicated interactions between mir-497 and CHRNA5 however selected targets were not affected by mimicmir- 497. GSE41079 and GSE41074 public datasets containing mRNA and microRNA expression profiles of liver cancer cells treated with mimic-mir-497. Treatment were used to identify novel targets of mir-497 for future use. Immune system was detected in the second place upon REACTOME analysis of GSE41079 and GSE41074. Using multiple online microRNA-mRNA network tools mir-497 mRNA-miRNA networks were extracted for all or only immune genes. The results from network based analyses helped identify additional targets for later use in our mimic-siRNA system.