Comprehensive Analysis Of Differentially Expressed mRNAs and miRNAs In Breast Cancer

Abstract

Breast cancer is the second highest leading cause of mortality among women. There are many factors responsible for promoting breast cancer. One of the risk factor of this malignancy is molecular alterations. The molecular alterations include epigenetic regulations such as regulation by microRNAs (miRNAs). miRNAs are a group of small non-coding RNAs, about 18-25 nucleotides in length. These miRNAs have the potential to regulate mRNA expression by suppressing the translational activity. In this study, we aim to identify miRNAs which might have a role in breast cancer. For this, we analyzed expression data of miRNAs and mRNAs in breast cancer tissues and identified the sets of miRNAs and mRNAs that are differentially expressed in breast cancer. Considering sets of up-regulated miRNA and down-regulated mRNAs, we constructed miRNA-target interaction map and screened few miRNA-target pairs (hsa-miR-27a-3p:ADAMTS5 & hsa-miR-17-5p: CX3CL1) that are hypothesised to play a role in breast cancer malignancy. To confirm the expression of these miRNAs and mRNAs in breast cancer, we performed qRT-PCR of each of the mRNAs and miRNAs in MDA-MB-231 cell line and found that miRNAs- hsa-miR-27a-3p, hsa-miR-17- 5p that target ADAMTS5 and CX3CL1 respectively are up-regulated and the corresponding targets are down-regulated. This inverse correlation in expression of these miRNAs and mRNAs supplemented with presence of target sites identified from target prediction indicate that these two miRNAs might be regulating the expression of these two mRNAs which in turn might be playing a crucial role in breast cancer. miRNA targeting can be further confirmed by luciferase reporter assays. We also performed methylation specific PCR (MSP) of ADAMTS5 to find the possibility whether its expression is modulated by methylation, rather than miRNAs before proceeding for reporter assays.