PO-355 Antitumor activity of HSA-miR-X in HER2 positive cells is mediated by the regulation of AKT and ERK

Abstract

IntroductionHER2 overexpression has been reported in approximately 30% of human breast tumours, and is associated with poor clinical outcome and recurrent disease. Herceptin is a humanised monoclonal antibody targeting HER2. PI3K-AKT is a downstream effector of the HER2 signalling pathway. microRNAs (miRNA) are small non-coding RNAs of 19–22 nucleotides that can negatively regulate gene expression at post-transcriptional levels. Herceptin plays an important role in treating metastatic breast cancer by targeting Erbb2 (HER2), therefore, combining Herceptin with miRNAs might enhance its antitumor activity. In this study the antitumor activity of hsa-miR-X, which was found to be Herceptin–responsive by our group, with Herceptin in HER2 positive breast cancer cell lines was identified in SK-Br-3 and BT-474 cells.Material and methodsWe investigated the synergistic effect of Herceptin and miRNA mimic combination on tumorigenic activities of the cells. To check its role in migration and invasion, wound healing and invasion assays were performed respectively. Cell invasion was monitored over a period of 24 hours by xCELLigence real-time cell analyzer measuring impedance-based signals. Furthermore, viability of breast cancer cells was measured by the WST1 assay after transfection with hsa-miR-X miRNA mimic. We measured the expression of AKT and ERK in HER2 positive cells treated with miR-X mimic plus Herceptin by Western blot analysis.Results and discussionsWe showed that increased expression of hsa-miR-X significantly inhibits migration and invasion of HER2 (+) breast cancer cells. Additionally, western blot experiments demonstrated that transfection of hsa-miR-X with Herceptin treatment decreased the protein level of AKT and ERK in these cells.ConclusionIt may be concluded that hsa-miR-X may increase the activity of the drug by pulling down its effective concentration and regulating PI3K-AKT pathway in HER2 positive cells. hsa-miR-X could decrease proliferation, motility and invasion via inhibiting Akt phosphorylation and may represent a new strategy for treating HER2 positive breast cancer.