Abstract
miRNAs may play effective roles in breast cancer so modulating their expression levels could have therapeutic benefits. Recent studies have found the combination of miRNA-based therapeutics with conventional drugs as promising. This study aimed to find drug-responsive miRNAs, and explore their anticancer activities in HER2+ breast cancer cells and regulatory role in the trastuzumab response. qRT-PCR-array analysis was performed with effective concentrations of tamoxifen and trastuzumab treated BT-474, SK-BR-3 and MCF-7 cells. Motility and invasion analyses were performed with wound healing and xCELLigence impedance-based assays respectively. Viability of cells following mimic transfection and drug treatment was assessed by WST-1 assay. Western blot analysis was used to assess miR-770-5p regulation of proteins and their phosphorylated forms. The clinical relevance of miR-770-5p was examined by TCGA data analysis. The qRT-PCR-array results indicated that miR-770-5p was responsive in a drug and cell line independent manner. Overexpression of miR-770-5p inhibited the motility and cell invasion through regulation of AKT and ERK proteins. Additionally, miR-770-5p potentiated the effectiveness of trastuzumab. Thus, regulating the expression level of miR-770-5p in combination with trastuzumab treatment may simultaneously inhibit the downstream elements of PI3K and MAPK signalling, thereby blocking the proliferation, motility and invasion capacities of HER2+ breast cancer cells.
Highlights
Breast cancer is the most common malignancy in women, constituting approximately 30% of all cancer types [1]
The putative roles of miRNAs in tamoxifen or trastuzumab responses were investigated by miRNA qRT arrays to search for differentially-expressed miRNAs between three different breast cancer cell lines
When the Differentially Expressed (DE) miRNA lists for the two cell lines were intersected, 64 miRNAs were found to be commonly responsive to trastuzumab, of which 62 downregulated and 2 upregulated (Fig 1A)
Summary
Breast cancer is the most common malignancy in women, constituting approximately 30% of all cancer types [1]. Breast cancer is a heterogeneous disease with complex clinical behavior and responses to therapeutic intervention [2,3]. It is classified based on gene expression profiling, including HER2 positive (HER2+), luminal A or B, basal-like and presence of hormone receptors [4]. Tamoxifen citrate (TAM), which competes with the estrogen that binds to the estrogen receptor (ER), was the first selective estrogen receptor modulator (SERM) to be developed [6]. Tamoxifen has been used clinically for over 30 years as a partial agonist of ER to reduce the risk of recurrence and contralateral
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