miR-375 targeting YAP1 modulates trastuzumab resistance through epithelial-mesenchymal transition in breast cancer cells

Background and purpose: As the targeted antibody of human epidermal growth factor receptor 2 (HER2), trastuzumab resistance gets more and more attention. This study aimed to explore the role of miR-375 in the occurrence of trastuzumab resistance in breast cancer cells through regulating epithelial-mesenchymal transition (EMT) by targeting Yes-associated protein 1 (YAP1). Methods: Trastuzumab-resistant breast cancer cell line was established. miR-375 mimic and recombinant plasmid YAP1 were transfected into SK-BR-3R cells. The sensitivities of each breast cancer cell line to trastuzumab were detected by MTT assay, and proliferation was detected by colony formation assay. Real-time fluorescence quantitative polymerase chain reaction (RTFQ-PCR) and Western blot were applied to detect mRNA and protein expressions of miR-375, vimentin, E-cadherin and YAP1. Dual-luciferase reporter gene assay was conducted to verify the role of miR-375 in regulation of YAP1 transcription. A total of 25 breast cancer tissues from patients were collected to detect correlation in clinical performance. Results: Compared with NC group, after transfection with miR-375 mimic, the sensitivity to trastuzumab (P