Metformin suppresses proliferation and invasion of drug-resistant breast cancer cells by activation of the Hippo pathway.

Jie Liu,Ruiqi Wang,Yi Miao,Pingping Li,He Chen,Juan Li,Peijun Liu

doi:10.1111/jcmm.15241

Abstract

Drug resistance limits the clinical efficacy of breast cancer therapies, and overexpression or activation of Yes‐associated protein (YAP) is common in drug‐resistant cancer cells. Thus, inhibition of YAP may reduce resistance to anti‐cancer drugs. Metformin (MET), a first‐line diabetes medication that also has anti‐tumour activities, induces AMP‐activated protein kinase (AMPK), directly phosphorylates YAP and inhibits YAP transcriptional activity. In this study, we determined the effect of MET on the proliferation and invasion of drug‐resistant breast cancer cells and then investigated the underlying molecular mechanism. Our in vivo and in vitro experiments indicated that MET suppressed breast cancer by an AMPK‐independent pathway to decrease YAP nuclear localization. In drug‐sensitive cells, MET activated the Hippo pathway by increasing KIBRA and FRMD6 expression, but this did not occur in drug‐resistant cells. Scribble (SCRIB), a cell polarity protein, was notably down‐regulated in tamoxifen‐ and paclitaxel‐resistant breast cancer cells relative to sensitive cells. We also found that MET suppressed the proliferation and invasion of drug‐resistant breast cancer cells by increasing the expression and cell membrane localization of SCRIB, which enhanced the interaction of SCRIB with MST1 and LATS1, and inhibited YAP nuclear localization and transcriptional activity.

Highlights

Breast cancer is the most common malignancy among women globally.[1]
Metastasis is often closely associated with the epithelial-mesenchymal transition (EMT),[20,21] a process in which multiple signalling factors induce the expression of specific transcription factors, such as SNAI1 and ZEB1.22 We found that MET treatment reduced the expression of these EMT markers in a concentration-dependent manner (Figure 3G)
Drug resistance is a major adverse effect that can occur during breast cancer therapy.[3,5]

Summary

| INTRODUCTION

Breast cancer is the most common malignancy among women globally.[1]. The most appropriate treatment depends on the breast cancer subtype and may include endocrine therapy (eg tamoxifen [TAM] and aromatase inhibitors), chemotherapy (eg paclitaxel [TAX] and docetaxel) and anti-HER2 agents (eg trastuzumab).[2]. Cells (BCSCs).[3,4,5,6] Recent studies have determined that YAP/TAZ overexpression and/or activation was a major reason for drug resistance in breast cancer.[7,8]. MET has AMPK-dependent and AMPK-independent effects.[12,13] Recent studies have examined the potential use of MET in cancer patients to decrease tumour growth, reduce the risk of cancer and improve prognosis.[14,15] The effect of MET on reducing the drug resistance of breast cancers is not clear. We examined the use of MET on the proliferation and invasion of breast cancer cells that were resistant to TAM or TAX by focusing on changes in the Scribble (SCRIB)-induced activation of the Hippo pathway. Monoclonal antibodies against p-AMPK, APMK, PCNA, cleaved caspase-3, caspase-3, KIBRA, FRMD6, Hippo pathway proteins and SCRIB were obtained from Cell Signaling Technology. The cells were fixed using 4% paraformaldehyde (PFA) and stained with 0.5% crystal violet

| MATERIALS AND METHODS

Findings

| DISCUSSION