Kim Jinkyoung, Lee Jiyun, Kim Chungyeul, Choi Jinhyuk, Kim Aeree
Department of Pathology, Korea University Guro Hospital, #148 Gurodong-ro, Guro-gu, Seoul, 152-703, Korea.
Department of Pathology, College of Medicine, Korea University, #73 Inchon-ro, Seongbuk-gu, Seoul, 136-705, Korea.
Tumour Biol. 2016 May;37(5):5811-9. doi: 10.1007/s13277-015-4440-9. Epub 2015 Nov 18.
Development of new therapeutic strategies is becoming increasingly important to overcome tamoxifen resistance. Recently, much interest has been focused on anti-tumor effects of metformin commonly used to treat type II diabetes. Increased protein expression and signaling of epidermal growth factor receptor (EGFR) family is a possible mechanism involved in tamoxifen resistance. Since HER2/HER3 heterodimers are able to induce strong downstream signaling and activate various biological responses such as cellular proliferation and growth, we investigated the anti-cancer effect of metformin by inhibition of signaling pathway via downregulation of HER2 and HER3 using tamoxifen-resistant MCF-7 (TR MCF-7) cells. Compared to MCF-7 cells, TR MCF-7 cells showed increased expression of EGFR, HER2, and HER3, and metformin inhibited the expression of these proteins in a dose- and time-dependent manner. Metformin inhibited activation of HER2 (Tyr1248)/HER3 (Tyr1289)/Akt (Ser473) as well as cell proliferation and colony formation by estrogenic promotion in MCF-7 and TR MCF-7 cells. Known as a HER3 ligand, heregulin (HRG)-β1-induced phosphorylation of HER2, HER3 and Akt, and protein interaction of HER2/HER3 and colony formation were inhibited by metformin in both cells. Consistent with the results in the two cell lines, we identified that metformin inhibited HER2/HER3/Akt signaling axis activated by HRG-β1 using the HER2 and HER3-overexpressing breast cancer cell line SK-BR-3. Lastly, lapatinib-induced HER3 upregulation was significantly inhibited by treatment of metformin in HER3 siRNA-transfected TR MCF-7 cells. These data suggest that metformin might overcome tamoxifen resistance through the inhibition of expression and signaling of receptor tyrosine kinase HER2 and HER3.
开发新的治疗策略对于克服他莫昔芬耐药性变得越来越重要。最近，人们对常用于治疗II型糖尿病的二甲双胍的抗肿瘤作用给予了极大关注。表皮生长因子受体（EGFR）家族蛋白表达和信号传导增加是他莫昔芬耐药的一种可能机制。由于HER2/HER3异二聚体能够诱导强烈的下游信号传导并激活各种生物学反应，如细胞增殖和生长，我们使用对他莫昔芬耐药的MCF-7（TR MCF-7）细胞，通过下调HER2和HER3来抑制信号通路，研究了二甲双胍的抗癌作用。与MCF-7细胞相比，TR MCF-7细胞中EGFR、HER2和HER3的表达增加，二甲双胍以剂量和时间依赖性方式抑制这些蛋白的表达。二甲双胍抑制MCF-7和TR MCF-7细胞中HER2（Tyr1248）/HER3（Tyr1289）/Akt（Ser473）的激活以及雌激素促进的细胞增殖和集落形成。作为HER3配体的这里格蛋白（HRG）-β1诱导的HER2、HER3和Akt磷酸化以及HER2/HER3的蛋白相互作用和集落形成在两种细胞中均被二甲双胍抑制。与这两种细胞系的结果一致，我们使用过表达HER2和HER3的乳腺癌细胞系SK-BR-3确定二甲双胍抑制了HRG-β1激活的HER2/HER3/Akt信号轴。最后，在HER3 siRNA转染的TR MCF-7细胞中，二甲双胍处理显著抑制了拉帕替尼诱导的HER3上调。这些数据表明，二甲双胍可能通过抑制受体酪氨酸激酶HER2和HER3的表达及信号传导来克服他莫昔芬耐药性。
