Department of Endocrine and Breast Surgery, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, P.R. China.
Key Laboratory of Laboratory Medical Diagnostics, Chinese Ministry of Education, Chongqing Medical University, Chongqing 400016, P.R. China.
Int J Oncol. 2017 Oct;51(4):1191-1198. doi: 10.3892/ijo.2017.4117. Epub 2017 Sep 5.
Tamoxifen resistance is a major clinical challenge in breast cancer treatment. Our previous studies find that GPER and its down-stream signaling play a pivotal role in the development of tamoxifen (TAM) resistance. cDNA array analysis indicated a set of genes associated with cell apoptosis are aberrant in GPER activated and TAM-resistant MCF-7R cells compared with TAM-sensitive MCF-7 cells. Among these genes, Bim (also named BCL2-L11), a member of the BH3-only pro-apoptotic protein family is significantly decreased, and TRIM RING finger protein TRIM2 (a ubiquitin ligase) is highly expressed in MCF-7R. To understand the mechanism of TAM-resistance in GPER activated ER+ breast cancer, the function of TRIM2 and Bim inducing cell apoptosis was studied. By using immunohistochemical and western blot analysis, there is an adverse correlation between TRIM2 and Bim in TAM-resistant breast tumor tissues and MCF-7R cells. Knockdown Bim in TAM-sensitive MCF-7 cells or overexpression of Bim in TAM-resistant MCF-7 cells significantly changed its sensibility to TAM through altering the levels of cleaved PARP and caspase-3. Activation of GPER and its downstream signaling MAPK/ERK, not PI3K/AKT, led to enhanced TRIM2 protein levels and affected the binding between TRIM2 and Bim which resulted in a reduced Bim in TAM-resistant breast cancer cells. Thus, the present study provides a novel insight to TAM-resistance in ER-positive breast cancer cells.
他莫昔芬耐药是乳腺癌治疗中的一个主要临床挑战。我们之前的研究发现，GPER 及其下游信号通路在他莫昔芬（TAM）耐药的发展中起着关键作用。cDNA 阵列分析表明，一组与细胞凋亡相关的基因在 GPER 激活和 TAM 耐药 MCF-7R 细胞中与 TAM 敏感 MCF-7 细胞相比存在异常。在这些基因中，Bim（也称为 BCL2-L11），BH3 仅凋亡蛋白家族的成员显著减少，而 MCF-7R 中 TRIM RING 指状蛋白 TRIM2（一种泛素连接酶）高度表达。为了了解 GPER 激活的 ER+乳腺癌中 TAM 耐药的机制，研究了 TRIM2 和 Bim 诱导细胞凋亡的功能。通过免疫组织化学和 Western blot 分析，在 TAM 耐药的乳腺癌组织和 MCF-7R 细胞中，TRIM2 和 Bim 之间存在负相关。在 TAM 敏感的 MCF-7 细胞中敲低 Bim 或在 TAM 耐药的 MCF-7 细胞中过表达 Bim，通过改变 cleaved PARP 和 caspase-3 的水平，显著改变了其对 TAM 的敏感性。GPER 的激活及其下游信号 MAPK/ERK，而不是 PI3K/AKT，导致 TRIM2 蛋白水平升高，并影响 TRIM2 和 Bim 之间的结合，从而导致 TAM 耐药乳腺癌细胞中 Bim 减少。因此，本研究为 ER 阳性乳腺癌细胞的 TAM 耐药提供了新的见解。
