Lu Jun-Yu, Jin Peng, Gao Wei, Wang De-Zhi, Sheng Jian-Qiu
Third Military Medical University, Chongqing, China, 400038.
Department of Gastroenterology, PLA Army General Hospital, Beijing, China, 100700.
Oncotarget. 2017 Jun 13;8(24):38767-38779. doi: 10.18632/oncotarget.16351.
Epidemiological data demonstrated that hormone replace treatment has protective effect against colorectal cancer (CRC). Our previous studies showed that this effect may be associated with DNA mismatch repair. This study aims to investigate the mechanism of estrogen induction of MLH1, and whether colorectal tumor proliferation can be inhibited through induction of MLH1 by estrogen signal pathway. Human CRC cell lines were used to examine the regulation of MLH1 expression by over-expression and depletion of estrogen receptor-α (ERα) and estrogen receptor-β (ERβ), under the treatment with 17β-estradiol or β-Estradiol 6-(O-carboxy-methyl)oxime:BSA, followed by a real-time Q-PCR and Western blotting analysis. Luciferase reporter and chromatin immunoprecipitation assays were used to identify the estrogen response elements in the proximal promoter of MLH1 gene. Then, the influence of estrogen-induced MLH1 on CRC tumor growth were determined in vitro and in vivo. We found that mismatch repair ability and microsatellite stability of cells were enhanced by estrogen via induction of MLH1 expression, which was mediated by ERβ, through a transcriptional activation process. Furthermore, we identified that ERβ exerted an inhibitory effect on CRC tumor proliferation in vitro and in vivo, combined with 5-FU, through up-regulation of MLH1 expression. Finally, we concluded that estrogen enhances mismatch repair ability and tumor inhibition effect in vitro and in vivo, via induction of MLH1 expression mediated by ERβ.
流行病学数据表明，激素替代治疗对结直肠癌（CRC）具有保护作用。我们之前的研究表明，这种作用可能与DNA错配修复有关。本研究旨在探讨雌激素诱导MLH1的机制，以及雌激素信号通路诱导MLH1是否能抑制结直肠肿瘤增殖。使用人CRC细胞系，在17β-雌二醇或β-雌二醇6-（O-羧甲基）肟：牛血清白蛋白处理下，通过过表达和敲低雌激素受体-α（ERα）和雌激素受体-β（ERβ）来检测MLH1表达的调节，随后进行实时定量PCR和蛋白质印迹分析。使用荧光素酶报告基因和染色质免疫沉淀试验来鉴定MLH1基因近端启动子中的雌激素反应元件。然后，在体外和体内确定雌激素诱导的MLH1对CRC肿瘤生长的影响。我们发现，雌激素通过诱导MLH1表达增强细胞的错配修复能力和微卫星稳定性，这是由ERβ介导的，通过转录激活过程实现。此外，我们发现ERβ通过上调MLH1表达，在体外和体内与5-氟尿嘧啶联合使用时，对CRC肿瘤增殖具有抑制作用。最后，我们得出结论，雌激素通过ERβ介导的MLH1表达诱导，在体外和体内增强错配修复能力和肿瘤抑制作用。
