肝癌发生男女性别差异的机制研究：Y染色体性别决定区域基因SRY的作用

The incidence of hepatocellular carcinoma (HCC) in men is 3 to 6 times higher than women worldwide. Thus, investigating the mechanism of gender disparity of HCC occurrence might be important to specific prevention and treatment of the disease. Previously, we untilized conditional hepatic β-catenin knockout mice model, in vitro gene knockdown model and human liver cancer specimen, and proved PDGFRα upregulation might be an "escape pathway" in β-catenin knockout or inhibited mice model or HCC cell lines in hepatocarcinogenesis. And, PDGFRα upregulation was predominantly identified in male.By screening, Sex-determining region on Y chromosome (SRY) was idenfied binding site in PDGFRα 3'-UTR. The prelimary data showed SRY was also significantly upregulated in tumor of β-catenin knockout male mice, which was consistent with PDGFRα upregulation. And inhibition of SRY by Dax-1 could significantly downregulate expression of PDGFRα. SRY was further identified overexpressed in around 85% male HCC. Since β-catenin was proved to bind with SRY directly and both of them could suppress each other. Therefore, we deduced that SRY might be an vital factor for enhancement of PDGFRα expression in context of β-catenin knockout or inhibition. And moreover, SRY might be an important motivator in hepatocarcinogenesis in male, which might account for gender disparity of HCC. In this project, 1)we would firstly construct liver-specific SRY transgenic mice model line. 2) By overexpression of SRY in male mice and ectopic expression of SRY in female mice, we explore the tumor incidence under DEN induction compared with their wildtype mice; 3) Together with in vitro studies, we further investigate the potential downstream effectors, such as PDGFRα, which SRY might modulate in hepatocarcinogenesis;4) Finally, we would try to test potential effects in inhibiting HCC initiation and development by targeting SRY or PDGFRα.

原发性肝癌男女发病率之比达到3-6:1。探讨肝癌发生性别差异的机制，对于肝癌针对性预防和治疗具有重要意义。前期我们应用基因敲除动物模型等，证实PDGFRα活化是β-catenin缺失或抑制条件下肝癌发生的重要原因；而PDGFRα活化在男性/雄性肝癌中占明显优势。通过筛选，我们发现PDGFRα3'-UTR存在Y染色体性别决定基因SRY结合位点。预实验证实，肝癌中SRY与PDGFRα表达水平一致；且抑制SRY可显著降低PDGFRα表达；SRY在约85%男性肝癌中高表达。由此推测：SRY可能是男性/雄性肝癌发生的重要机制之一，亦可能是肝癌发生性别差异的重要原因。本课题拟构建肝脏特异性SRY转基因小鼠模型，通过雄性小鼠过表达SRY及雌性小鼠获得性表达SRY，分别与野生鼠比较及性别间比较，肝癌发生率的差异；结合体外实验，探讨SRY通过PDGFRα等下游分子作用的机制及SRY作为靶点治疗肝癌的可行性。

肝癌发生存在显著性别差异， 男女总体发病率之比达到3-6:1 (GLOBOCAN 2008 (IARC).http://globocan.iarc.fr/factsheets/cancers/liver.asp )。男性肝癌发生率显著高于女性，且男性预后较女性更差。然而，肝癌发生性别差异的机制目前尚不得而知。既往关于雌激素和雄激素受体与肝癌相关研究和试验性治疗均未能获得预期结果。项目组国际首次发现Y染色体性别决定区域基因SRY可能促进男性和雄性动物肝癌发生。基于此前期研究结果和假说，项目组国际上首次构建肝脏特异性SRY转基因鼠模型，发现和证实：①： 83%的男性患者的肝癌组织中SRY过表达，女性正常肝组织不表达SRY；②：在化学致癌物诱导下，雄性小鼠过表达SRY后，肿瘤发生率、肿瘤直径等均高于野生鼠；③：雌性转基因小鼠获得性表达SRY后，肝癌发生率显著升高（与野生鼠比较）；④：在雄性和雌性转基因鼠模型中，我们均证实肝细胞中SRY过表达可促进其靶基因Sox9的表达以及下游PDGFRa信号通路活化，是转基因鼠肝癌发生的重要原因.⑤：SRY是促进肝癌发生的“癌基因”；亦可能是解释男性肝癌比女性高发的重要机制。.基于SRY在肝脏中的生理和病理意义尚未知的情况下，项目组结合临床现象，进一步应用转基因鼠模型，模拟临床疾病发生发展过程，探究两性在肝病发生和进展中的差异和可能的机制。初步证实SRY 是肝缺血再灌注损伤机制中新的效应分子，雄性小鼠肝缺血再灌注后SRY表达显著上调，并介导性别特异性肝缺血再灌注损伤；项目组进一步初步证实：β-catenin的抑制表达是SRY介导肝脏缺血再灌注损伤的重要下游分子；缺血再灌注过程中，NF-kB p65的活化表达可能是促进SRY活化表达的重要上游基因。.项目组拟进一步在转基因动物模型基础上深入探讨SRY在介导男性肝脏生理和病理过程中的作用和机制。