新候选癌基因syncytin-1在膀胱癌中的分子机制及临床肿瘤学意义的研究

Bladder cancer is the most common malignancy of the urinary system. The carcinogenesis of bladder cancer is associated with environmental factors and genetic predisposition. Recent studies have been found that the overexpression of the human endogenous retrovirus (HERV) W family env (syncytin-1) can participate in a variety of malignant tumors. However, the molecular mechanism of syncytin-1 in the pathogenesis of bladder cancer is not clear. In the pre-experimental study, we found that overexpression of syncytin-1 gene was associated with bladder cancer, which may be serve as a potential indicator of bladder cancer. In the project, we are aimed to determine whether syncytin-1 overexpression in bladder cancer can be a novel target of bladder carcinogenesis by detecting the expression level of syncytin-1 gene in different tissues and urine exfoliated cells. Meanwhile, the transfection of fluorescent recombinant vectors and co-immunoprecipitation are used to detect the interaction between syncytin-1 and ASCT2 receptor in bladder cancer cells. In addition, with the RNA interference mediating the target siRNA to silence the expression of syncytin-1 or ASCT2, we detect the expression of cell growth factors in mTOR signal pathway. We will explore the molecular mechanisms of syncytin-1 involved in bladder cancer and finally confirm whether syncytin-1 as a human oncogene can be the new target for clinical therapy of bladder cancer.

膀胱癌是泌尿系统最常见的恶性肿瘤。膀胱癌的发病与环境、遗传等因素相关。最新研究发现人内源性逆转录病毒 (HERV) W家族 env (合胞素-1) 的异常表达参与多种恶性肿瘤的发生。本课题组在前期的预实验中发现合胞素-1的高表达与膀胱癌发生相关，但参与膀胱癌的发病机制还不明确。本项目旨在通过在不同良恶性组织和尿脱落细胞中检测合胞素-1的表达差异来明确其高表达能否成为膀胱癌预测的新靶标。另外通过荧光重组载体转染及免疫共沉淀技术分析合胞素-1与其受体ASCT2在膀胱癌细胞中的相互作用。通过结合干扰技术分别靶向性沉默合胞素-1和ASCT2的表达，检测细胞增殖情况及mTOR信号通路中多种细胞生长因子的表达差异，从分子及细胞水平探讨合胞素-1参与肿瘤发生的分子机制，最终明确合胞素-1是否能作为一个癌基因成为临床治疗膀胱肿瘤的新靶点。

膀胱癌复发率比较高，且复发与病程进展和不良预后密切相关，目前尚无有效的治疗手段。本项目从syncytin-1基因水平探讨膀胱癌发生的分子机制。收集临床样本120例，荧光定量RT-PCR与Western blot结果发现与非肿瘤样本和良性肿瘤组织样本相比，40例恶性肿瘤样本中有21例样本有syncytin-1的高表达，差异具有显著性。利用免疫组织化学染色（IHC），发现syncytin-1基因在肿瘤组织中高表达，并且m-TOR信号通路中蛋白（pmTOR, pERK, S6K1, ERK, p4EBP1等）也呈现高表达。通过荧光共聚焦及免疫共沉淀方法发现syncytin-1和ASCT2存在两个蛋白之间的相互作用，并发现两个蛋白定位在细胞膜上。在syncytin-1 高表达的实验中，流式细胞仪分析syncytin-1促进膀胱上皮细胞的增殖，而GPNA与雷帕霉素能抑制syncytin-1的增殖效应。Western blot结果发现syncytin-1高表达处理后p70S6K、S6K、p-ERK、p-mTOR、pAkT蛋白表达显著升高。经雷帕霉素处理后，p70S6K、S6K、p-ERK、p-mTOR、pAkT蛋白表达显著降低。Syncytin-1低表达后p70S6K、S6K、p4EBP1、p-ERK、p-mTOR、pAkT蛋白表达降低，经GPNA及雷帕霉素处理后，这些蛋白表达显著降低。因此，syncytin-1高表达可能作为一个潜在的预测膀胱癌的分子靶标通过激活mTOR信号通路从而参与膀胱肿瘤发生。