砷调控膀胱上皮细胞HER2过表达的分子机制及其在下游肿瘤相关信号通路中的作用研究

Arsenic is a poisonous metalloid distributed in the worldwide environment and induced multi-system diseases, including diabetes, hypertension, and hyperkeratosis, especially increased risks of skin cancer and internal cancers of bladder, liver and lung cancers, and has been as Group 1 human carcinogen by IARC. The proposed molecular mechanisms of arsenic-induced carcinogenesis are mainly epigenetic mechanisms, leading to the activation of proliferative and carcinogenic signaling pathways. ..Our previous studies found that MAPK、PI3K/AKT and JAK2/STAT3 pathways were activated in arsenic treated human uroepithelial cells line (SV-HUC-1), which increased expressions of Cyclin D1、PCNA、VEGF、HIF-1α. Some studies reported that the upstream of MAPK、PI3K/AKT and JAK2/STAT3 pathways is HER2, a member of the erythoblastosis oncogene B (ErbB) receptor tyrosine kinase (RTK) family. Our studies showed that mRNA and protein expressions of HER2 were increased in arsenic treated SV-HUC-1 cells. Therefore, we presume that HER2 phosphorylation induced by arsenic could increase the activation of downstream pathways, such as MAPK、PI3K/AKT and JAK2/STAT3, which promote cell survival, proliferation, angiogenesis and invasion in arsenic treated uroepithelial cells...In this study, HER2 and its regulated proteins including HSP90 (a chaperone), NDRG1 (N-myc downstream-regulated gene 1) and HER family ligands (EGF, TGFα, s-Ecad) will be studied in arsenic-treated SV-HUC-1 cells and rats exposed to arsenic, in order to understand the molecular mechanism of HER2 overexpression. The effects of HER2 on MAPK、PI3K/AKT and JAK2/STAT3 pathways also will be studied to explore the intervention target of bladder damage induced by arsenic. In addition, the persons lived in areas of presence of arsenic in drinking will be investigated to analysis the relationship between urinary arsnic concentrations and HER2 expressions, levels of EGF, TGFα and s-Ecad. The systemic studies will not only help to reveal the molecular mechanism of bladder cancer induced by arsenic, but also provide a feasible project for bladder cancer prevention and treatment in arsenic exposure population.

砷是国际癌症研究属确定的人类致癌物，可引起膀胱癌。我们先前研究发现砷能够激活人膀胱上皮细胞MAPK、PI3K/AKT、JAK2/STAT3信号通路，文献显示这三条信号通路的上游均可被原癌基因HER2所调控。我们前期实验证明砷能够诱导人膀胱上皮细胞HER2表达增高，因此，本研究以HER2为切入点，从体外细胞实验和大鼠体内动物实验，研究HER家族配体、分子伴侣蛋白HPS90和生长转移抑制因子NDRG1调控砷致膀胱上皮细胞HER2活化和稳定性的分子机制，以及HER2对其下游肿瘤发生相关信号通路激活的作用，探索砷致膀胱癌的机制及其干预靶点。并通过开展高砷暴露人群现场调查，分析尿中砷化物浓度与HER2表达及其配体分泌水平的相关关系，筛选砷对膀胱上皮损伤的早期生物标志物，为高砷暴露人群膀胱癌的预防、治疗提供可行的方案和措施。

砷是国际癌症研究属确定的人类致癌物，可引起皮肤癌、肺癌和膀胱癌。全球约有70个国家1亿4千万人处于饮水砷暴露的风险中。我国除了有色金属冶炼、砷矿开采等职业砷暴露外，12个省有饮水型或燃煤型地方性砷中毒病区，砷中毒病人已达3万。我们研究组体外细胞实验已观察到长期低浓度亚砷酸钠处理的人正常膀胱上皮细胞增殖速度明显加快，出现恶性转化倾向。因此，探索砷致膀胱癌机制，寻找有效的预防控制措施和治疗方案尤为重要。本研究以砷增加癌基因HER2过度活化为切入点，研究砷处理的膀胱上皮细胞、砷暴露的大鼠膀胱和砷暴露人群尿中HER2配体EGF、TGFα、s-Ecad表达和分泌情况，以及这些配体对砷处理条件下增加HER2同源或异源二聚体形成、促进其磷酸化的调控作用；研究活化的HER2对其下游肿瘤相关信号通路的影响及其促进膀胱上皮细胞过度增殖和恶性转化情况；研究HER2调控IL-8在砷致SV-HUC-1细胞迁移中的作用及机制。研究发现，短期和长期砷处理能够促进人正常膀胱上皮细胞HER2磷酸化，及其配体EGF、TGFα和sE-cad的蛋白水平升高；高砷暴露人群尿中HER2配体sEcad和EGF水平升高，与尿中砷化物呈正相关关系。EGF、TGFα作为EGFR的配体，可通过促进HER2与EGFR的异源二聚化，进而导致HER2磷酸化，引起细胞增殖迁移能力增强。砷处理能够上调HSP90的蛋白表达，下调HER2抑制蛋白IL-6和NDRG1蛋白水平，使磷酸化的HER2不易被降解。砷处理能够诱导SV-HUC-1细胞恶性转化，形成HER2-Src复合物，进而诱导Raf1/ERK1/2、PI3K/AKT和STAT3信号通路活化，导致细胞PCNA、Cyclin D1和VEGF、HIF-1α的水平升高，参与砷诱导SV-HUC-1细胞恶性转化过程。通过建立DMAⅤ暴露和HER2抑制剂干预的大鼠动物模型，得到与体外细胞实验一致的结果。此外，发现长期砷处理能够诱导SV-HUC-1细胞发生EMT并促进细胞迁移，引起炎性细胞因子IL-8表达和分泌增加；HER2通过MAPK、JNK、PI3K/AKT和GSK3β信号通路的激活上调IL-8表达和分泌；IL-8可触发ERK、PI3K/AKT和STAT3途径，从而导致EMT和迁移。本研究探索了砷致膀胱癌的机制及其干预靶点，为砷致膀胱癌的预防和控制提供科学依据。