乳腺发育关键期砷暴露对远期乳腺癌易感性的影响及机制研究

Arsenic is a human carcinogen and also recognized as a potential endocrine disruptor. Although some studies have shown that arsenic exposure is associated with the risk of breast cancer, the relationship still need to be further confirmed. The period of embryo and puberty are the key stages of mammary gland development, and exposure to harmful factors at the two stages may increase the risk of breast cancer. p62 is a multi-functional protein and is associated with the occurrence and prognosis of various types of cancer, including breast cancer. Long-term arsenic exposure induces increased p62 levels. Therefore, we propose that arsenic exposure at the key stages of mammary gland development increases the risk of breast cancer and the effect is probably related to arsenic-induced accumulation of p62 and p62-related cancer signaling pathways. In this project, we will use animal experiment to explore the influence of arsenic exposure at embryo and embryo plus puberty on the long-term breast cancer susceptibility. Meanwhile, we will use lentivirus-mediated short hair RNA stable knockdown of p62 to identify the role of p62 in arsenic-induced increased breast cancer susceptibility and malignant transformation of human mammary epithelial cell. The p62-related cancer signaling pathway nuclear factor E2-related factor-2 (Nrf2) and mammalian target of rapamycin complex 1 (mTORC1) are used as key points to illustrate the modulatory mechanism of p62 on arsenic-induced carcinogenic effects. This project will help to elucidate the relationship of arsenic and breast cancer and also shed new light on the carcinogenic mechanism of arsenic.

砷是人类致癌物，也是潜在内分泌干扰物。有研究提示，砷暴露与乳腺癌发病风险有关，但仍需进一步证实。胚胎期和青春期是乳腺发育的关键期，这一时期有害因素暴露会增加乳腺癌易感性。p62是一种多功能蛋白，能够影响多种癌症（包括乳腺癌）发生与预后。长期砷暴露可导致p62蓄积。由此我们假设：乳腺发育关键期砷暴露增强远期乳腺癌易感性，该效应可能与砷诱导的p62蓄积及其调控的癌症通路活化密切相关。本项目拟通过动物实验探讨小鼠胚胎期和胚胎期叠加青春期砷暴露对远期乳腺癌易感性的影响；同时联合慢病毒稳转沉默p62的乳腺上皮细胞实验，阐明p62在砷致乳腺癌易感性增高或细胞恶性转化中的作用；以p62相关癌症信号通路核因子E2相关因子2（Nrf2）及雷帕霉素靶蛋白复合体1（mTORC1）为切入点，解析p62发挥上述作用的具体机制。本项目将有助于阐明砷与乳腺癌之间的关系，且为砷致癌机制研究提供新思路。

砷是国际癌症中心确认的I类致癌物。乳腺癌与砷暴露的关系在近些年来逐渐被揭示，但仍然需要进一步证实。乳腺癌的发生与生命早期乳腺发育异常密切相关。本项目利用体内动物实验证实胚胎期饮水型砷暴露能够促进雌性仔鼠乳腺组织终末乳芽（TEB）的形成以及乳腺导管在脂肪垫上的浸润，增加TEB内细胞增殖相关抗原Ki67的表达，提示砷暴露能够导致乳腺发育异常，该研究结果同时揭示无机砷暴露可能会增加乳腺癌的易感性。另一方面，本项目利用体外细胞实验证实长期环境相关水平无机砷暴露能够诱导人正常乳腺上皮细胞（MCF-10A）发生恶性转化。p62蛋白在恶性转化细胞中过度表达。雷帕霉素靶蛋白复合体1（mTORC1）相关分子（p-mTOR，p-P70S6K，p-4EBP1）在砷暴露诱导恶性转化的过程中被活化。利用慢病毒稳转沉默p62可显著抑制砷诱导的恶性转化，且在这一过程中mTORC1信号通路相关分子（p-mTOR，p-P70S6K，p-4EBP1）的表达也被显著抑制。同时，核因子E2相关因子2（NRF2）信号通路相关分子（NQO1，GCLM）在恶性转化细胞中显著上调，且可被p62沉默所抑制。除此之外，我们还发现G蛋白偶联雌激素受体（GPER）在砷恶转细胞中过度表达，GPER/EGFR/ERK信号通路在砷恶转过程中被逐渐激活。本项目结果为探讨砷与乳腺癌的关系提供了直接证据，并从新的角度解析了砷致乳腺癌的机制，为砷性癌症的防治提供了理论基础。