SENP2介导的乳酸脱氢酶A去SUMO化修饰抑制乳腺癌增殖与转移的机理研究

Breast cancer seriously endangers the health of women, and it is urgent to study its pathogenesis and find new potential anti-cancer targets. A large number of studies have shown that lactate dehydrogenase LDHA is highly expressed and overactive in most tumor tissues, and inactivation of LDHA can significantly inhibit the occurrence and development of tumor. SUMOylation is an important protein post-translational modification and de-SUMOylation mediated by the SUMO-specific proteases (SENPs) is the key factor that determines the modification level and function of target protein. We previously confirmed the SUMOylation of endogenous LDHA in breast cancer cells, and data from in vitro enzymatic activity test showed that SUMOylation-deficiency significantly inhibited LDHA activity. In addition, LDHA was identified as a potential substrate for SENP2 by mass spectrometry analysis, and SENP2 could readily remove the SUMO modification of LDHA in vivo, suggesting that SENP2-mediated de-SUMOylation of LDHA might be involved in the regulation of the occurrence and development of breast cancer. To test this hypothesis, we plan to carry out intensive studies to clarify the regulatory role of SUMOylation in LDHA enzymatic activity, and elucidate the mechanism and clinical significance of SENP2-mediated de-SUMOylation of LDHA in inhibiting proliferation and metastasis of breast cancer. Our research will provide a scientific basis for the identification of molecular targets for anti-breast cancer.

乳腺癌严重危害女性健康，迫切需要深入研究其发病机理并寻找新的潜在抗癌靶点。研究表明乳酸脱氢酶LDHA在多数肿瘤组织中高表达并过度活化，且灭活LDHA可显著抑制肿瘤的发生发展。SUMO化修饰是一种重要的蛋白翻译后修饰方式，由SUMO特异性蛋白酶SENPs介导的去SUMO化修饰则是决定靶蛋白SUMO化修饰水平和功能的关键因素。在乳腺癌细胞中我们证实内源性LDHA可发生SUMO化修饰，且体外酶活测试显示SUMO化修饰缺失抑制LDHA酶活。而且，质谱分析LDHA为SENP2的潜在底物，SENP2在体内能显著去除LDHA的SUMO化修饰，提示SENP2介导的LDHA去SUMO化修饰可能参与对乳腺癌发生发展的调控。本项目旨在检验该假说，明确SUMO化修饰对LDHA酶活的调节作用，揭示SENP2介导的LDHA去SUMO化修饰抑制乳腺癌增殖与转移的机理及临床意义，为抗乳腺癌分子靶点的鉴定提供重要科学依据。

本项目拟研究SUMO化修饰对乳酸脱氢酶LDHA活性的调节作用，并揭示去SUMO化酶SENP2负调控LDHA酶活和乳腺癌细胞生物学功能的作用机理以及SENP2抑制乳腺癌增殖与转移的生理病理意义。通过研究，我们发现LDHA为新鉴定的SUMO化修饰底物，且Lys-14为LDHA主要的SUMO化修饰位点，该位点突变之后可显著抑制LDHA的酶活。我们进一步证实了去SUMO化酶SENP2在乳腺癌组织中较正常组织呈特异性低表达，且SENP2可结合LDHA并介导其去SUMO化修饰。相反，LDHA的催化产物乳酸可明显抑制SENP2的转录表达，提示乳腺癌细胞中SENP2通过去SUMO化负调控LDHA酶活的反馈调节机制。此外，我们还发现磷脂酰激酶PIPKIγ可与SUMO特异性结合酶UBC9相互作用并发生SUMO化修饰，Lys-591为其主要的SUMO化修饰位点。并进一步揭示SUMO化修饰是PIPKIγ驱动角质形成细胞迁移与生长必要条件，若SUMO化修饰缺失则会显著扰乱细胞内由PIPKIγ所催化的PIP2生成。该研究证实了PIPKIγ为一个新的SUMO化修饰靶点，并阐明了PIPKIγ的SUMO化修饰调控角质形成细胞功能的重要作用，为深入研究创伤修复提供了重要方向（FEBS Journal, 2019 Dec; 286(23): 4709-4720）。另外，我们还发现SUMO特异性蛋白酶家族的另一重要成员SENP1在儿童急性淋巴细胞白血病（ALL）复发样本中呈特异性高表达，并首次证实去SUMO化酶SENP1在ALL细胞中的生物学功能，即SENP1表达沉默在不显著改变ALL细胞对临床常用化疗药物敏感性的情况下，会加速ALL细胞凋亡继而抑制其恶性增殖。机制上，SENP1可特异性介导DNA拓扑异构酶Ⅰ (TOP1) 的去SUMO化修饰从而稳定TOP1蛋白，继而减弱TOP1抑制剂7-乙基-喜树碱（7E-CPT）与拓扑替康（TPT）对TOP1的靶向抑制作用以及对ALL细胞的促凋亡效应，从而介导TOP1抑制剂7E-CPT/TPT的抗白血病作用（Biochim Biophys Acta Mol Basis Dis. 2022 Dec 1; 1868(12):166492）。