HDAC3通过阻断易突变性DNA损伤修复抑制HCC发生发展的作用机制研究

Histone deacetylases (HDACs) are key proteins role in regulating DNA repair. The dysfunction of HDACs is closely related to tumorigenesis and cancer progression. HDAC inhibitor (HDACi) has already been used in cancer therapy. However, the mechanism of HDAC in liver cancer is not clear, and the therapeutic effect of HDACi on the treatment of liver cancer is limited. We found that HDAC3 expression is decreased in majority of human HCC cell lines and tumor tissues. Liver specific HDAC3 knockout (HDAC3LKO) mice got severe DNA damage in hepatocyte, and caused hepatocellular carcinoma. Functional studies revealed that gene silencing of HDAC3 significantly promoted HCC cell proliferation, invasion and metastases. Moreover, the downregulation of HDAC3 caused key enzymes that function in mutagenic DNA repair pathway upregulation. These results suggest that HDAC3 might play a role in tumor inhibition via blocking mutagenic DNA repair pathway. In this study, we plan to set up DNA injury models in HDAC3 overexpression or knockdown HCC cells to clarify the mechanism of HDAC3 in inhibiting mutagenic DNA repair pathway. We also plans to check the role of HDAC3 in HCC inhibition using HDAC3LKO mice. Our study may help us understanding the mechanism of tumor genesis, and clarifying the reasons for the limitation of HDACi in the treatment of liver cancer, and providing theoretical basis for clinical application of HDACi.

基因组不稳定性是恶性肿瘤的新特征，组蛋白去乙酰化酶（HDAC）在调控DNA损伤修复中发挥重要作用，其抑制剂（HDACi）已初显抗肿瘤前景。然而，HDAC在肝癌中的作用机制尚不明确，HDACi治疗肝癌的疗效非常有限。我们发现HDAC3在肝癌中低表达；肝脏特异敲除HDAC3（HDAC3LKO）小鼠的肝细胞DNA损伤严重并自发肝癌；沉默HDAC3后，肝癌细胞的增殖侵袭能力增强，易突变性DNA修复方式调控蛋白的表达上调，提示HDAC3可能通过阻断易突变性DNA修复发挥抑癌作用。本研究拟用HDAC3LKO小鼠和人肝癌细胞为实验对象，构建小鼠肝癌模型和沉默/过表达HDAC3细胞的DNA损伤模型，结合生物信息学数据分析，探讨HDAC3阻断易突变性DNA损伤修复，维持基因组稳定，进而抑制肝癌发生发展的分子机制。本研究将阐明HDACi治疗肝癌疗效局限的原因，丰富肝癌发生发展机制，为临床肝癌治疗提供理论依据。

基因组不稳定性是恶性肿瘤的新特征，组蛋白去乙酰化酶（HDAC）在调控DNA损伤修复中发挥重要作用，其抑制剂（HDACi）已初显抗肿瘤前景。然而，HDAC在肝癌中的作用机制尚不明确，HDACi治疗肝癌的疗效非常有限。我们前期研究发现HDAC3在肝癌中低表达；肝脏特异敲除HDAC3（HDAC3LKO）小鼠的肝细胞DNA损伤严重并自发肝癌；沉默HDAC3后，肝癌细胞的增殖侵袭能力增强，易突变性DNA修复方式调控蛋白的表达上调，提示HDAC3可能通过阻断易突变性DNA修复发挥抑癌作用。本研究期望通过构建小鼠肝癌模型和沉默/过表达HDAC3细胞的DNA损伤模型，结合生物信息学数据分析，探讨HDAC3阻断易突变性DNA损伤修复，维持基因组稳定，进而抑制肝癌发生发展的分子机制。本项目的研究开展过程中，我们通过HCC细胞HDAC3基因敲除实验进一步确认了HDAC3的抑癌基因特性，并使用HDAC3抑制剂联合DNA损伤做了治疗性研究。我们发现HDAC3缺失导致细胞pCHK2的表达上调和rH2AX染色增强，提示DNA损伤的存在；而DSB四条修复通路中的关键蛋白中PARP1和POLQ表达上调，提示激活了a-ej修复通路。通过进一步的机制解析，我们发现HDAC3通过抑制POLQ蛋白表达和翻译后修饰，调控DSB损伤后a-EJ修复通路，进而影响肝癌发生与发展的分子机制。通过本研究，我们解释了HDAC3抑制肝癌发生的分子机制，并证实HDAC3特异性抑制联合a-EJ修复通路抑制具有更好的抑制HCC的作用，为临床用药具有较好的指导意义。

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