NAT10调节微核形成及相关结直肠癌生物学活性作用与机制研究

Micronuclei is generally detected in most of cancer cells. SASP (Senescence associated secretory phenotype) is a cell senescence-associated regulatory machinery under extensively investigation in current. Through either autocrine or paracrine way, SASP could induce cell senescence and promotes production of pro-inflammatory factors, which prove subsequently causing genomic instability of cancer cells and remodeling of tumor microenvironment, resulting in tumor progression. It has been recently demonstrated that SASP could be triggered by the binding of cGAS(cyclic GMP-AMP synthase) to free DNA in cytosol with resultant production of the second messenger 2,3-cyclic GMP-AMP, which activates STING(Stimulator interferon of gene) and its downstream genes. Nucleophagy formed from micronuclei of cancer cells is considered to be the main source of cytoplasmic DNA. Therefore, elucidation of SASP activation by micronuclei and related nucleophagy in cancer cells could be important to cancer development and therapeutic treatment. N-acetyltransferase 10(NAT10) has been identified to regulate the activities of cellular nucleolus, cytokinesis and cytoskeleton remodeling. We have also revealed that NAT10 could regulate biological activities of colorectal cancers, and beyond, recently we have discovered that NAT10 does usually localize in micronuclei in most of cancer cells, and subsequently co-localizes with the key factors responsible for autophagy such as LC3, SQSTM1, LAMP2 to form nucleophagy, and probably also interacts with cGAS. The treatment of Remodelin, a NAT10 inhibitor, or genomic deletion of NAT10 by CRISPR/Cas9 could reduce markedly the formation of NAT10 micronuclei, nucleophagy and interaction with cGAS, indicating that NAT10 could be involved in regulation of micronuclei, nucleophagy and SASP activation. Thus, the proposal is to plane to get insight of the molecular mechanism about the involvement of NAT10 in the formation of micronuclei and nucleophagy as well as SASP activation, and then to clarify NAT10-related SASP on the regulation of biological activity of colorectal cancers, and further to explore the applicable potentials in clinic treatment of colorectal cancers.

微核普遍存在于肿瘤细胞。衰老分泌表型(SASP)是近年来发现的与细胞衰老相关的重要调节机制，可以诱导癌细胞基因组不稳定及肿瘤微环境改变而促进肿瘤恶性表型。SASP活化主要由cGAS结合胞浆游离DNA而触发，而微核及相关自噬可能是癌细胞激活SASP的主要途径。乙酰化酶NAT10具有调节细胞核仁、分裂、细胞骨架等多种功能。我们已经证明NAT10与结直肠癌生物学特性具有重要关系，同时在新近研究中又发现NAT10普遍存在于癌细胞微核、与自噬相关蛋白形成核自噬体而激活cGAS，而NAT10抑制剂Remodelin或基因敲除均可降低癌细胞微核、核自噬、及cGAS活化，提示NAT10与SASP调节机制具有重要联系。因此，拟以结直肠癌为对象进一步阐明NAT10对微核、核自噬、SASP的调节作用和机制，确定NAT10微核激活SASP机制对结直肠癌生物学特性的调节作用，并探讨其在结肠癌临床治疗中的应用。

研究聚焦NAT10表达及活性、 微核形成、 cGAS-STIN介导的衰老相关分泌表型（SASP）与DNA自噬作用之间的关系，以及在调节癌细胞生存、演进中的作用。 研究表明：1）NAT10常为癌细胞微核的组份，与rDNA重复序列相关，表明复制应激与微核形成的关系，同时，NAT10通过促进DNA复制而增强复制应激，调节细胞微核形成，微核DNA损伤可直接激活胞浆cGAS而诱导SASP作用，以自分泌或旁分泌形成促进癌细胞演进；2）NAT10参与DNA复制起始的调节，可能通过与CDC6相互作用参与DNA复制起点的形成作用，基因敲除或化学抑制NAT10均能显著抑制DNA复制、复制应激以及相关微核形成。3）本研究同时发现，具有高度微核形成癌细胞其具有很高的DNA自噬活性，为游离胞浆基因组DNA通过激活cGAS-STING介导的DNA自噬作用，这种作用对于维持癌细胞生存具有重要的意义，抑制DNA自噬可为抗肿瘤治疗策略。因此，研究证明了DNA复制应激、微核形成，并分别通过激活cGAS-STING介导的SASP作用，或DNA自噬作用，促进癌细胞的生存与演进。这种选择性与癌细胞DNA复制应激、损伤程度有关；4）癌细胞核纤层蛋白LMNB1基因突变可能诱导高度的细胞微核形成，从而激活cGAS-STING介导的DNA自噬作用； 5）在胃癌发生中，胃癌细胞增殖、DNA复制、DNA损伤应激与SASP激活以及p53基因突变具有密切的关系；6）NAT10表达或活性在HIF表达中具有重要作用，降低NAT10活性可抑制调节及结构性HIF表达；7）抑制NAT10可作为抗肿瘤靶点：抑制NAT10可降低DNA复制应激，抑制微核形成或癌细胞增殖。.研究的创新点：.1）微核形成中DNA复制应激的重要作用；2）微核激活cGAS-STING介导SASP与DNA自噬的选择性，以及对癌细胞生物学活性调节的分别意义，抑制DNA自噬可为抗肿瘤治疗策略；3）微核激活cGAS无需核自噬，而主要与DNA损伤有关，DNA自噬可由cGAS-STING介导，与大分子自噬相一致；4）核纤层蛋白异常可能导致DNA损伤，而诱导基因组DNA胞浆释放而诱导DNA自噬作用；5）NAT10表达或活性在HIF表达中具有重要作用；6）NAT10可作为抗肿瘤靶点。