LATS1的乙酰化修饰调控YAP在胰腺癌转移中的作用及分子机制研究

Pancreatic cancer remains the most lethal human malignancy, with a 5 year survival rate of less than 5%. YAP, the effector of Hippo pathway, is essential for the initiation of pancreatic cancer, but little is known about the mechanism of YAP in pancreatic cancer metastasis. LATS1 is a upstream kinase of YAP, which inhibites YAP by phosphorylating on multiple sites. In our previous study, we found that YAP is significantly activated in metastatic pancreatic cancer and active YAP promotes the invasion and migration of pancreatic cancer cells. In addition, we also found that LATS1 is acetylated at K998, and LATS1 acetylation enhances its inhibition on YAP. HDAC6 was the deacetylase of LATS1, which was highly expressed in pancreatic cancer. Since protein acetylation is a reversible process, we speculate that there should be some kind of acetyltransferase in pancreatic cancer cells, which regulates LATS1 acetylation together with HDAC6 and promotes pancreatic cancer metastasis by activating YAP. In this study, we will clarify the molecular mechanism of LATS1 acetylation and explore its role in pancreatic cancer metastasis. Our study will lay a foundation for revealing the pathogenesis of pancreatic cancer metastasis and provide a potential target for pancreatic cancer treatment.

胰腺癌是最致命的恶性肿瘤之一，五年生存率不足5%。Hippo-YAP通路在胰腺癌发生中具有至关重要的作用，但其在胰腺癌转移中的作用机制尚不完全清楚。我们前期研究发现YAP在转移性胰腺癌中显著激活，且激活的YAP能促进胰腺癌细胞的侵袭迁移能力。LATS1是YAP上游激酶，前期实验发现LATS1的K998位点存在乙酰化修饰，且该位点的乙酰化促进LATS1对YAP的磷酸化抑制。此外，我们还发现HDAC6能调节LATS1的去乙酰化，且在胰腺癌中高表达。鉴于蛋白乙酰化修饰是可逆的，我们推测，细胞中还存在某种乙酰转移酶与HDAC6一起共同调控LATS1的乙酰化水平，进而激活YAP并促进胰腺癌转移。本课题拟在前期工作基础上，以LATS1乙酰化为切入点，进一步阐明LATS1发生乙酰化的分子机制，以及LATS1的乙酰化修饰调控YAP在胰腺癌转移中的作用机制，以期为胰腺癌治疗提供潜在靶点和理论依据。

胰腺癌是人类最致命的恶性肿瘤之一，易转移，预后极差。对于转移性胰腺癌目前尚无有效的治疗策略。YAP是Hippo信号通路的主要效应因子,作为转录共激活因子调控下游基因的表达，与肿瘤发生发展密切相关。激酶级联反应是Hippo通路的核心，除了磷酸化以外，是否还有别的蛋白翻译后形式参与YAP的调控？我们的研究发现LATS1的K998位点存在乙酰化修饰，乙酰转移酶p300与去乙酰化酶HDAC6共同调控LATS1的乙酰化水平。LATS1乙酰化促进其对YAP S127位点的磷酸化，阻断YAP入核发挥转录调节功能。将K998位点突变为R，使其不能发生乙酰化，减弱了LATS1对YAP的磷酸化抑制，将K998位点突变为D，模拟该位点的乙酰化状态，则促进LATS1对YAP的磷酸化抑制。我们前期研究发现YAP在转移性胰腺癌中显著激活，且激活的YAP能促进胰腺癌细胞的侵袭迁移能力。细胞及动物实验进一步研究证实，LATS1乙酰化通过促进YAP磷酸化抑制胰腺癌转移，且LATS1乙酰化低表达与胰腺癌患者不良预后相关。此外，我们还研究了YAP与自噬的相互调控在胰腺癌中的作用机制，发现YAP在胰腺癌中高表达，并通过促进Atg5转录激活自噬，而自噬又可以将YAP降解，形成反馈调节环路。而胰腺癌中YAP的过度活化使得YAP-自噬环路失衡，并促进肿瘤进展。抑制自噬能增强YAP在胰腺癌中的致癌活性。此外，我们还发现YAP通过上调survivin转录促进肝癌细胞索拉菲尼耐药，YAP抑制剂Verteporfin可显著增强索拉菲尼的抗肿瘤活性。通过该项目的实施，拓展了我们对Hippo-YAP信号通路在胰腺癌中的认识，并为靶向YAP的胰腺癌治疗提供了理论依据。