LATS2低表达活化Wnt/β-catenin信号通路在慢性淋巴细胞白血病耐药中的机制研究

Chronic lymphocytic leukemia (CLL) is still a incurable disease with heterogeneous course and always resistant to chemotherapy at advance or relapsed stage. Our previous study had proved that tumor suppressed gene LATS2 was down-regulated in CLL, especially in the relapsed or resistant patients. Low expression of LATS2 is a new poor prognostic factor of CLL. Knock-down of LATS2 by siRNA in HeLa cell made the Wnt/β-catenin signaling pathway constitutively activated and reduce the sensitivity of HeLa cell to chemotherapeutic drug. Wnt/β-catenin signaling pathway is known to play important role in drug-resistance in many cancer, and is constitutively actived in CLL. In this project, we will further investigate ① whether the low expression of LATS2 will make the constitutive activation of Wnt/β-catenin signaling pathway in CLL. ② Whether the low expression of LATS2 or the constitutive activation of Wnt/β-catenin signaling pathway will cause the drug resistance of CLL. ③ Whether low expression of LATS2 will cause the drug resistance through constitutively activating the Wnt/β-catenin signaling pathway in CLL. ④ We will identify the above outcomes in NOD/SCID mouse model and in the primary CLL cells. This project will elucidate the mechanism of down-regulated LATS2 in the of drug resistance of CLL, and provide the evidence to explore LATS2 as a valuable therapeutic target for the treatment of CLL. So this project has great academic and applicative value.

慢性淋巴细胞白血病（CLL）是一种异质性很强的不可治愈性肿瘤，晚期或复发后多耐药。我们前期研究证明抑癌基因LATS2在CLL中显著低表达，复发耐药患者更为明显，是CLL新的不良预后因素；功能研究初步显示LATS2低表达可导致Wnt/β-catenin信号通路活化，并可导致肿瘤细胞耐药。已知Wnt/β-catenin通路在CLL中持续活化，是多种肿瘤耐药的主要原因。本课题拟进一步探讨①CLL中LATS2低表达是否导致Wnt/β-catenin通路持续活化；②CLL中LATS2低表达或Wnt/β-catenin通路持续活化是否导致CLL耐药；③LATS2是否通过Wnt/β-catenin通路导致CLL耐药；④小鼠体内及CLL患者原代标本中验证相关结果。本课题研究结果将揭示LATS2在CLL中的具体作用机制以及CLL的耐药原因，为研究CLL的治疗提供一个新靶标，具有重要的理论意义和实用价值。

B细胞非霍奇金淋巴瘤（B-NHL）是血液系统常见的恶性肿瘤，患者生存差异大，晚期或复发后患者多耐药。复发耐药患者多数尚缺乏有效的治疗选择，生存极差。目前耐药机制尚不十分明确，有研究显示致病相关信号通路异常活化或者染色体不稳定相关可能与耐药相关。Hippo信号通路是调节实体肿瘤细胞增殖、迁移及维持细胞干性关键的信号通路。但是Hippo信号通路与血液系统肿瘤，尤其是B-NHL的关系尚不明确。我们研究发现Hippo信号通路的核心分子LATS2在CLL患者中显著低表达，复发耐药患者更为明显，是CLL新的不良预后因素。而LATS2的低表达可降低其对下游分子YAP的磷酸化抑制作用，导致YAP表达升高，从而与TEAD结合进入细胞核发挥转入调节作用，致使细胞增殖。在B-NHL患者中，我们检测了YAP表达的表达，发现在B-NHL患者中YAP表达明显高于正常供者B细胞，且复发难治患者表达更高。使用shRNA敲除YAP或者YAP抑制剂维替泊芬（VP）处理可导致套细胞淋巴瘤（MCL）细胞系Z138及Granta519细胞增殖减慢，凋亡加快，细胞发生G1期阻滞。干扰YAP可增加BTK抑制剂ibrutinib及syk抑制剂R788药物敏感性，增加药物的杀伤作用。使用VP联合ibrutinib或R788具有明显的协同作用。进一步探讨机制，我们发现干扰YAP可明显抑制G1期相关蛋白的表达，抑制BCR信号通路及PI3K-AKT信号通路的活化、促进细胞凋亡及DNA损伤相关信号通路分子的表达，从而通过对多条信号通路的调控达到抑制细胞增殖，促进细胞凋亡及增加药敏的作用。因此，本研究首次证实Hippo信号通路异常活化可能与B-NHL的发病及耐药相关，靶向Hippo信号通路关键分子YAP可能成为B-NHL尤其是复发难治B-NHL潜在治疗靶点。