抑癌因子Sufu在颗粒性神经元前体细胞恶性转化的作用机制研究

Hedgehog (Hh) is a major developmental morphogen that regulates pattern formation and cell fate in vertebrates. Hh signal is essential for proliferation of granular neuron precursor cells (GNPCs) in external granule layer of cerebellum. Aberrant activation of the Hh pathway, which induces uncontrolled proliferation of GNPCs, causes medulloblastoma. Recent clinical trial data indicates that Hh signaling blockade is an effective anti-cancer therapy. Smo, a membrane receptor of Hh signaling, is the only target of antineoplastic drug of Hh-relative cancer. However, Smo antagonists in trials can lose their efficacy due to the presence of drug-resistance mutations in tumors, making the development of additional drug targets in other parts of the Hh pathway an urgent need. Sufu is a key downstream inhibitory regulator that binds and controls Gli transcription factors of the Hh pathway. Our group has been working on the function and regulatory mechanisms of Sufu in Hh pathway for nearly 10 years. In this proposed research, we plan to determine a new regulatory target in Shh signaling, and to provide a novel drug-target for Shh-dependent anti-cancer therapy. We propose 1) to elucidate the role and mechanism of Sufu and its potential interacting proteins in Hh-related tumorigenesis; 2) to demonstrate the function and mechanism of Sufu in malignant transformation of GNPCs; and 3) to explore biological significance of Sufu and its its potential interacting proteins in Smo antagonists-resistant medulloblastoma.

Hedgehog（Hh）是调控组织形态发生和细胞定向分化的主要形态发生因子。Hh信号为促小脑外颗粒层颗粒性神经元前体细胞（GNPCs）增殖所必需，但Hh通路异常活化导致GNPC细胞癌变和髓母细胞癌（MB）的发生。目前针对Hh信号的抗肿瘤治疗仅针对Smo单一靶点,临床会因Smo基因突变而耐药。因此,寻找通路中新的治疗靶点迫在眉睫。Sufu是Smo下游重要的负向调控因子, 与肿瘤发生关系密切。本课题组长期致力于Sufu蛋白自身调控机制的研究。本研究旨在确立以Sufu为核心的新的Hh信号转导调控靶点,为寻找治疗髓母细胞癌的小分子化合物提供崭新的思路与可能的新靶点。为此我们将1）阐明Sufu及其潜在的结合蛋白在Hh信号依赖的肿瘤发生中的作用，及其自身活性的调控机制；2）揭示Sufu在颗粒性神经元前体细胞恶变进程的生理作用和机制；和3）探索Sufu及其结合蛋白对Smo抑制剂耐药MB发生的调控意义。

Sonic Hedgehog（Shh）是调控组织形态发生的主要形态发生因子，Shh通路异常活化导致髓母细胞癌（MB）的发生。目前，针对Shh信号的小分子靶向治疗仅针对Smo单一靶点，临床会因Smo基因突变而耐药，寻找通路中新的治疗靶点迫在眉睫。Sufu是Smo下游重要的负向调控因子，与肿瘤发生关系密切。本研究旨在确立以Sufu为核心的新的Hh信号转导调控靶点,为寻找治疗髓母细胞癌的小分子化合物提供崭新的思路与可能的新靶点。我们研究发现：1）Sufu蛋白与Hh通路下游转录因子Gli蛋白偶联，在细胞内协同转运，调控Hh信号转录应答的新分子机制。2）磷酸化修饰促进Sufu对髓母细胞癌的抑制作用增强，其机制可能与抑制Hh信号下游的Gli转导活性和细胞的多胺代谢有关。3）利用蛋白质组学方法，确定与Sufu相互作用的蛋白磷酸酶4调节亚基2（Ppp4r2）。蛋白磷酸酶4（Ppp4）使Sufu去磷酸化，从而促进其降解和下游Gli1转录活性。Ppp4介导的Sufu的去磷酸化促进了髓母细胞癌细胞的细胞增殖。