MORN3通过调控细胞自噬影响肿瘤细胞耐受顺铂治疗的机制研究

Autophagy helped cancer cells to resist outside pressure and lethal effect of chemotherapeutic drugs, but the molecular mechanism of how autophagy regulated tumor cells’ resistance to chemotherapeutic drug is not very clear. The MORN3 protein has been found expressed in mouse testis tissue with unknown function. Our recent study showed that MORN3 was expressed highly in some colorectal cancer and held obvious colocalization with LC3 inside cells. Moreover, MORN3 significantly enhanced autophagy level in tumor cells and inhibited the tumor-killing effect of cisplatin. However, the concrete mechanism of how MORN3 tuned autophagy and tumor cell’s resistance to chemotherapy medicine remains undiscovered. This project intends to explore molecular mechanism about how MORN3 participated in regulating autophagy process in cancer and tumor cell’s resistance to chemotherapy, to identify the key proteins interacted with MORN3 and their interaction sites, to intervene MORN3’s expression and expound its influence on tumor cells’ chemotherapy sensitivity and to evaluate the value of MORN3 quantity as a molecular marker of patients’ prognosis as well as to provide the theory basis for finding new targets of tumor’s resistance to cisplatin.

细胞自噬会帮助癌细胞抵抗外界压力和化疗药物的杀伤作用，但其调控的具体分子机制未明。MORN3是一种功能未知的蛋白，主要表达在睾丸组织中。我们近期发现MORN3在部分大肠癌中高表达，与LC3蛋白在细胞内共定位。并且，MORN3促进肿瘤细胞发生自噬并抑制顺铂对肿瘤细胞的杀伤作用。然而，MORN3调控肿瘤细胞自噬与耐药的具体机制并不清楚。本项目拟结合体内外实验和临床队列研究，探索MORN3参与调控癌细胞自噬过程和化疗耐受的分子机制，识别MORN3的关键相互作用蛋白与位点，干预MORN3的表达并阐明其对肿瘤细胞化疗敏感性的影响，分析肿瘤标本中MORN3的表达量作为患者预后的标志物的价值，为发现顺铂耐药的新的靶点提供理论依据。

针对程序性细胞死亡配体1（PD-L1）以及程序性死亡受体1（PD-1）的免疫检查点的阻断治疗促进了T细胞对肿瘤细胞的免疫监测，并给癌症患者带来了较好的临床治疗效果。PD-L1抗体可以通过封闭肿瘤细胞表面的PD-L1蛋白，从而阻止PD-L1介导的肿瘤细胞免疫逃逸。但是，细胞内贮存的PD-L1会不断地补充并且重新分布到细胞膜上，从而降低PD-L1抗体的治疗效果。所以靶向肿瘤细胞整体的PD-L1，包括细胞膜上的和细胞内贮存的PD-L1显得尤为重要。通过检测PD-L1棕榈酰化水平和位点，发现PD-L1的胞内区段的272位的半胱氨酸会发生棕榈酰化修饰，这种脂质修饰会通过抑制PD-L1单泛素化来稳定PD-L1，从而阻断其通过多囊体-溶酶体降解途径。通过对棕榈酸酰基转移酶家族的筛选，鉴定出DHHC3是PD-L1棕榈酰化所需要的特异的酰基转移酶。通过2-溴棕榈酸（2-BP）或者沉默DHHC3抑制PD-L1棕榈酰化，可分别在体外和小鼠体内激活抗肿瘤免疫。通过分析并验证PD-L1蛋白中发生棕榈酰化修饰的序列，设计了一种竞争性抑制PD-L1棕榈酰化的多肽，它可以降低肿瘤细胞中PD-L1的表达，增强T细胞的抗肿瘤效应。这些发现为解决PD-L1介导的肿瘤免疫逃逸提供了新的策略和方法。