法尼酯X受体的类泛素化修饰对胆囊癌细胞化疗敏感性的影响及其机制研究

Gallbladder cancer (GBC) cells, in which reactive oxygen species (ROS) level is lower, is not sensitive to chemotherapy. Apoptosis plays a leading role in chemotherpy. Our previous finding first showed that increasing ROS could enhance chemosensitivity of GBC cells, but the mechanism is still not well known. As a nuclear receptor for bile acids, farnesoid X receptor (FXR) plays an important role in development of bile duct tumors, but its effect on drug resistance has not yet been reported. Our preliminary experiment showed that increasing ROS could induce FXR de-sumoylation, then activate FXR. Moreover, activating FXR could enhance chemosensitivity of GBC cells, which might attribute to downregulation of STAT3/5 mediated expression of anti-apoptotic protein induced by upregulation of small heterodimer partner (SHP). So via the cell, animal and clinical experiments, we will for the first time reveal that through upregulating SHP expression, activation of FXR induced by FXR de-sumoylation may downregulate STAT3/5 mediated expression of anti-apoptotic protein, which may enhance chemosensitivity, and further prove that FXR de-sumoylation is the reason why increasing ROS level may enhance chemosensitivity in GBC. The study will focus on mechanisms of sumoylation regulating transcriptional activity of FXR and influence of ROS on FXR sumoylation. In conclusion, our study will clarify mechanisms of drug resistance and certify the feasibility of ROS generator used to enhance therapeutic effect in GBC.

胆囊癌细胞活性氧（ROS）水平较低，对化疗不敏感。细胞凋亡是肿瘤化疗杀伤的主要途径。我们的前期研究首次发现升高ROS能提高胆囊癌细胞的化疗敏感性，但机制未阐明。法尼酯X受体（FXR）是胆汁酸核受体，与胆道肿瘤发生有关，但与化疗耐药的关系无人研究。我们的预实验首次发现升高ROS能降低FXR的类泛素化修饰，提高FXR的转录活性；激活FXR能提高胆囊癌细胞的化疗敏感性，机制可能与小异二聚体（SHP）表达升高导致炎症因子STAT3/5对抗凋亡蛋白的转录降低有关。因此我们将从细胞、动物、临床标本三个层面首次阐述：ROS↑→FXR的类泛素化修饰↓→FXR的转录活性↑→SHP表达↑→STAT3/5活性↓→抗凋亡蛋白表达↓→胆囊癌细胞化疗敏感性↑。重点阐述类泛素化修饰对FXR转录活性的调控及ROS对FXR的类泛素化修饰的调控。这有助于胆囊癌耐药机制的阐明，为活性氧生成剂提高胆囊癌疗效提供理论依据。

胆道恶性肿瘤主要包括胆囊癌和胆管癌，耐化疗是影响胆道恶性肿瘤疗效的主要原因之一，因此我们要寻找有效的化疗药物。该研究首次发现法尼酯X受体（FXR）激动剂GW4064和鹅脱氧胆酸（CDCA） 活化FXR能够明显增强常用化疗药物顺铂（CDDP）对胆道恶性肿瘤细胞的杀伤作用，并且该效应主要通过凋亡途径实现，其机制为：活化FXR能够刺激小异二聚体伴侣（SHP）的表达，从而协同CDDP抑制STAT3的磷酸化，下调抗凋亡蛋白Bcl-xL的表达，逆转胆道恶性肿瘤细胞对CDDP的耐药。并且，通过裸鼠移植瘤模型在体内也证实了上述观点。该研究为解决胆道恶性肿瘤耐药提供了新思路，为FXR激动剂将来应用于胆道恶性肿瘤的临床治疗提供了实验依据，具有一定的转化医学意义。