UGT1促进P-gp糖基化参与调节胃癌多药耐药

Gastric cancer is the second leading cause of cancer mortality worldwide. The major cause of treatment failure for gastric cancer is the development of multidrug resistance (MDR) to chemotherapy, which is one of the primary treatment options.But the underlying mechanisms of MDR are still not clear. Glycosylation is considered as one of the most important and common protein post-translational modifications and is associated with drug resistance in many tumors. But currently, there is no report about the relation between glycosylation and MDR in gastric cancer. Previously we performed MDR related glycoproteomics research in gastric cancer and found that the total glycosylation level in MDR cell lines are increased compared with that in parental gastric cancer cell. Then we examined several common glycosylases and found UDP-glucose:glycoprotein glucosyltransferase 1 (UGT1), which could promote glycosylation, was dramatically increased in gastric cancer MDR cells. Subsequently, we found that the glycosylation level of P-glycoprotein was significantly higher in UGT1 up-regulated cells than that in control cells. Therefore, it suggested that UGT1 may promote the development of MDR in gastric cancer by up-regulating glycosylation on P-gp protein.In this subject, firstly we are planning to investigate the role of UGT1 in MDR of gastric cancer. Then the mechanisms by which glycosylated P-gp would mediate the promotional effect of UGT1 on MDR in gastric cancer. Finally, the clinical value of UGT1, total P-gp and glycoaylated P-gp in gastric cancer will be determined. This work would be not only helpful to clarify the function of UGT1 in MDR of gastric cancer, but also be helpful to better understand the significance of glycosylation in cancers and the developent of MDR in gastric cancer, and valuable for prevention and turnover of MDR in gastric cancer.

多药耐药是导致胃癌化疗失败，患者死亡的重要因素，其机制尚未完全阐明。糖基化是最重要的蛋白翻译后修饰之一，与多种肿瘤的耐药表型密切相关，但目前尚无与胃癌多药耐药的研究。本项目前期研究发现胃癌多药耐药细胞中蛋白总体糖基化水平升高，而能够促进糖基化的糖基转移酶UGT1在耐药细胞中表达明显升高，且高表达UGT1的细胞中P-gp糖基化水平明显升高，提示UGT1可能通过促进P-gp的糖基化，参与调节胃癌的耐药表型。本项目拟在前期基础上，进一步研究UGT1对胃癌细胞耐药性的影响；通过各种体内、外实验探讨UGT1通过上调P-gp糖基化，促进胃癌耐药的机制；最后通过胃癌组织标本明确UGT1、总P-gp及糖基化P-gp的临床意义。本项目将有助于深入诠释UGT1参与调节肿瘤多药耐药的分子机理，明确蛋白糖基化在胃癌多药耐药过程中的作用，并最终对于阐明胃癌多药耐药的产生机制具有重要指导意义。

蛋白糖基化在肿瘤多药耐药中发挥着重要作用。前期我们发现胃癌多药耐药细胞中蛋白总体糖基化水平升高，而能够促进糖基化的糖基转移酶UGT1在耐药细胞中表达明显升高，且高表达UGT1的细胞中P-gp糖基化水平明显升高，提示UGT1可能通过促进P-gp的糖基化，参与调节胃癌的耐药表型。本课题中，我们深入研究了UGT1在胃癌细胞多药耐药过程中的作用及相关作用机制，发现：1.在胃癌耐药细胞SGC7901/ADR和SGC7901/VCR中，UGT1的表达明显高于对照胃癌亲本细胞SGC7901，而经化疗药物诱导后，胃癌亲本细胞SGC7901中UGT1的表达明显上调；2.UGT1通过增加化疗药物外排、抑制化疗药物引起的凋亡等途径，最终使SGC7901细胞的耐药性增加；3.在SGC7901细胞中转染P-gp正义表达载体仅能增加非糖基化P-gp蛋白水平，而转染UGT1后则同时可增加糖基化与非糖基化2种形式的P-pg表达水平，说明UGT1可上调P-gp的糖基化水平；4. 用衣霉素处理胃癌细胞，抑制蛋白糖基化修饰后，糖基化形式的P-gp蛋白水平明显降低，细胞的药物泵出能力明显减弱，最终导致耐药性的产生；5.耐药细胞中降低UGT1表达可明显恢复细胞对化疗药物的敏感性，这一过程可通过上调糖基化形式P-gp蛋白水平来逆转，说明UGT1调节胃癌细胞的耐药性主要是通过糖基化形式的P-gp蛋白实现的。上述研究成果有助于深入诠释UGT1参与调节肿瘤多药耐药的分子机理，明确蛋白糖基化在胃癌多药耐药过程中的作用，最终对于阐明胃癌多药耐药的产生机制具有重要指导意义。

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