中文摘要：

背景与目的：肿瘤的多药耐药（multidrug resistance，MDR）基因的表达是目前化疗失败的主要原因，磷脂酰肌醇-3-激酶（phosphoinositide 3-kinases，P13K）信号通路参与肿瘤多药耐药的发生，但P13K信号通路与多药耐药的机制尚不明确。本研究旨在探讨P13K／Akt信号通路及其下游靶点对ATP结合蛋白亚家族1抗体（ATP-bindingcassettesub-familyBmember1，ABCBI）基因编码的P-糖蛋白（p-glycoprotein，P-gp）介导的人结肠癌耐奥沙利铂细胞株HCT-116／L-0HP细胞多药耐药性的调控作用。方法：将PI3κ特异性抑制剂LY294002（20pmol／L）处理人结肠癌HCT-116／L-OHP细胞2h后，用细胞计数试剂盒-8（cellcountingkit-8，CCK一8）检测细胞对奥沙利铂的敏感性；蛋白质印迹法（Westernblot）检测相关耐药蛋白P-gp、肺耐药蛋白（1ungresistance-refatedprotein，LRP）、多药耐药相关蛋白-2（multidrugresistance-related-2，MRP-2）以及P13K／Akt信号通路下游蛋白Akt、p-Akt、IKB、p-IKB的表达变化；CHIP--PCR法检测核转录因子KB（NF—KB）对4BC8J基因启动子的影响。结果：阻断P13K／Akt信号通路激活后，奥沙利铂对HCT-116／L-0HP细胞的半数抑制浓度（Ic。。）由（157．48±16．73）pg／mL降至（53．68±3．18）9g／mL，逆转指数为2．93（P〈0．01）。HCT-116／L-OHP细胞的P-Akt、p-IKB和P-gp的表达水平明显下降（P〈O．01），Akt、IKB、LRP和MRP-2表达变化不明显。NF-KB能够与ABCBI基因启动子区域结合。结论：阻断P13K／AKT信号通路可增强人结肠癌HCT-116／L-OHP耐药细胞的药物敏感性，抑Slip-Akt和P-IKB的磷酸化表达水平，逆转P-gP介导的肠癌多药耐药。

英文摘要：

Background and purpose： Multidrug resistance （MDR） is the dominating obstacle to the chemotherapy. There is strong evidence that the phosphoinositide 3-kinases （PI3Ks） signaling pathway is involved in MDR phenotype, however, the mechanism of MDR occurrence is still unknown. This study tended to investigate the regulating effect of PI3K/Akt signaling pathway and its downstream target genes in P-glycoprotein （P-gp） （ABCB1 gene encoding）-mediated MDR in human colon carcinoma HCT-116/L-OHP cells. Methods： Pretreatment with PI3Kselective inhibitor LY294002 （20 μmaol/L） for 2 h, the sensitivity of L-OHP was evaluated by the CCK-8 （cell counting kit-8） assay in HCT-116/L-OHP cells, and the expressions of P-gp, LRP, MRP-2, Akt, p-Akt, IκB and p-InB were evaluated by Western blot. The activity of ABCB 1 promoter was evaluated by chromatin immunoprecipitation analysis （CHIP）. Results： After inhibiting the activity of PI3K/Akt signaling pathway, the IC50 value of L-OHP decreased from（157.48±16.73） μg/mL to （53.68±3.18） μg/mL in HCT- 116/L-OHP cells, and the reversal index was 2.93 （P〈0.01）. The expressions of P-gp, p-Akt and p-IvJ3 were down-regulation compared with the concrol group （P〈0.01）, but the expressions of LRP, MRP-2, Akt and IKB didn＇t change significantly. CHIP result has confirmed that NF-nB protein could bind to the region ofABCB 1 gene promoter in HCT 116/L-OHP cells. Conclusion： Blocking of PI3K/Akt/NF-kB signal pathway could increase the drug sensitivity to MDR cells, inhibit the phosphorylation of p-Akt and p-IκB, and reversing ABCB 1/P-glycoprotein-mediated multidrug resistance in colon carcinoma cells.