Song Shuzheng, Pei Guoqing, Du Yaqiong, Wu Jugang, Ni Xiaochun, Wang Shoulian, Jiang Bojian, Luo Meng, Yu Jiwei
Department of General Surgery, Shanghai Ninth People's Hospital, School of Medicine, Shanghai Jiao Tong UniversityShanghai 201999, China.
Am J Transl Res. 2018 Jan 15;10(1):304-314. eCollection 2018.
Chemoresistance in gastric cancer is the leading cause of tumor recurrence and poses a substantial therapeutic challenge. The stem cell biomarker CD133 has been implicated in drug resistance of tumor-initiating cells in a number of cancers including gastric cancer. Therefore, we investigated the molecular mechanism of CD133-associated multidrug resistance in gastric cancer cells. Using CD133 overexpressing and knockdown gastric cancer cell lines, we demonstrated that loss of CD133 significantly increased the growth inhibition of chemotherapeutic agents; whereas, overexpression significantly reduced growth inhibition. Furthermore, CD133 knockdown significantly reduced the enzymatic activity of phosphatidylinositol-3 kinase (PI3K) and the expression of P-glycoprotein (P-gp), B-cell lymphoma 2 (BCL2), and phosphorylated-protein kinase B (p-AKT), but elevated the expression of BCL2 associated X (BAX). Conversely, overexpression of CD133 significantly increased PI3K enzymatic activity, expression of P-gp, BCL2, and p-AKT, and decreased BAX expression. The PI3K/AKT inhibitor LY294002 mirrored the effects of loss of CD133; whereas, the PI3K/AKT activator epidermal growth factor reproduced the effects of CD133 overexpression. To identify the interaction between CD133 and PI3K, we used site-directed mutagenesis to mutate individual tyrosine residues of CD133. We found that binding between CD133 and p85, the regulatory subunit of PI3K, was significantly reduced when tyrosine 852 was mutated. In summary, we have demonstrated that CD133 activates the PI3K/AKT signal transduction pathway through direct interaction with PI3K-p85, resulting in multidrug resistance of gastric cancer cells. These results suggest that the interaction between CD133 and PI3K-p85 may offer a novel therapeutic target in multidrug resistant gastric cancer.
胃癌中的化学抗性是肿瘤复发的主要原因，并构成了重大的治疗挑战。干细胞生物标志物CD133已被证明与包括胃癌在内的多种癌症中的肿瘤起始细胞的耐药性有关。因此，我们研究了胃癌细胞中CD133相关多药耐药的分子机制。使用过表达和敲低CD133的胃癌细胞系，我们证明CD133的缺失显著增加了化疗药物的生长抑制作用；而过度表达则显著降低了生长抑制作用。此外，CD133敲低显著降低了磷脂酰肌醇-3激酶（PI3K）的酶活性以及P-糖蛋白（P-gp）、B细胞淋巴瘤2（BCL2）和磷酸化蛋白激酶B（p-AKT）的表达，但增加了BCL2相关X蛋白（BAX）的表达。相反，CD133的过度表达显著增加了PI3K酶活性、P-gp、BCL2和p-AKT的表达，并降低了BAX表达。PI3K/AKT抑制剂LY294002反映了CD133缺失的影响；而PI3K/AKT激活剂表皮生长因子再现了CD133过度表达的影响。为了确定CD133与PI3K之间的相互作用，我们使用定点诱变对CD133的单个酪氨酸残基进行突变。我们发现，当酪氨酸852发生突变时，CD133与PI3K的调节亚基p85之间的结合显著减少。总之，我们证明了CD133通过与PI3K-p85直接相互作用激活PI3K/AKT信号转导通路，导致胃癌细胞的多药耐药。这些结果表明，CD133与PI3K-p85之间的相互作用可能为多药耐药胃癌提供一个新的治疗靶点。
