磷脂酰肌醇3激酶β(PI3Kβ)和PI3Kδ在KIT突变介导的细胞转化中起不同作用

PI3K isoforms PI3Kβ and PI3Kδ play different roles in KIT mutation-mediated cell transformation

目的探究磷脂酰肌醇3激酶(PI3K)的不同亚型在三型酪氨酸激酶受体KIT突变介导的信号传递及细胞增殖中的作用。方法在BaF3细胞中稳定表达野生型KIT及胃肠间质瘤中常见的KIT突变V560D、 W557K558del,分别用PI3Kα、 PI3Kβ、 PI3Kδ亚型特异性抑制剂或者广谱PI3K抑制剂处理细胞,免疫沉淀法和Western blot法检测KIT及其下游信号活化情况。胃肠间质瘤GIST-T1细胞采用相同药物及浓度处理,免疫共沉淀和Western blot法检测KIT及其下游信号的活化情况,噻唑蓝(MTT)法检测细胞增殖,流式细胞术检测细胞凋亡。结果与对照组相比,在表达野生型KIT及其突变体的BaF3细胞中, PI3Kδ亚型特异性抑制剂对KIT及其下游信号分子蛋白激酶B(AKT)和胞外信号调节激酶(ERK)活化的抑制作用最强,其次为PI3Kα和PI3Kβ亚型特异性抑制剂。在GIST-T1细胞中, PI3Kβ亚型特异性抑制剂对KIT及其下游信号活化的抑制作用最强,其次为PI3Kδ和PI3Kα亚型特异性抑制剂。结论在BaF3细胞中, PI3Kδ亚型在KIT活化及其下游信号传递中起主要作用,而在GIST-T1细胞中, PI3Kβ亚型在KIT活化及其下游信号传递中起主要作用,这些结果表明不同PI3K亚型在KIT突变介导的细胞转化中起不同作用,且在不同的细胞中其作用也有不同。

Objective To investigate the role of phosphatidylinositol 3-kinase(PI3K) isoforms in type Ⅲ receptor tyrosine kinase KIT mutation-mediated signaling and cell proliferation. Methods The wild-type KIT and the common KIT mutations V560D and W557K558del in gastrointestinal stromal tumors(GIST) were stably expressed in BaF3 cells. The cells were treated with PI3K isoforms PI3Kα, PI3Kβ and PI3Kδ specific inhibitors or pan PI3K inhibitor. The activation of KIT and its downstream signals was detected by immunoprecipitation and Western blot analysis. GIST-T1 cells were treated with the same drug, and the activation of KIT and its downstream signals was also detected by immunoprecipitation and Western blot analysis, and cell proliferation and apoptosis were detected by MTT assay and flow cytometry, respectively. Results Compared with the controls, in BaF3 cells expressing wild-type KIT and its mutants, the activation of KIT and its downstream signaling molecules AKT and ERK was inhibited the most by PI3Kδ specific inhibitor, followed by the specific inhibitors of PI3Kα and PI3Kβ subtype. In GIST-T1 cells, the activation of KIT and its downstream signals was inhibited the most by PI3Kβ specific inhibitor, followed by PI3Kδ and PI3Kα specific inhibitors. Conclusion In BaF3 cells, PI3Kδ subtype plays a major role in KIT activation and its downstream signal transduction, while in GIST-T1 cells, PI3Kβ subtype plays a major role in KIT activation and its downstream signal transduction. These results indicate that PI3K isoforms play different roles in KIT mutation-mediated cell transformation depending on the host cells.