重组人生长激素减少人结肠癌细胞株放疗诱导的细胞凋亡

Recombinant human growth hormone reduces the radiotherapy induced apoptosis on colorectal cancer cells

目的:探讨重组人生长激素(rhGH)对结肠直肠癌细胞株放疗敏感性的影响,并研究其与细胞凋亡的关系。方法:应用流式细胞术及免疫荧光法检测9个人结肠直肠癌细胞株表面生长激素受体(GHR)的表达水平;应用克隆形成实验检测结肠直肠癌细胞经照射后的增殖能力,从而评估其放疗敏感性;应用流式细胞术(Annexin V-FITC染色)检测放疗诱导的细胞凋亡;应用Western blot方法检测rhGH干预后Akt磷酸化水平的变化。结果:从9个细胞株中选择HCT-8为GHR阳性表达细胞,LoVo细胞为阴性表达对照。rhGH显著提高了GHR阳性表达的HCT-8细胞经放疗后的克隆形成率[在高剂量8Gy照射下尤为明显,(52.1±2.9)%比(21.0±2.7)%,P<0.001],同时减少了细胞凋亡(P<0.05);而对GHR阴性表达的LoVo细胞作用不明显(P>0.05)。rhGH能诱导HCT-8细胞Akt快速磷酸化,呈PI-3K依赖(P<0.001)。结论:rhGH使GHR阳性表达的结肠直肠癌细胞对放疗有抵抗作用,这种作用可能与其减少细胞凋亡有关。

Objective To test the effect of recombinant human growth hormone （rhGH） on the radiotherapy sensitivity of colorectal cancer cell line, and to explore its relationship with apoptosis. Methods Flow cytometry and immunofluorescence were used to detect growth hormone receptor（GHR） expression on 9 human colorectal cancer cell lines. The colony forming assay was performed to measure the post-radiotherapy colorectal cancer cell proliferation as an indicator of radiotherapy sensitivity. Flow cytometry （Annexin V-FITC staining） was used to detect the radiotherapy induced apoptosis; Western blot was performed to detect the phosphorylated Akt level within the same cell lines. Results HCT-8 GHR positive expression cell and LoVo GHR negative expression cells were selected for further studies. The colony formation rate was significantly enhanced in HCT-8 cells pre-incubated with rhGH as compared to the radiotherapy group cells and in a dose dependent manner（0-100 mg/L）; under high doses （8 Gy）, this effect was more dramatic （52.1±2.9 vs 21.0±2.7, P〈0.001）.rhGH pre-incubation also reduced radiotherapy induced HCT-8 cell apoptosis （P〈0.05）. When GHR was blocked with neutralizing antibodies, this protective effect was eliminated. By contrast, rhGH pre-incubation did not change the colony formation rate in GHR negative expression LoVo cells. GH rapidly induced Akt phosphorylation in HCT-8 cells by GH/GHR signaling, and this effect was blocked by PI-3 kinase inhibitor. Conclusions The protective effect of GH on colorectal cancer cells may occur after radiotherapy exposured by GHR, which is related to the reduction of apotosis.