重组人生长激素对人结肠癌细胞株放疗诱导所致DNA损伤修复的研究

目的探讨重组人生长激素（recombinanthumangrowthhormone，rhGH）对结直肠癌细胞株放疗敏感性的影响，并研究其与DNA损伤修复的关系。方法应用流式细胞术，检测人结直肠癌细胞株表面GHR表达水平；应用克隆形成实验，检测结直肠癌细胞经照射后增殖能力并评估放疗敏感性；应用彗星电泳法，检测放疗诱导的细胞DNA损伤：应用westernblot方法，检测DNA损伤修复基因GADIM5、APEN表达水平。结果从9株细胞株中选择GHR表达水平最高（58．23％）的HCT-8细胞为实验细胞，LOVO细胞（0．2％）为阴性对照。rhGH显著提高了GHR（＋）HCT-8细胞放疗后的克隆形成率（P〈0．001），并且这种作用呈剂量依赖（P=0．762）；而对GHR（-）的lovo细胞作用不明显（P〉0．05）。rhGH干预使HCT-8细胞DNA初始受损程度显著下降（P=0．003），并且在到达平台期后其水平与单纯放疗相比也明显下降（P=0．012）。rhGH显著上调了HCT-8细胞DNA损伤修复基因GADD45、APEN蛋白表达水平（P〈0．001．P=0．007）。结论rhGH对GHR（＋）的结直肠癌细胞具有放疗保护作用，这可能与其激活细胞内DNA损伤修复基因，从而增强了DNA损伤修复能力有关。

Recombinant Human Growth Hormone Reduces the Radiotherapy Induced DNA Damage on GHR(+)Colorectal Cancer Cells

Objective To test the effect of recombinant human growth hormone （ rhGtt ） on colorectal cancer cell line radiotherapy sensitivity, and explore its relationship with DNA damage and repair. Methods The flow cytometry was performed to detect GHR expression on 9 human eolorectal cancer cell lines;The colony forming assay was performed to measure the post-radiotherapy colorectal cancer cell proliferation as an indicator of radiotherapy sensitivity. The comet assay was performed to detect the radiotherapy induced DNA damage;The western blot was performed to detect GADD5 and APEN expression within the same cell lines as described previously. Results HCT-8 GHR （ ＋ ） cell and LOVO GHR （ - ） cell are selected for further study. The colony formation rate is significantly enhanced in HCT-8 cells pre-incubated with rhGH compared to the radiotherapy group cells and with a dose dependent mamler （ 0 - 100 mg/l, P = 0. 762 ）, Under high doses （ 8 Gy ） this effect is more dramatic （ P 〈 0. 001 ）. When GHR is blocked with neutralizing antibodies, this protective effect is eliminated. By contrast, rhGH pre-incubation does not change the colony formation rate in GHR（ - ） LOVO cells, rhGH intervention reduces the early HCT-8 cell DNA damage （ P = 0. 003） Moreover,r-hGH intervention reduces DNA damage even after platform phase compared to radiotherapy alone. （ P = 0.012）. This effect is eliminated by GHRA pre-treatment, rhGH up-regulates GADD45 and APEN expression which are closely related to cellular stress response and DNA damage-repair （ P = 0. 007 ）. Conclusion Our results demonstrate the protective effect of GH on eoloreetal cancer cells ＇after radial exposure by GHR, which is related to the promotion of DNA damage rapair aetivity.