增殖抑制基因抑制乳腺癌细胞生长和侵袭及其相关机制研究

Over expression of hyperplasia suppressor gene inhibits the malignant phenotype of breast cancer cell

目的研究增殖抑制基因（HSG）对乳腺癌MDA-MB-231细胞（简称231细胞）生物学行为的影响并对其作用机制进行探讨。方法构建HSG全长真核表达载体，通过脂质体瞬时转染法使其在231细胞中高表达，通过MTT比色实验检查肿瘤细胞的体外增殖能力、Matrigel穿膜实验检测肿瘤细胞体外侵袭能力和应用流式细胞术检测肿瘤细胞的细胞周期及凋亡情况；并应用GsT—pulldown法检测HSG高表达对乳腺癌细胞Ras蛋白活性的影响。结果将构建好的重组人HSG真核表达质粒pcDNA3-MYC-HSG转染至231细胞中，MTT比色实验结果显示HSG的过表达可以抑制肿瘤细胞的增殖；Matrigel侵袭实验显示转染HSG的肿瘤细胞的穿膜细胞数（HSG／231组，78．5个±5．8个）与转染空载体组（vector／231组，131．1个±14．5个）相比明显减少。流式细胞分析结果显示转染HSG／231组细胞出现了G0／G1期阻滞（56．3％±2．3％），且凋亡细胞的百分比与对照组（vector／231组为50．4％±1．9％）相比有所增加。Ras蛋白活性检测发现转染HSG／231组的乳腺癌细胞Ras蛋白活性明显下降。结论HSG表达上调可抑制高侵袭性231细胞的体外增殖和侵袭能力，使其出现G0／G1期细胞周期阻滞，并可促进细胞凋亡。HSG对乳腺癌细胞的抑制作用可能与其抑制细胞Ras活性有关。

Objective To investigate the effect of over expression of human hyperplasia suppressor gene （HSG） on proliferation, invasion, apoptosis and cell cycle of human breast cancer cells and to determine the relationship between HSG and Ras-dependent signaling pathway. Methods Full length HSG coding sequences were cloned into plasmid pcDNA3. 0. The recombinant plasmids were transfected into MDA-MB-231, a highly malignant breast cancer cell line. Vacant pcDNA3.0 was used as the control. MTT, Matrigel transwell assay and flow cytometric analysis were used to test for proliferation, invasion, cell cycle distribution and apoptosis of tumor cells after transient transfection of HSG. GST-pulldown and Western blotting assays were performed to investigate the activity of Ras protein. Results HSG transfection inhibited proliferation of MDA-MB-231 cells, and significantly decreased the number of invading cells in Matrigel transwell assay compared with the vector/231 group （78. 5 ±5.8 vs. 131.1 ± 14. 5 ）cells. FACS analyses demonstrated that compared with the vector/231 group, up-regulation of HSG promoted breast cancer cell apoptosis [ （35.8±4. 8 ） % vs. （ 25.6 ±3. 5% ）] and induced G0/G1 phase arrest [ （56. 3 ±2. 3 ） % vs. （50. 4 ±1.9% ） ] after transfection for 18 hours. Furthermore, GST-pulldown assay showed that overexpression of HSG remarkably decreased the activity of Ras （about 65% lower than control）. Conclusions HSG exibits multiple anticaneer functions in breast cancer cells including inhibition of proliferation and in vitro invasion, G0/G1 arrest and promotion of apoptosis. Besides, inhibition of Ras-dependent signaling pathway may be involved in these processes.