乏氧照射双敏感启动子HRE.CArG调控HSVtk基因对肺癌细胞的杀伤效应

Hypoxia/radiation dual-sensitive promoters enhance the toxicity of HSVtk-mediated gene-directed enzyme prodrug therapy in Lung Cancer Cells

目的观察乏氧照射后HRE.CArG融合性启动子诱导增强的绿色荧光蛋白(EGFP)在SPCA1和A549肺癌细胞株中的表达变化及乏氧照射诱导下该启动子驱动自杀基因HSVtk对肺癌细胞的杀伤作用。方法用聚乙烯亚胺转染法转染SPCA1和A549细胞,乏氧照射后24 h测EGFP表达强度;乏氧照射后24 h加入GCV,48 h后用MTT法测定细胞存活率。结果乏氧照射后转染pDNA.HRE.CArG.EGFP质粒的SPCA1和A549细胞EGFP表达强度分别是对照组的(3.37±0.23)倍和(3.10±0.28)倍(P<0.01);转染pDNA.HRE.CArG.HSVtk质粒的SPCA1和A549细胞存活率较对照组分别降低(63.23±2.31)%和(76.58±2.19)%(P<0.01)。结论质粒载体中包含的HRE.CArG元件对乏氧照射敏感,乏氧照射后通过诱导下游的HSVtk基因大量表达,使转染细胞对GCV的敏感性增高,而大大增加对SPCA1和A549细胞的杀伤效应。

Objective To observe the expression of the enhanced green fluorescent protein （EGFP） induced by chimeric hypoxia/radiation responsive elements （HRE. CArG） in existence of hypoxia and radiation in SKA1 and A549 lung cancer cells; to examine the toxicity of such promoters responsive to hypoxia and radiation to control the expression of HSVtk - mediated gene - directed enzyme predrug therapy （GDEPT） to kill lung cancer cells.Methods Transient transfectants with the EGFP- constructs were obtained by exposing the SKA1 and A549 cells to complexes of DNA, polyethylenimine （PEI） for efficient transfection. The cells were exposed to hypoxia and radiation 24 h after transfection. Relative EGFP fluorescence was measured by flow cytometery; HSVtk - constructs were transfected into the hypoxic and irradiated SKA1 and A549 cells,then the cells were exposed to media containing ganciclovir （GCV） for 24 h.Two days later,the cell growth rate was detected by MTT assay. Results The EGFP expression was increased in the transfected cells with plasmids of pDNA. HRE. CArG. EGFP. Compared with the corresponding aerobic/sham - irradiated sample transfected with the same plasmid, survival of SKA1 and A549 cells transiently transfected with the pDNA. HRE. CArG. HSVtk plasmid in hypoxia and radiation and GCV exposure group reduced （63.23 ± 2.31 ）% and （76.58± 2.19）%（ P 〈0.01） ,respectively. Conclusions The promoters we constructed respond to hypoxia and radiation.The addition of GCV to hypoxia and irradiation significantly reduces plasmid - transfected cells＇ survival.