含CYP2E1基因的重组腺病毒载体转染人骨髓间充质干细胞联合达卡巴嗪的抗肿瘤效应

目的 构建含人细胞色素P-450 CYP2E1(CYP2E1)基因的缺陷型重组腺病毒载体,检测其协同化疗药物的抗肿瘤效应,为基因介导酶前药治疗提供新的思路.方法 克隆人肝CYP2E1全长cDNA,制备高滴度的重组腺病毒颗粒(1.2×1012 pfu/ml).分离、培养、传代纯化及鉴定人骨髓间充质干细胞(BMSC).用Transwell小室检测BMSC向肿瘤细胞的趋化迁移.将重组腺病毒分别转染BMSC和人黑色素瘤细胞A375细胞.荧光显微镜和RT-PCR、Western印迹法分别检测转基因细胞中外源增强绿色荧光蛋白(EGFP)、CYP2E1的表达.倒置显微镜、四甲基偶氮唑盐(MTT)和膜联蛋白V-异硫氰酸荧光素(Annexin V-FITC)和碘化丙啶(PI)双染色法检测CYP2E1协同酶前药达卡巴嗪(DTIC)的抗肿瘤效应(实验分A375-CYP2E1组、BMSC-CYP2E1组和BMSC-CYP2E1+A375组,并以各自空载体组作为对照;细胞接种后分别加入不同浓度DTIC).结果 成功构建重组腺病毒载体pAd5CMV-NpA-CYP2E1和pAd5CMV-NpA-EGFP.成功分离BMSC,并证明BMSC可通过聚碳酸酯膜分别向下室内的K562和A375细胞迁移.荧光显微镜检测到转基因靶细胞EGFP表达,RT-PCR和Western印迹法均检测到目的基因在转基因细胞中高表达.倒置显微镜下见加入DTIC后BMSCCYP2E1+A375组的死亡细胞明显多于对照组.MTT法示DTIC呈浓度依赖性抑制转CYP2E1基因的细胞生长,其中BMSC-CYP2E1+A375组药物半数抑制量(IC50)值为(0.17±0.13)mmol/L,其对照组为(0.65±0.20)mmol/L,二者差异有统计学意义(P＜0.01),可选0.05 mmol/L DTIC浓度作人BMSC的相对安全浓度.Annexin V/PI法示0.05 mmol/L DTIC处理细胞48 h后BMSC-CYP2E1+A375组细胞凋亡率明显高于其对照组(26.8±2.0比8.7±1.3,P＜0.01).结论 BMSC体外具有向肿瘤细胞趋化迁移的特性.重组腺病毒载体介导的CYP2E1转染BMSC具有协同化疗前药的抗肿瘤效应.

Construction of CYP2E1 recombinant adenovirus vector and its anti-tumor effects

Objective To construct the human cytochrome P-450 CYP2E1 (CYP2E1) recombinant adenovirus vector and detect its anti-tumor effects in combination with chemotherapeutic drugs so as to provide rationales for gene directed enzyme prodrug therapy ( GDEPT) . Methods CYP2E1 cDNA was cloned from human liver and a recombinant adenovirus vector constructed at a titer of 1 x 1012 pfμ/ml. Human bone marrow-derived mesenchymal stem cells ( BMSCs) were separated, cultured, purified and detected. The tropism of BMSCs for cancer cells was detected by Transwell technique. These recombinant vectors were transferred into BMSCs and A375 cells and the expressions of EGFP and CYP2E1 detected by fluorescence microscope, RT-PCR and Western blot respectively. Inverted microscope, MTT and Annexin V-FTTC/PI were employed to detect the anti-tumor effect of CYP2E1 recombinant adenovirus vectors in combination with chemotherapeutic prodrug dacarbazine ( DTIC) . Results The recombinant adenovirus vectors pAd5CMV-NpA-CYP2El and pAd5CMV-NpA-EGFP were constructed successfully. BMSCs were successfully separated and they could migrate in vitro through a polycarbonate filter toward K562 and A375 cells in the lower chamber. Fluorescence microscope was used to detect the expression of EGFP while both RT-PCR and Western blot revealed a high expression of CYP2E1 in gene-transfected group cells. The dead cell counts of co-culture group of gene-transfected BMSCs and wild type A375 cells were significantly higher than those of the control under inverted microscope. The results of MTT showed that the growth inhibition of gene-transfected group cells was increased with DTIC concentration in a concentration dependent manner. IC50 of group BMSCs-CYP2El + A375 was (0. 17 ±0. 13) mmol/L, and that of the control group was ( 0. 65 ± 0. 20) mmol/L ( P < 0. 01). The DTIC concentration at which BMSCs were relatively safe might be selected at 0.05 mmol/L. Annexin V-FITC/PI confirmed that the apoptosis rate of BMSCs-CYP2E1 + A375 group was significantly higher than that of the control group after a 48-hour treatment of 0. 05 mmol/L DTIC (26. 8 ±2. 0 vs 8. 7 ± 1. 3, P < 0. 01). Conclusion With an in vitro tropism for cancer cells, BMSCs transferred with CYP2E1 recombinant adenovirus vectors have anti-tumor effects probably synergistically with chemotherapeutic drugs.