5HRE和CEAp联合调控的TSST-1激活淋巴细胞特异杀伤CEA阳性肿瘤细胞

TSST-1 regulated synergistically by 5HRE and CEAp activates lymphocytes to kill CEA-positive tumor cells specifically

目的:研究5拷贝缺氧反应元件(5HRE)增强子和癌胚抗原启动子(CEAp)联合调控的超抗原中毒性休克综合征毒素-1(TSST-1)在缺氧环境下激活淋巴细胞对CEA阳性的结肠癌细胞株LoVo的杀伤作用。方法:用5HRE和CEAp构成基因表达调控元件,构建出以该元件调控跨膜型超抗原TSST-1-linker-CD80TM(TC)基因靶向表达的真核表达载体。用该载体转染CEA阳性的人结肠癌细胞株LoVo及CEA阴性的人宫颈癌细胞株HeLa,利用G418筛选稳定转染的细胞。用RT-PCR检测TC融合基因的表达。分离健康人外周血淋巴细胞(PBL),用稳定转染TC的细胞裂解物进行PBL刺激实验;将PBL与稳定转染的细胞共培养,行淋巴细胞杀伤实验;MTT法检测TSST-1促PBL增殖和PBL对稳定转染细胞的杀伤效应。结果:成功筛选出稳定转染目的基因的单克隆LoVo细胞和HeLa细胞。RT-PCR证实单克隆LoVo细胞中TC在mRNA水平的表达,且缺氧环境中的表达量更高;单克隆HeLa细胞在常氧和缺氧条件下均无TC的表达。MTT法检测发现,缺氧环境下单克隆LoVo细胞表达的TSST-1能有效激活人PBL增殖,PBL剂量依赖性的抑制表达TSST-1的LoVo细胞的生长(P<0.05);但HeLa细胞和野生型LoVo细胞不能刺激PBL增殖,PBL对其也无抑制作用。结论:5HRE和CEAp双重调控的超抗原TSST-1在体外缺氧环境下可激活人PBL特异杀伤CEA阳性肿瘤细胞。

AIM：To evaluate the inhibitory effect of lymphocytes activated by the superantigen of toxic shock syndrome toxin-1 （TSST-1）, which is regulated synergistically by 5 copies of hypoxia-responsive element （5HRE） and promoter of carcino-embryonic antigen （CEAp）, against the carcino-embryonic antigen （CEA）-positive human colon carcinoma cell line LoVo under hypoxia condition in vitro. METHODS： The eukaryotic expressive vector was constructed with the transmembrane superantigen gene of 5HRE-CEAp-regulated TSST-1-linker-CD80TM, and was transfected into CEA-positive human colon carcinoma cell line LoVo and CEA-negative human cervical carcinoma cell line HeLa by Lipofectamine 2000. Stably transfected cell lines were selected by G418. RT-PCR was employed to examine the expression of TC mRNA. Peripheral blood lymphocytes（PBL） of healthy people were extracted and then activated by the lysates of tumor cells stably transfected with TC. Concurrently, PBL were cultured together with stably transfected tumor cells in order to kill these cells. Then the proliferative effect of TSST-1 on PBL, and the killing effect of PBL against the stably transfected tumor cells were detected by MTT. RESULTS： Monoclonal LoVo and HeLa cells stably transfected with TC were successfully obtained. Expression of TC mRNA in monoclonal LoVo cells under hypoxia condition was significantly higher than those under normoxia condition as confirmed by RT-PCR. Monoclonal HeLa cells did not express TC under either hypoxia condition or normoxia condition. As is shown by MTT assay, TSST-1 expressed by the monoclonal LoVo cells could effectively activate PBL to proliferate under hypoxia condition, resulting in dose-dependent inhibition on the proliferation of LoVo cells that expressed TSST （P〈0.05）. But HeLa cells and wild LoVo cells could not activate PBL to proliferate. PBL could not inhibit proliferation of HeLa cells and wild LoVo cells, either. CONCLUSION： The superantigen of TSST-1 regulated dually by 5HRE and CEAp could activate human PBL to kill CEA-positive tumor cells specifically under hypoxia condition.