hsstr2基因转染肿瘤细胞的受体显像研究

Experimental study on radionuclide imaging of receptor-hsstr2 gene transfected tumor cells

目的将人生长抑素受体2亚型(hsstr2)基因转染至该受体表达阴性的肿瘤细胞,并进行该受体介导的肿瘤显像。方法应用逆转录-聚合酶链反应(RT-PCR)方法获得hsstr2基因并构建真核表达载体,将hsstr2基因转染至肺腺癌A549细胞系(hsstr2表达阴性),用RT—PCR及流式细胞术检测受体表达情况;采用高表达细胞株进行该受体体外结合特性研究,建立裸鼠肿瘤模型,探讨该受体介导的肿瘤显像方法。结果获得经测序完全正确的hsstr2基因,RT-PCR及流式细胞术鉴定选取高表达的细胞株,体外结合实验测得平衡解离常数Kd=5.65×10-10mol/L,最大结合容量Bmax=2.01×104结合位点/细胞,半数抑制浓度IC50=1.88×10-9mol/L。裸鼠肿瘤模型显像示,静脉注射显像剂99Tcm-RC-160后0.5-1 h肿瘤显影明显,24 h后肿瘤部位第2次显影。结论将hsstr2转染至该受体表达阴性的肿瘤细胞并进行受体介导的肿瘤显像是可行的,适宜显像时间为0.5-1 h。

Objective To transfect human somatostatin receptor type 2 （hsstr2） gene to negative gene expressed tumor cell line, and to study receptor mediated imaging in tumor bearing mice. Methods Reverse transcription-polymerase chain reaction （RT-PCR） was used to amplify hsstr2 cDNA from total RNAs prepared from human embryonic kidney （HEK） 293 cells, an enkaryotic expression vector of hsstr2 was constructed, and then infected by human lung adenocarcinoma A549 cells. In vitro radio receptor binding characteristics, A549 tumors bearing nude mice models and tumor scintigraphy were investigated. Results Hsstr2 gene was successfully cloned, the expression of SSTR2 in those clones was confirmed by RT-PCR and flow cytometry. Seatchard analysis of ^125I-RC-160 and tumor cell revealed that Kd =5.65 × 10^-10mol/L,Bmax = 2.01 × 10^4/cell. In competitive binding assay, IC50 = 1.88 × 10^-9 mol/L. Tumor lesions was visualized clearly at 0.5 - 1 h after injection of ^99Tc^m-RC-160. The image could still showed at 24 h. Conclusions It is feasible to transfer hsstr2 to negative gene expressed tumor cell line and visualize it through receptormediated scintigraphy. The optimal time for scintigraphy is 0.5 - 1 h postinjection.