表达前列腺特异性膜抗原的DNA疫苗对肿瘤细胞的抑制作用

目的构建表达前列腺特异性膜抗原（PSMA）的DNA疫苗，观察其在体外对肿瘤细胞的免疫攻击和在体内对肿瘤细胞攻击的免疫保护作用。方法通过稳定转染构建表达PSMA的小鼠黑色素瘤细胞系B16-PSMA，将DNA疫苗pCDNA3．1-PSMA通过肌肉注射导入C57BL／6小鼠体内，分离小鼠脾细胞，检测细胞毒性T淋巴细胞（cytotoxic T lymphocytes，CTL）反应。以B16-PSMA细胞攻击免骺小鼠，观察免疫动物的无瘤生存期和肿瘤体积增长情况，评价DNA疫苗的抗肿瘤作用。结果DNA疫苗可诱导小鼠脾淋巴细胞CTL活性，经过免疫后的小鼠成瘤率降低，无瘤生存期延长，肿瘤生长缓慢，肿瘤组织内有较多淋巴细胞浸润，表明产生较强的抗肿瘤反应。结论表达PSMA的DNA疫苗能够诱导小鼠产生特异性免疫反应，对表达PSMA的肿瘤细胞的攻击产生免疫保护作用，为前列腺癌的预防和免疫治疗提供了新的思路。

DNA vaccine expressing PSMA elicits suppresses tumor cells

Objective To construct DNA vaccine expressing PSMA(prostate specific membrane antigen) and to investigate its suppression to tumor cells. Methods An eukaryotic expression vector pCDNA3.1-PSMA encoding full-length PSMA cDNA was constructed, and was introduced into B16 cells to establish a PSMA-expressing murine melanoma B16-PSMA cell line. The C57BL/6 mice were immunized with DNA vaccine pCDNA3.1-PSMA by intramuscular injection. After four dosages of immunizations, splenocytes were isolated and stimulated by mitomycin-treated B16-cells, cytotoxic T lymphocytes(CTL) activity was measured by lactate dehydrogenase(LDH) release method. The immunized C57BL/6 mice were also challenged by transplanting B16-PSMA cells, tumor-free survival time and the growth rate of tumors were recorded to investigate the anti-tumor reaction. Results DNA vaccine expressing PSMA elicited CTL reaction of splenocytes. After DNA vaccine immunization, tumor occurence reduced and tumor-free time was prolonged. Although tumors developed in immunized mice, the growth speed of the tumors was markedly reduced. Histological examination showed that there was infiltration by lymphocytes in tumors from immunized mice, while this infiltration was less prominent in control group. Conclusion DNA vaccine expressing PSMA induced specific cellular immune response and suppressed tumor cells, that may provide a potential alternative in the treatment of carcinoma of prostate.