敲低吲哚胺2,3双加氧酶2基因抑制荷黑素瘤小鼠肿瘤生长并增强其免疫功能

Knockdown of indoleamine 2,3-dioxygenase 2 ( IDO2) gene inhibits tumor growth and enhances immune function in mice bearing melanoma

目的以吲哚胺2,3双加氧酶2(IDO2)作为治疗靶标,研究IDO2基因表达在肿瘤治疗中的作用及其对免疫应答的影响。方法采用B16-BL6细胞株构建小鼠黑素瘤种植模型,以携带IDO2小干扰RNA的质粒(IDO2-shRNA)及对照组质粒(scramble-shRNA)尾静脉高压注射法治疗小鼠黑素瘤;游标卡尺测量肿瘤大小;流式细胞术检测各组引流淋巴结内调节性T细胞(Treg)百分比、T细胞凋亡百分比,以及脾脏内树突状细胞(DC)表面共刺激分子CD80、CD86表达情况;乳酸脱氢酶法检测CD8+T淋巴细胞杀伤肿瘤细胞的能力;ELISA检测血清内肿瘤坏死因子α(TNF-α)、γ干扰素(IFN-γ)的水平。结果 IDO2-shRNA治疗组肿瘤的形成时间较晚,肿瘤的生长速度缓慢,离体肿瘤质量明显减少;IDO2-shRNA治疗组引流淋巴结内的Treg减少,T细胞凋亡降低,脾脏DC表面共刺激分子CD80、CD86明显增加;CD8+T细胞杀伤B16-BL6的能力增强,血清内TNF-α、IFN-γ表达水平升高。结论敲低荷瘤小鼠体内IDO2可抑制黑素瘤生长,提高机体的抗肿瘤免疫反应。

Objective To study the role of indoleamine 2,3-dioxygenase 2（ IDO2） in anti-tumor therapy and its effect on the immune response when using IDO2 as therapeutic target. Methods B16-BL6 cells were used to construct mouse xenografted melanoma model. IDO2-shRNA that contained IDO2-siRNA or control shRNA（ scrambled-shRNA） was injected hydrodynamically via the tail vein to treat melanoma. The tumor size was measured by vernier caliper. Flow cytometry was performed to analyze the percentage of regulatory T cells（ Tregs）,T cell apoptosis rate in draining lymph nodes and the expressions of co-stimulatory molecules on splenic dendritic cells（ DCs） from different treatment groups. The lactate dehydrogenase（ LDH） assay was used to determine the CD8＋cytotoxic T lymphocyte（ CTL） activity. The serum levels of tumor necrosis factor α（ TNF-α） and interferon γ（ IFN-γ） were detected by ELISA. Results In the IDO2-shRNA treated group,the tumor formation time was delayed,tumor grew slowly,and excised tumor mass was significantly reduced. IDO2-shRNA treatment also decreased the percentage of Tregs and T cell apoptosis in draining lymph nodes and increased the expressions of co-stimulatory molecules CD80 and CD86 on splenic DCs. The capacity of CD8＋T cells to kill B16-BL6 cells was enhanced and the serum levels of TNF-α and IFN-γ were upregulated. Conclusion Silencing IDO2 can effectively inhibit the growth of melanoma and improve the anti-tumor immune response in vivo.