目的: 探讨多次小剂量pEgr-IFN-γ基因 放射治疗对接种B16黑色素瘤小鼠的抑瘤效应及其免疫学机理。方法: 肿瘤局部注射脂质体包裹的重组质粒pEgr-IFN-γ后36 h，接受不同剂量X射线照射，观察各组小鼠照后不同时间肿瘤生长速率和平均存活时间。照后第3天用RT-PCR法检测瘤内IFN-γ转录水平，ELISA法检测小鼠血清中IFN-γ含量，并于照后第15天检测小鼠部分免疫学指标。 结果：照后第9~15天，4次（质粒+5Gy）组小鼠肿瘤生长速率明显低于质粒+20 Gy组，且平均生存时间明显延长；照后第3天质粒+20 Gy组瘤内IFN-γ转录水平明显高于质粒组，照后第1，3天血清中IFN-γ含量明显高于质粒组和对照组，照后第15天脾脏NK细胞毒活性、IL-2和IFN-γ分泌活性均明显高于20 Gy照射组。结论: 多次小剂量基因 放射治疗的抑瘤效应优于单次大剂量基因-放射治疗。基因-放射治疗组可能通过诱导瘤内IFN-γ表达增强，使血液中IFN-γ浓度升高，从而提高荷瘤机体免疫功能和抗肿瘤能力。

Objective：To study the anti-tumor effect of repeated low dose pEgr-IFN-γ gene-radiotherapy in mice bearing melanoma and its immunologic mechanism. Methods:The pEgr-IFN-γ plasmids packed by liposome were injected locally into tumors, and then the tumors was irradiated by X-ray 36 hours later. The tumor growth rate at different time and mean survival period of the mice were observed. The IFN-γ mRNA level in tumors was detected by RT-PCR 3 days after irradiation. The concentration of IFN-γ in serum were detected by ELISA. The immunologic indexes was detected 15 days after irradiation. Results: The tumor growth rate of the mice in gene-radiotherapy group with pEgr-IFN-γ and 5 Gy X-ray irradiation four times were lower significantly than that with pEgr-IFN-γ and 20 Gy X-ray irradiation 9～15 days after irradiation and their mean survival period were longer. The IFN-γ mRNA level in tumors of the mice in gene-radiotherapy group were higher than that in reconstruction plasmids group significantly 3 days after irradiation; The IFN-γ concentration in serum of the mice in gene-radiotherapy group were higher than that in reconstruction plasmids group and control group 1 and 3 days after irradiation; NK cytotoxic activity, IL-2 and IFN-γ secretion activity of the mice in gene-radiotherapy group were higher than that in 20 Gy X-ray irradiation group 15 days after irradiation.Conclusions: The anti-tumor effect of repeated low dose gene-radiotherapy was better than that of high dose gene-radiotherapy for only once. By inducing higher expression of IFN-γ gene in the tumors, pEgr-IFN-γ gene-radiotherapy could increase the concentration of IFN-γ in serum, and therefore the body’s immunologic function and anti tumor ability were enhanced.

国家自然科学基金项目（30170290）资助