BACKGROUNDGene-radiotherapy, the combination of gene therapy and radiation therapy, is a new paradigm for cancer treatment. To enhance anti-tumor effect of gene-radiotherapy, in this study we construct a radiation-inducible dual-gene co-expression vector pEgr-interferon (IFN)-gamma-endostatin and studied the anti-tumor effect of pEgr-IFN-gamma-endostatin gene-radiotherapy in mice bearing Lewis lung carcinoma and its mechanism.

METHODSGene recombinant technique was used to construct dual-gene co-expression plasmid pEgr-IFN-gamma-endostatin, and single-gene expression plasmid pEgr-IFN-gamma and pEgr-endostatin. The plasmids packed by liposome were injected locally into the tumors of the mice, and the tumors were irradiated with 5 Gy X-ray 36 hours later. The tumor growth rate at different time and mean survival period of the mice were observed. Cytotoxic activity of splenic cytotoxic T-lymphocyte (CTL), natural killer (NK) cell and tumor necrosis factor (TNF)-alpha secretion activity of peritoneal macrophages of the mice in various groups were evaluated 15 days after irradiation. The intratumor micro-vessel density was evaluated by immunohistochemical staining 10 days after irradiation.

RESULTSThe tumor growth rate of the mice in dual-gene-radiotherapy group was significantly lower than those in control group, 5 Gy group and single-gene-radiotherapy group at different time after gene-radiotherapy, and the mean survival period of which was longer. Cytotoxic activity of splenic CTL, NK and TNF-alpha secretion activity of peritoneal macrophages of the mice in dual-gene-radiotherapy group were significantly higher than those in control group, 5 Gy X-ray irradiation group and pEgr-endostatin gene-radiotherapy group 15 days after irradiation. The intratumor micro-vessel density of the mice in dual-gene-radiotherapy group was significantly lower than those in control group, 5 Gy X-ray irradiation group and pEgr-IFN-gammagene-radiotherapy group.

CONCLUSIONThe anti-tumor effect of dual-gene-radiotherapy was significantly better than that of single-gene-radiotherapy by combining the enhancement of anti-tumor immunologic function induced by IFN-gamma with the anti-angiogenesis function of endostatin.