RESUMO
Objective To evaluate the antitumor effects of interferon (IFN)γ-endostatin based gene radiotherapy in a metastatic breast tumor model of mice, and to elucidate the possible mechanisms involved. Methods Murine mammary adenocarcinoma 4T1 cells transfected with pEgr-IFN-γ and pEgrendostatin plasmids were irradiated with 2-20 Gy of X-rays. IFN-γ and endostatin levels in the culture supernatants were measured. Female BALB/c mice were inoculated with 1 × 105 of 4T1 cells by mammary fat pad injection, and divided randomly into control, empty vector, gene therapy (pEgr-IFN-γ and pEgrendostatin), radiotherapy, and combined gene-radiotherapy groups. Tumor/body weight ratio, lung metastases, and survival of the tumor-bearing mice were observed. Splenic cytotoxic T-lymphocyte (CTL)and natural killer (NK) cell activity and intratumor microvessel density were also assessed. Results Irradiation significantly enhanced the section of IFN-γ and endostatin from the transfected 4T1 cells.Compared with gene therapy or radiotherapy alone, combined gene-radiotherapy resulted in the maximal attenuation in tumor growth rate, lung metastases and increased survival. The activities of CTL and NK cells were significantly enhanced and intratumor microvessel density reduced ( t = 2. 120-22.140, P ＜ 0.05 ).Conclusions IFN-γ-endostatin-based gene-radiotherapy could provide a potential antitumor effect in a murine metastatic breast tumor model, which may be related to IFN-γ-stimulated CTL and NK cell activation, and endostatin-induced antiangiogenic activity. Gene-radiotherapy could serve as a neoadjuvant therapy for the locally advanced breast cancer.