Evaluation of the radiotherapy effect on transplanted breast cancer in mice by in vivo fluorescence imaging technique

Abstract

Objective To establish a mouse model of lymph node metastasis of breast cancer cells by luciferase imaging assay, to monitor early process of lymph node metastasis, and to evaluate the effect of X-ray radiation therapy on tumor. Methods The mouse mammary cancer cell line 4T1-Luc expressing luciferase was inoculated subcutaneously into the paw pad of nude mice to establish a model of subcutaneous lymph node metastasis. The lymph node metastasis in nude mice was continuously observed by in vivo fluorescence imaging system, and the nude mice with early lymph node metastasis of breast cancer cells were divided into control group and treatment group randomly. The radiotherapy effect was observed by in vivo fluorescence imaging system and evaluated by the pathological changes of HE staining of tumor tissue. Results A mouse lymph node metastasis model of breast cancer cells was successfully established, and the volume of primary tumor in paw correlated with the fluorescence photon number positively (r=0.958, P<0.001). On the twenty-fourth day after inoculation, the fluorescence photon number in pad tumor and popliteal fossa tumor of treatment group were significantly decreased in comparison with the control group (t=32.58, P<0.05), and the inhibition ratio of radiotherapy on tumor growth approached to 85%. HE staining showed that the apoptosis and necrosis in irradiated tumor was obviously higher than that in control group. Conclusions Bioluminescence imaging technique can be used to evaluate the effect of X-ray on breast cancer suppression and lymph node metastasis in mice. Key words: Luciferase; Breast cancer; Lymph node metastasis; In vivo fluorescence imaging; X-ray