Modeling and Integral X-Ray, Optical, and MRI Visualization of Multiorgan Metastases of Orthotopic 4T1 Breast Carcinoma in BALB/c Mice

A model of highly metastasizing orthotopic allogeneic breast carcinoma was reproduced and standardized in experiments on BALB/c mice. 4T1 cells characterized by high metastatic activity were transfected with red fluorescent protein (RFP) gene or firefly luciferase (Luc2) gene. Unmodified 4T1 cells and modified 4T1-RFP and 4T1-Luc2 cells were subcutaneously injected to mature female mice into the second mammary fat pads. Quantitative evaluation of the primary node and visceral metastases was performed using magnetic-resonance imaging, X-ray and optical tomography. Modification of 4T1 cells with RFP gene considerably reduced their invasive and metastatic potential and led to spontaneous regression of the primary tumor in 20% cases. Modification of 4T1 cells with Luc2 gene had practically no effect on proliferative, invasive, and metastatic characteristics of the tumor and provided the possibility of quantitative analysis of the primary tumor dynamics by the luminescence intensity. The survival median in mice receiving unmodified 4T1 cells and transfected 4T1-RFP and 4Т1-Luc2 cells was 32, 42, and 38 days, respectively. Neither primary node nor tumor metastases accumulated gadolinium-containing contrast agent and Alasens fluorescent tracer. After implantation of 4T1 and 4Т1-Luc2 cells, multiple metastases were more often detected in the lungs, liver, spleen, spine, and regional lymph nodes and less frequently in the brain, which corresponded to metastasizing profile of human breast cancer. The developed model of orthotopic breast carcinoma 4T1 in BALB/c mice with complex detection of multiple organ metastases using X-ray microCT, optical, and MRI can be recommended for preclinical studies of new antitumor preparations.