Establishment of a Bioluminescent and Fluorescent MDA-MB-231 Subclone for Real-time In Vivo Imaging of the Metastatic Process

Breast cancer is the most common cancer in women. Although advances in diagnostic imaging for early detection, surgical techniques and chemotherapy have improved overall survival, the prognosis of patients with metastatic breast cancer remains poor. The common metastatic sites of breast cancer are lymph nodes, liver, lungs, bones, and brain. Hematogenous metastasis is a complex, multi-step process by which primary tumor cells invade adjacent tissues, intravasate, transfer to other organs, extravasate, and finally develop secondary tumors. Understanding cancer cell dynamics in the metastatic process is important to develop new therapeutic strategies. However, it is difficult to reproduce the complex steps in vitro precisely. In this study, we developed a real-time in vivo imaging system for tracking breast cancer cells in the metastasis process. We established a subclone of human breast cancer cell line MDA-MB-231 stably expressing luciferase and green fluorescent protein ZsGreen-1 (231-luc-ZsGreen). The 231-luc-ZsGreen cells developed metastases in the brain and bones after inoculation into the left cardiac ventricle of nude mice. Bioluminescent signals of luciferase were detected from three days after inoculation and allowed for whole-body monitoring of metastatic sites. By two-photon microscopy, fluorescence signals of ZsGreen-1 allowed to visualize a single tumor cell moving in capillaries and extravasating into the brain parenchyma in real time. Strong fluorescence signals remained even after formalin fixation and could easily detect micrometastases on tissue sections. This new metastasis model of breast cancer could be a powerful tool to study the metastatic process in vivo.第36回日本分子生物学会年