Video microscopy of tumor metastasis: using the green fluorescent protein (GFP) gene as a cancer-cell-labeling system

Video microscopy allows dynamic observation of cancer-cell activity in the microcirculation of live animals. However, observation of cancer invasion a nd metastasis in situ has never been successful because of the lack of a te chnique for labeling cancer cells. We report here our success with video mi croscopy of cancer-cell activity, detection of remote metastases and cancer cells endogenously generated using the green fluorescent protein (GFP) gen e as a cell-labeling systemin live animals. As a cell-labeling system, GFP is stable, efficient, and nontoxic, and it is passed on to subsequent gener ations of cells. This pilot experiment has demonstrated the feasibility of direct observation and documentation of tumor growth and tumor invasion as well as the metastatic activities of cancer cells in live animals.