Imaging of cancer invasion and metastasis using green fluorescent protein.

The use of green fluorescent protein to fluorescently tag tumour cells has allowed investigators to open the "black box" of metastasis in order to visualise the behaviour of tumour cells in living tissues. Analysis of cells leaving the primary tumour indicates that highly metastatic cells are able to polarise more effectively towards blood vessels while poorly metastatic cells fragment more often when interacting with blood. In addition, there appear to be greater numbers of host immune system cells interacting with metastatic tumours. After arresting in target organs such as the lungs or liver, most tumour cells become dormant or apoptose. A small fraction of the arrested cells form metastases. In some target organs, migration of tumour cells may enhance the ability to form metastases.