The spread of cancer cells from a primary tumor to form metastasis at distant sites is a
complex multistep process. The cancer cell proteins and plasma membrane proteins in
particular involved in this process are poorly defined, and a study of the very early events of
the metastatic process using clinical samples or in vitro assays is not feasible. We have used
a unique model system consisting of two isogenic human breast cancer cell lines that are
equally tumorigenic in mice; but although one gives rise to metastasis, the other …