A model system for studying metastasis using the embryonic chick.

An assay capable of recovering individual viable rodent cells localized in various organs of the chick embryo is described. This assay is based on the differential sensitivity of chick and rodent cells to the cytotoxic drug ouabain. Utilizing this assay, the potential of the chick embryo as a model system for studying metastasis was examined. Several cell lines were characterized in three ways: (a) ability to form local tumors after cell application onto the chorioallantoic membrane; (b) ability to form macro- or microscopic metastasis in the embryo from chorioallantoic membrane tumors; (c) experimental metastatic ability following i.v. injection into chorioallantoic membrane veins. These results were compared with the results obtained from the ouabain-plating assay. We conclude that this assay permits detection of viable metastatic cells even when tumors cannot be detected and helps to overcome the time constraints that have, in the past, limited the usefulness of the chick embryo in modeling metastasis.