New Method to Quantitate Clonogenic Tumor Cells in the Blood Circulation of Mice¹

A bioassay method to quantitate “clonogenic” tumor cells released into the blood circulation from murine primary tumors is described. The method uses preirradiation of the thorax of the tumor-bearing mice, followed 22 hr later by preparation and culture of a lung cell suspension which contains filtered tumor cells from the blood. The malignant cells form colonies. Our results indicate that the number of “clonogenic” tumor cells in the blood circulation can be quantitated efficiently using only a few mice. This is a major advantage, since previous studies were limited by small amounts of available blood and somewhat uncertain techniques for identification of blood-borne tumor cells. The present method allows us to evaluate “clonogenic” tumor cells and tumorigenicity, which microscopical identification of tumor cells after filtration of a small amount of blood does not permit.