The elimination of i. v.-injected tumor cells. Studies with 125IUDR labelled cells in 4 syngeneic murine tumor systems.

We have studied the elimination of radiolabelled (125IUDR) i.v. injected tumor cells. We have used four different murine tumors with different abilities to metastasize and with different metastasis patterns. The elimination of the tumor cells was determined by gamma-countings from different organs. The results were compared with the elimination of heat killed and x-ray sterilized tumor cells. We found a poor correlation between on the one hand the clearance of tumor cells from the blood and distribution of radiolabelled cells and on the other hand the ability of the tumors to metastasize and the metastasis distribution upon i.v. injection. The radioactivity outside the first capillary bed seemed mainly to come from dead cells.