Death and Metastatic Distribution of Tumor Cells in Mice Monitored With 125I-Iododeoxyuridine 2

Tumor cells (L1210 and Ehrlich ascites) were labeled with 125I-iododeoxyuridine and inoculated into nonradioactive hosts. The fate of the labeled cells and their progeny was monitored at daily intervals by measuring the 125I retention of individual live mice in a well-type crystal scintillation counter. The excretion of 125I from the test animals was linked to in vivo death and breakdown of tumor cells. The fractional rate of tumor cell death depended on the route of implantation, i.e., on the location of tumor cells within the host. After intraperitoneal inoculation of labeled tumor cells, the rate of cell death was about 15% per day. Subcutaneous and intramuscular implantation produced much higher death rates (20–40%/day), and up to 55% of the cells died each day after intravenous inoculation. When prekilled tumor cells were inoculated into mice, 125I was rapidly excreted from the test animals. The anatomical distribution of tumor cells also varied with the route of their administration. After intraperitoneal implantation, large numbers of tumor cells migrated from the peritoneal cavity. Tumor cells inoculated at extraperitoneal sites did not invade the peritoneal cavity. Liver and spleen were major recipients of migrating tumor cells, especially after intravenous inoculation.