A study on the establishment and growth of tumor metastases with tritiated thymidine.

Abstract

Summary The fate of intravenously injected Ehrlich ascites tumor cells, lodging in the lungs, and their subsequent growth into grossly visible metastases have been studied in CAF 1 mice, with tritiated thymidine used to label the tumor cells synthesizing deoxyribonucleic acid (DNA). The animals were given tritiated thymidine either in a single dose at varying intervals or in multiple doses at a given interval after intravenous injection of tumor cells. Autoradiographic and radiochemical investigations of the lungs of these animals indicated the following: ( a ) only very few of the injected tumor cells survived at the site of arrest in the capillaries of the lungs; ( b ) the surviving tumor cells began to synthesize DNA within 2 hours after lodging in the lung capillaries; ( c ) after the 3d day from injection, the tumor cells in the lungs grew at a constant rate with 100 per cent of the cells dividing every 18–20 hours; ( d ) such a type of growth is described by an exponential growth curve. These findings are discussed in the light of our knowledge on the establishment and growth of tumor metastases.