Proliferation kinetics of endothelial and tumour cells in three mouse mammary carcinomas

Abstract

An autoradiographic study of 3 corded mouse tumors is reported. The proliferation characteristics of both tumor cells and endothelial cells were studied. The doubling time of these 3 tumors differed by a factor of 2.6, but there was only a small difference in the intermitotic time. All 3 tumros showed a very high cell loss factor (.apprx. 0.80) and the difference in growth rate resulted mainly from differences in the growth fraction. The endothelial cell proliferation rates differed markedly in the 3 tumors, with labeling indices ranging from 18% in the faster tumors to 4.5% in the slowest. The potential doubling times for endothelium, calculated from these values, were much slower than the tumor cell cycle time or the tumor potential doubling time but were 2-4 times faster than the volume doubling time of the tumor. Apparently, the endothelial proliferation rate influences the growth fraction, but similar high cell loss factors can occur in tumors with a 4-fold difference in endothelial cell production rates. Inadequate branching of blood vessels may be at least as important as inadequate production of endothelial cells. It is not possible to determine whether slow tumor cell production evokes a slower endothelial growth or vice versa.