A cytokinetic model for heterogeneous mammalian cell populations. III. Tritiated thymidine studies: Correlations among multiple kinetic parameters in human tumors

A computer model for the simulation of radioautographic studies in growing mammalian cell populations was used to study multiple tritiated thymidine (³HTdR) associated parameters in model populations whose properties are comparable to those found in human tumors. Several different DNA synthesis rate patterns are distinguishable, designated type I, intermediate, and type II. Correlations among percent labelled mitosis (PLM) curves, interphase cell labelling patterns, and continuous ³HTdR labelling studies suggest a type I pattern in human breast cancer, an intermediate pattern in human melanoma, and a type II pattern in human adult leukemia. Detailed simulation studies were carried out in human adult acute leukemia and human melanoma. It was possible to fit all available kinetic data in leukemia and melanoma, both with respect to low threshold data, and with respect to radioautographic labelling intensity, provided that simulated experimental conditions and simulated radioautographic conditions corresponded to those actually employed. Kinetic differences between leukemia and melanoma were demonstrated which are in keeping with the natural histories and clinical drug response behavior of these two malignancies.