Study of in vivo tumor state and response to therapy by analysis of DNA distribution

The growth characteristics of an in vivo tumor model were studied. This tumor offers an intermediate system useful for the study of tumor cells in the intact animal, but does not have the complexities of solid tumors. DNA distribution was correlated with macromolecular DNA synthesis. Mechlorethamine, BCNU, radiation, and hydroxyurea were studied and produced perturbation in stationary phase-cell kinetics. There was a redistribution of cell ages consistent with induced cycling activity with most, but not all, of the above agents. This indicated a recruitment from a stationary phase by cancer therapeutic agents, although subsequent cell-cycle traverse may also be greatly perturbed. A number of considerations important to the interpretation of this type of data are discussed.