In vivo tumour-cell proliferation after adriamycin treatment.

Adriamycin (10 mg/kg) administered s.c. to male ACI rats bearing Hepatoma H-4-II-E caused a 9-day delay in tumour growth but no changes in the clonogenic fraction of the tumour were detectable by in vitro assay at any time after treatment. There is no significant decrease in the yield of cells on enzymatic dissociation of the tumour nor a reduction in mg DNA/g tumour that might indicate a decrease in tumour cellularity. Mitotic and labelling indices and [3H]dT uptake into DNA remain essentially unchanged, relative to age-equivalent controls, but are slightly lower than in controls of equal weight. The reliability of the clonogenic assay and possible mechanisms by which Adriamycin delays tumour growth are discussed.