The combined anti-proliferative effect of PJ, ATRA and 9-<i>cis</i> is additive.

<p>HSCs were plated in 96 well plates. After 24 hrs, the medium was changed to starvation medium (DMEM with 0.5% FCS) overnight. HSCs were incubated for 24 hrs with 30 ng/ml PDGF, PJ, ATRA and 9-<i>cis</i> at doses of 10^-5-10^-4M. Cells were quantified by crystal violet staining. The inhibition of cell proliferation was expressed as % inhibition and calculated according to the following equation: Inhibitory effect (%) = 100 X (OD_control – OD_treatment) / (OD_control – OD_bl). The interaction is synergistic when the experimentally observed effect is larger than the calculated additive effect. When the experimentally observed effect is smaller the calculated additive effect, the interaction is antagonistic, and the interaction is additive when there is no difference between the two effects. Histogram showing average ±SE of densitometry results from 3 independent experiments.