CASP3 and melanoma: Only modest induction of apoptosis occurred with 10 nM-1 μM concentrations of palbociclib in B16 melanoma cells, but 10 μM palbociclib induced a significant amount of apoptosis (Figure 1D). PF-07104091 did not significantly affect caspase 3/7 activity in B16F10 melanoma cells (Figure 1E).