CASP3 and neoplasm: Evidence of enhanced induction of apoptosis was observed with the combination of the MDM2 inhibitor with MEK inhibitor in our PDX.004 model using immunohistochemical (IHC) analysis for cleaved caspase 3 (average percentage of positive tumor cells: control, 2.6%; selumetinib, 8.2%; KRT-232, 9%; and combination, 18% (combination vs selumetinib, p = 0.003, combination vs KRT-232, p = 0.003; Fig. 5A).