CASP3 and neoplasm: The number of the proliferation marker Ki67-positive cells, but not that of the apoptosis marker cleaved caspase 3-positive cells, was higher in tumours resulting from the co-injection of MDA-MB-231 cells with WT MEFs than in tumours resulting from the co-injection with Mint3 KO MEFs and from MDA-MB-231 cells alone (Figures 1g and h).