These cell lines were derived from FAB subtype M4 patients (representing ∼25% of AML) and express wild-type PARP144 and TP53. 45Ara-C treatment of OCI-AML2 and OCI-AML3 cells for 24 h caused phosphatidylserine exposure to the surfaces of both cell lines without loss of membrane integrity (Figure 1A). This evidence concerns the gene TP53 and acute myeloid leukemia.