MDM2 and myelodysplastic syndrome: Given the fact that MDM2 expression was downregulated in all four HMA-resistant sublines in this study and that P39 and Kasumi-1 did not harbor chromosome 5q deletion, both the tumor-suppressive role independent of 5q deletion and the conventional proto-oncogenic role of MDM2 observed in del(5q) MDS should be considered [53].