Notably, many cell lines were sensitive to the p53-MDM2 antagonists (e.g., idasanutlin, SAR405838) except for a group of cell lines, which were consistently resistant to these antagonists (Supplementary Fig. 4b and Supplementary Data 13), among them the KMT2A-AFF1 cell lines (ALL-PO and SEM) with a suspected deregulated p53 pathway which could be due to mutations in TP53 or other dysregulation contributed by the gene fusion50. The gene discussed is MDM2; the disease is acute lymphoblastic leukemia.