TP53mutations and drug sensitivity in acute myeloid leukaemia cells with acquired MDM2 inhibitor resistance

AbstractBackground:MDM2 inhibitors are under investigation for the treatment of acute myeloid leukaemia (AML) patients in phase III clinical trials. To study resistance formation to MDM2 inhibitors in AML cells, we here established 45 sub-lines of the AMLTP53wild-type cell lines MV4-11 (15 sub-lines), OCI-AML-2 (10 sub-lines), OCI-AML-3 (12 sub-lines), and SIG-M5 (8 sub-lines) with resistance to the MDM2 inhibitor nutlin-3.Methods: Nutlin-3-resistant sub-lines were established by continuous exposure to stepwise increasing drug concentrations. TheTP53status was determined by next generation sequencing, cell viability was measured by MTT assay, and p53 was depleted using lentiviral vectors encoding shRNA.Results:All MV4-11 sub-lines harboured the same R248W mutation and all OCI-AML-2 sub-lines the same Y220C mutation, indicating the selection of pre-existingTP53-mutant subpopulations. In concordance, rare alleles harbouring the respective mutations could be detected in the parental MV4-11 and OCI-AML-2 cell lines. The OCI-AML-3 and SIG-M5 sub-lines were characterised by varyingTP53mutations or wild typeTP53, indicating the induction ofde novo TP53mutations. Doxorubicin, etoposide, gemcitabine, cytarabine, and fludarabine resistance profiles revealed a noticeable heterogeneity among the sub-lines even of the same parental cell lines. Loss-of-p53 function was not generally associated with decreased sensitivity to cytotoxic drugs.Conclusion:We introduce a substantial set of models of acquired MDM2 inhibitor resistance in AML. MDM2 inhibitors select, in dependence on the nature of a given AML cell population, pre-existingTP53-mutant subpopulations or inducede novo TP53mutations. Although loss-of-p53 function has been associated with chemoresistance in AML, nutlin-3-adapted sub-lines displayed in the majority of experiments similar or increased drug sensitivity compared to the respective parental cells. Hence, chemotherapy may remain an option for AML patients after MDM2 inhibitor therapy failure. Even sub-lines of the same parental cancer cell line displayed considerable heterogeneity in their response to other anti-cancer drugs, indicating the need for the detailed understanding and monitoring of the evolutionary processes in cancer cell populations in response to therapy as part of future individualised treatment protocols.