title: Drug resistance to inhibitors of the human double minute-2 E3 ligase is mediated by point mutations of p53, but can be overcome with the p53 targeting agent RITA.
abstract: The human double minute (HDM)-2 E3 ubiquitin ligase plays a key role in p53 turnover and has been validated preclinically as a target in multiple myeloma (MM) and mantle cell lymphoma (MCL). HDM-2 inhibitors are entering clinical trials, and we therefore sought to understand potential mechanisms of resistance in lymphoid models. Wild-type p53 H929 MM and Granta-519 MCL cells resistant to MI-63 or Nutlin were generated by exposing them to increasing drug concentrations. MI-63-resistant H929 and Granta-519 cells were resistant to Nutlin, whereas Nutlin-resistant cells displayed cross-resistance to MI-63. These cells also showed cross-resistance to bortezomib, doxorubicin, cisplatin, and melphalan, but remained sensitive to the small molecule inhibitor RITA (reactivation of p53 and induction of tumor cell apoptosis). HDM-2 inhibitor-resistant cells harbored increased p53 levels, but neither genotoxic nor nongenotoxic approaches to activate p53 induced HDM-2 or p21. Resequencing revealed wild-type HDM-2, but mutations were found in the p53 DNA binding and dimerization domains. In resistant cells, RITA induced a G(2)-M arrest, upregulation of p53 targets HDM-2, PUMA, and NOXA, and PARP cleavage. Combination regimens with RITA and MI-63 resulted in enhanced cell death compared with RITA alone. These findings support the possibility that p53 mutation could be a primary mechanism of acquired resistance to HDM-2 inhibitors in MCL and MM. Furthermore, they suggest that simultaneous restoration of p53 function and HDM-2 inhibition is a rational strategy for clinical translation.
authors.affiliation: Department of Lymphoma and Myeloma, The University of Texas M.D. Anderson Cancer Center, 7455 Fannin St, Unit 403, Houston, TX 77054, USA. rjones@mdanderson.org
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Jones
authors.forename: Chad C
authors.initials: CC
authors.lastname: Bjorklund
authors.forename: Veerabhadran
authors.initials: V
authors.lastname: Baladandayuthapani
authors.forename: Deborah J
authors.initials: DJ
authors.lastname: Kuhn
authors.forename: Robert Z
authors.initials: RZ
authors.lastname: Orlowski
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D004354:Drug Screening Assays, Antitumor; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology; D005663:Furans / Q000737:chemistry / Q000494:pharmacology*; D016195:G2 Phase / Q000187:drug effects; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D017354:Point Mutation / Q000235:genetics*; D051736:Proto-Oncogene Proteins c-mdm2 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics*; D044767:Ubiquitin-Protein Ligases / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D050759:Cyclin-Dependent Kinase Inhibitor p21; D004791:Enzyme Inhibitors; D005663:Furans; D007093:Imidazoles; C118989:NSC 652287; D010879:Piperazines; D016159:Tumor Suppressor Protein p53; C482203:nutlin 1; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; D044767:Ubiquitin-Protein Ligases