Therapeutic Response to Non-genotoxic Activation of p53 by Nutlin3a Is Driven by PUMA-Mediated Apoptosis in Lymphoma Cells

• Nutlin3a induces p53 activation and target gene expression in mouse lymphoid cells
• Loss of PUMA, but not loss of p21, impairs treatment responses to Nutlin3a
• Malignant lymphoma cells are more sensitive to Nutlin3a than normal lymphocytes
• PUMA is critical for Nutlin3a-induced killing of MYC-driven lymphoma cells

SummaryNutlin3a is a small-molecule antagonist of MDM2 that promotes non-genotoxic activation of p53 through p53 protein stabilization and transactivation of p53 target genes. Nutlin3a is the forerunner of a class of cancer therapeutics that have reached clinical trials. Using transgenic and gene-targeted mouse models lacking the critical p53 target genes, p21, Puma, and Noxa, we found that only loss of PUMA conferred profound protection against Nutlin3a-induced killing in both non-transformed lymphoid cells and Eμ-Myc lymphomas in vitro and in vivo. CRISPR/Cas9-mediated targeting of the PUMA gene rendered human hematopoietic cancer cell lines markedly resistant to Nutlin3a-induced cell death. These results demonstrate that PUMA-mediated apoptosis, but not p21-mediated cell-cycle arrest or senescence, is a critical determinant of the therapeutic response to non-genotoxic p53 activation by Nutlin3a. Importantly, in human cancer, PUMA expression may predict patient responses to treatment with MDM2 antagonists.

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