Oncogenes and Tumor Suppressors Extrinsic Apoptosis Is Impeded by Direct Binding of the APL Fusion Protein NPM-RAR to TRADD

A subset of acute promyelocytic leukemia (APL) cases has been characterized by the t(5;17)(q35;q21) translocation variant, which fuses nucleophosmin (NPM) to retinoic acid receptor a (RARA). The resultant NPM-RARfusionproteinblocksmyeloiddifferentiation and leads to a leukemicphenotype similar to that causedby the t(15;17)(q22;q21) PML-RAR fusion. The contribution of the N-terminal 117 amino acids of NPM contained within NPM-RAR has not been well studied. As a molecular chaperone, NPM interacts with a variety of proteins implicated in leukemogenesis. Therefore, a proteomic analysis was conducted to identify novel NPM-RAR– associated proteins. TNF receptor type I–associatedDEATHdomain protein (TRADD)was identified as a relevant binding partner for NPM-RAR. This interaction was validated by coprecipitation and colocalization analysis. Biologic assessment found that NPM-RAR expression impaired TNF-induced signaling through TRADD, blunting TNF-mediated activation of caspase-3 (CASP3) and caspase-8 (CASP8), to ultimately block apoptosis. Implications: This study identifies a novel mechanism through which NPM-RAR affects leukemogenesis. Mol Cancer Res; 12(9); 1283–91. 2014 AACR.