Caspase-2-dependent tumor suppression does not depend on the scaffold protein Raidd

The receptor-interacting protein-associated ICH-1/CED-3 homologous protein with a death domain (Raidd) functions as a dual adaptor protein due to its bipartite nature, and is therefore thought to be a constituent of different multiprotein complexes including the PIDDosome, where it connects the cell death-related protease, Caspase-2, with the p53-induced protein with a death domain 1 (Pidd1). As such, Raidd has been implicated in DNA-damage-induced apoptosis as well as in tumor suppression, the latter based on its role as a direct activator of Caspase-2, known to delay lymphomagenesis caused by overexpression of c-Myc or loss of ATM kinase. As loss of Caspase-2 leads to an acceleration of tumor onset in the Eµ-Myc mouse model we set out to interrogate the role of Raidd in this process in more detail. Our data obtained analyzing Eµ-Myc/Raidd-/- mice indicate that Raidd is unable to protect from c-MYC-driven lymphomagenesis. Similarly, we failed to observe an effect of Raidd-deficiency on thymic lymphomagenesis induced by y-irradiation or fibrosarcoma development driven by 3-methylcholanthrene. The role of Caspase-2 as a tumor suppressor can therefore be uncoupled from its ability to interact and auto-activate upon binding to Raidd. Further, we provide supportive evidence that the tumor suppressive role of Caspase-2 is related to maintaining genomic integrity and allowing efficient p53-mediated signaling. Overall, our findings suggest that Raidd, although described to be the key-adapter allowing activation of the tumor suppressor Caspase-2, fails to suppress tumorigenesis in vivo. Comparison of preB cells (Eµ-Myc transgene) lacking Raidd or Caspase-2 against wt cells.