Deneddylation of ribosomal proteins promotes synergy between MLN4924 and chemotherapy to elicit complete therapeutic responses

The neddylation inhibitor MLN4924/Pevonedistat is in clinical trials for multiple cancers. Efficacy is generally attributed to cullin RING ligase (CRL) inhibition, but the contribution of non-CRL targets is unknown. Here, CRISPR screens map MLN4924-monotherapy sensitivity in retinoblastoma to a classic DNA damage induced p53/E2F3/BAX-dependent death effector network, which synergizes with Nutlin3a or Navitoclax. In monotherapy-resistant cells, MLN4924 plus standard-of-care topotecan overcomes resistance, but reduces DNA damage, instead harnessing ribosomal protein nucleolar-expulsion to engage an RPL11/p21/ MYCN/E2F3/p53/BAX synergy network that exhibits extensive cross-regulation. Strikingly, unneddylatable RPL11 substitutes for MLN4924 to perturb nucleolar function and enhance topotecan efficacy. Orthotopic tumors exhibit complete responses while preserving visual function. Moreover, MLN4924 plus melphalan deploy this DNA damage-independent strategy to synergistically kill multiple myeloma cells. Thus, MLN4924 synergizes with standard-of-care drugs to unlock a nucleolar death effector network across cancer types implying broad therapeutic relevance.