• CC-122 is a novel agent for DLBCL with antitumor and immunomodulatory activity.• CC-122 binds CRBN and degrades Aiolos and Ikaros resulting in a mimicry of IFN signaling and apoptosis in DLBCL.Cereblon (CRBN), a substrate receptor of the Cullin 4 RING E3 ubiquitin ligase complex, is the target of the immunomodulatory drugs lenalidomide and pomalidomide. Recently, it was demonstrated that binding of these drugs to CRBN promotes the ubiquitination and subsequent degradation of 2 common substrates, transcription factors Aiolos and Ikaros.Here we report that CC-122, a new chemical entity termed pleiotropic pathway modifier, binds CRBN and promotes degradation of Aiolos and Ikaros in diffuse large B-cell lymphoma (DLBCL) and T cells in vitro, in vivo, and in patients, resulting in both cell autonomous as well as immunostimulatory effects. In DLBCL cell lines, CC-122-induced degradation or short hairpin RNA-mediated knockdown of Aiolos and Ikaros correlates with increased transcription of interferon (IFN)-stimulated genes independent of IFN-a, -b, and -g production and/or secretion and results in apoptosis in both activated B-cell (ABC) and germinal center B-cell DLBCL cell lines. Our results provide mechanistic insight into the cell-of-origin independent antilymphoma activity of CC-122, in contrast to the ABC subtype selective activity of lenalidomide. (Blood. 2015;126(6):779-789)

SUMMARY Recognition of the proper start codon on mRNAs is essential for protein synthesis, which requires scanning and involves eukaryotic initiation factors (eIFs) eIF1, eIF1A, eIF2 and eIF5. The carboxyl-terminal domain (CTD) of eIF5 stimulates 43S preinitiation complex (PIC) assembly; however, its precise role in scanning and start codon selection has remained unknown. Using nuclear magnetic resonance (NMR) spectroscopy, we identified the binding sites of eIF1 and eIF2β on eIF5-CTD and find that they are partially overlapped. Mutating select eIF5 residues in the common interface specifically disrupts interaction with both factors. By abrogating eIF5-CTD binding to eIF2β, genetic and biochemical evidence indicate that these eIF5-CTD mutations impair start codon recognition and impede eIF1 release from the PIC. This study provides mechanistic insight into the novel role of eIF5-CTD’s dynamic interplay with eIF1 and eIF2β in switching PICs from an open to closed state at start codons.

Recent discoveries suggest that the critical events leading to the anti-proliferative activity of the IMiD immunomodulatory agents lenalidomide and pomalidomide in multiple myeloma (MM) cells are initiated by Cereblon-dependent ubiquitination and proteasomal degradation of substrate proteins Ikaros (IKZF1) and Aiolos (IKZF3). By performing kinetic analyses, we found that the downregulation or proteasomal degradation of Ikaros and Aiolos led to specific and sequential downregulation of c-Myc followed by IRF4 and subsequent growth inhibition and apoptosis. Notably, to ensure growth inhibition and cell death, sustained downregulation of Ikaros and Aiolos, c-Myc or IRF4 expression was required. In addition, we found that the half-maximal rate, rather than the final extent of Ikaros and Aiolos degradation, correlated to the relative efficacy of growth inhibition by lenalidomide or pomalidomide. Finally, we observed that all four transcription factors were elevated in primary MM samples compared with normal plasma cells. Taken together, our results suggest a functional link between Ikaros and Aiolos, and the pathological dysregulation of c-Myc and IRF4, and provide a new mechanistic understanding of the relative efficacy of lenalidomide and pomalidomide based on the kinetics of substrate degradation and downregulation of their downstream targets.

Purpose: Randomized, multicenter, open-label, phase 2/3 trial investigating lenalidomide versus investigator's choice (IC) in relapsed/refractory diffuse large B-cell lymphoma (DLBCL).Experimental Design: Patients with DLBCL who received 2 prior therapies were stratified by DLBCL subtype [germinal center B-cell (GCB) vs. non-GCB; determined by immunohistochemistry (IHC)] and then randomized 1:1 to lenalidomide (25 mg/day, 21 days of 28-day cycle) or IC (gemcitabine, rituximab, etoposide, or oxaliplatin). Crossover to lenalidomide was permitted for ICtreated patients with radiologically confirmed progressive disease. The primary endpoint was overall response rate (ORR). Progression-free survival (PFS), overall survival, and subtype analysis [GCB vs. activated B-cell (ABC)] using gene expression profiling (GEP) were exploratory endpoints.Results: Stage 1: 102 DLBCL patients (by IHC: non-GCB, n ¼ 54; GCB, n ¼ 48) received 1 dose of lenalidomide or IC. Hematologic treatment-emergent adverse events with lenalidomide versus IC included neutropenia (42.6%; 36.4%), anemia (33.3%; 47.3%), thrombocytopenia (24.1%; 43.6%), and leukopenia (5.6%; 12.7%), respectively. Overall, lenalidomidetreated patients had an ORR of 27.5% versus 11.8% in IC (ORRs were similar regardless of IHC-defined DLBCL subtype). Median PFS was increased in patients receiving lenalidomide (13.6 weeks) versus IC (7.9 weeks; P ¼ 0.041), with greater improvements in non-GCB patients (15.1 vs. 7.1 weeks, respectively; P ¼ 0.021) compared with GCB (10.1 vs. 9.0 weeks, respectively; P ¼ 0.550).Conclusions: The clinical benefit of lenalidomide monotherapy in DLBCL patients was more evident in the non-GCB subtype. Exploratory analyses suggest that this preferential benefit was more pronounced in the GEP-defined ABC population, demonstrating a need for additional studies of lenalidomide in DLBCL using GEP subtyping. Clin Cancer Res; 23(15); 4127-37. Ó2017 AACR.

In a breast tumor xenograft model, the MCT-1 oncogene increases the in vivo tumorgenicity of MCF7 cells by promoting angiogenesis and inhibiting apoptosis. Increases in the tumor microvascular density are accompanied by a strong reduction in the levels of the angiogenesis inhibitor thrombospondin-1 (TSP1), but the mechanisms underlying this process are unknown. We show that TSP1 expression is controlled, at least in part, by post-transcriptional events. Using RNA interference to knock down the expression of the RNA-binding protein HuR in MCF7 cells as well as HuR overexpression, we demonstrate that HuR plays an important role in translation of the TSP1 mRNA. Furthermore, employing the RIP-Chip assay yielded 595 transcripts with significantly altered binding to HuR in the more tumorigenic breast cancer clones compared with the weakly tumorigenic clones. These mRNAs clustered in several pathways implicated in the transformed phenotype, such as the RAS pathway (involved in mitogenesis), the PI3K pathway (evasion of apoptosis) and pathways mediating angiogenesis and the cellular response to hypoxia. These findings demonstrate for the first time that global changes in HuR-bound mRNAs are implicated in the evolution to a more tumorigenic phenotype in an in vivo tumor model and underscore the role of global mRNA-protein interactions toward tumor progression.