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Pharmacological disruption of the Notch transcription factor complex

ABSTRACT: Notch pathway signaling is implicated in several human cancers. Aberrant activation and mutations of Notch signaling components are linked to tumor initiation, maintenance and resistance to cancer therapy. Several strategies, such as monoclonal antibodies (MAbs) against Notch ligands and receptors, as well as small molecule -secretase inhibitors (GSIs), have been developed to interfere with Notch receptor activation at proximal points in the pathway. However, the use of drug-like small molecules to target the downstream mediators of Notch signaling, the Notch transcription activation complex, remains largely unexplored. Using a Notch signaling dependent co-culture system, we developed a high-throughput small molecule screening assay. Herein we report the discovery of an orally active small molecule inhibitor (termed CB-103) of the Notch transcription activation complex. We show that CB-103 inhibits Notch signaling in primary human T-ALL and other Notch-dependent human tumor cell lines, and concomitantly induces cell cycle arrest, thereby impairing proliferation. Notably, CB-103 has the ability to downregulate Notch signaling in GSI-resistant human tumor cell lines that harbor chromosomal translocations and rearrangements in Notch genes. CB-103 mimics Notch loss-of-function phenotypes in flies and mice, retarding tumor growth in xenograft models of breast cancer and patient-derived xenograft models of human leukemia, notably without causing the frequently observed dose-limiting intestinal toxicity induced by other Notch inhibitors. In summary, we describe a pharmacological strategy to interfere with Notch signaling by disrupting the transcriptional regulatory complex it assembles, with therapeutic potential for the treatment of human tumors.

ORGANISM(S): Homo sapiens

PROVIDER: GSE148228 | GEO | 2020/12/19

REPOSITORIES: GEO

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Project description:Notch signaling is frequently hyperactivated in breast cancer, but how the enhanced signaling contributes to the tumor process is less well understood. In this report, we identify the proinflammatory cytokine interleukin-6 (IL-6) as a novel Notch target in breast tumor cells. Enhanced Notch signaling upregulated IL-6 expression at the transcriptional level, leading to activation of autocrine and paracrine JAK/STAT signaling. IL-6 upregulation was mediated by non-canonical Notch signaling, as it could be effectuated by a cytoplasmically localized Notch intracellular domain and was independent on the DNA-binding protein CSL. Instead, Notch-mediated IL-6 upregulation was controlled by two other factors: IKKÎ², a protein in the NF-kB signaling cascade, and p53. Activation of IL-6 by Notch required IKKÎ² function, but interestingly, did not engage canonical NF-ÎºB signaling, in contrast to IL-6 activation by inflammatory agents such as tumor necrosis factor, which requires canonical NF-ÎºB signaling. With regard to p53 status, IL-6 expression was upregulated by Notch when p53 was mutated or lost, but restoring wildtype 53 into p53-mutated or -deficient cells abrogated the IL-6 upregulation. Furthermore, Notch-induced genome-wide transcriptomes from p53 wildtype and -mutated breast tumor cell lines differed extensively, and in a subset of genes upregulated by Notch in a p53-mutant cell line, upregulation was reduced by wildtype p53. In conclusion, we identify IL-6 as a novel non-canonical Notch target gene, and reveal roles for p53 and IKKÎ² in non-canonical Notch signaling in breast cancer and in the generation of cell context-dependent diversity in the Notch signaling output. 30 microarray samples consisting of MCF7 (ER+, wild-type p53, luminal type B breast cancer) and MDA-MB-231 (ER-, mutated p53, basal breast cancer) cells cultured on immobilized 1 Î¼g/ml JAGGED1-Fc or 1 Î¼g/ml DLL4-Fc or 1 Î¼g/ml Fc control with or without 5 Î¼M DAPT for 6 hours in 3 biological replicates.

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Pharmacological disruption of the Notch transcription factor complex

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