Development of a Novel B-Cell Lymphoma 6 (BCL6) PROTAC To Provide Insight into Small Molecule Targeting of BCL6

McCoull, William; Cheung, Tony; Anderson, Erica; Barton, Peter; Burgess, Jonathan; Byth, Kate; Cao, Qing; Castaldi, M. Paola; Chen, H.; Chiarparin, Elisabetta; Carbajo, Rodrigo J.; Code, Erin; Cowan, Suzanna; Davey, Paul; Ferguson, Andrew D.; Fillery, Shaun; Fuller, Nathan O.; Gao, Ning; Hargreaves, David; Howard, Martin; Hu, Jun; Kawatkar, Aarti; Kemmitt, Paul D.; Leo, Elisabetta; Molina, Daniel Martinez; O’Connell, Nichole; Petteruti, Philip; Rasmusson, Tim; Raubo, Piotr; Rawlins, Philip; Ricchiuto, Piero; Robb, Graeme R.; Schenone, Monica; Waring, Mike J.; Zinda, Michael; Fawell, Stephen E.; Wilson, David M.

doi:10.1021/acschembio.8b00698

Cited by 115 publications

(112 citation statements)

References 40 publications

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“…Further approaches to use BCL6 small molecule inhibitors as target binding ligand of proteolysis targeting chimeras (PROTACs) resulted in compounds that induce degradation of BCL6, albeit not to complete levels. However, also these PROTACs failed to induce enhanced anti-proliferative effects in vitro [19].…”

Section: Discussionmentioning

confidence: 91%

“…However, it remains not fully investigated whether BCL6 is relevant for tumor maintenance. A variety of BCL6 inhibitors have been previously reported, several of which have demonstrated that the BTB domain of BCL6 is amenable to targeting with peptide and small molecule inhibitors (reviewed in [18]) as well as PROTACs [19]. The BTB domain is required for interaction with co-repressor complex proteins to mediate transcriptional repression [20,21].…”

Section: Introductionmentioning

confidence: 99%

“…However, their use is limited due to the low binding affinity of most of these molecules [22][23][24]. Despite recent advances in developing BCL6 inhibitors [19,[25][26][27][28], no compound has yet reached the clinic. Furthermore, there exist controversies around the rationale and the impact of targeting BCL6 as a monotherapy due to the presence of high intra-and inter-tumor heterogeneity regarding type and number of oncogenic mutations [2,3] and the possibility of oncogene addiction switching following BCL6 targeted therapies by reactivating BCL2-family dependent anti-apoptotic pathways [29].…”

Section: Introductionmentioning

confidence: 99%

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Inducible knock-out of BCL6 in lymphoma cells results in tumor stasis

et al. 2020

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Diffuse large B-cell lymphoma (DLBCL) is the most common type of non-Hodgkin lymphomas worldwide and is characterized by a high diversity of genetic and molecular alterations. Chromosomal translocations and mutations leading to deregulated expression of the transcriptional repressor BCL6 occur in a significant fraction of DLBCL patients. An oncogenic role of BCL6 in the initiation of DLBCL has been shown as the constitutive expression of BCL6 in mice recapitulates the pathogenesis of human DLBCL. However, the role of BCL6 in tumor maintenance remains poorly investigated due to the absence of suitable genetic models and limitations of pharmacological inhibitors. Here, we have utilized tetracycline-inducible CRISPR/Cas9 mutagenesis to study the consequences of BCL6 deletion in established DLBCL models in culture and in vivo. We show that BCL6 knockout in SU-DHL-4 cells in vitro results in an anti-proliferative response 4-7 days after Cas9 induction that was characterized by cell cycle (G1) arrest. Conditional BCL6 deletion in established DLBCL tumors in vivo induced a significant tumor growth inhibition with initial tumor stasis followed by slow tumor growth kinetics. Our findings support a role of BCL6 in the maintenance of lymphoma growth and showcase the utility of inducible CRISPR/ Cas9 systems for probing oncogene addiction. Recent comprehensive sequencing studies in a large cohort of DLBCL patients highlight the heterogeneity of alterations including somatic mutations, copy number alterations, and structural variants [2-4]. Among the most frequently rearranged genes are IGH, BCL2, BCL6, and MYC, with 40%, 21%, 19%, and 8% of cases affected, respectively [5-8]. BCL6 is a DNA-binding protein that represses gene transcription in Germinal Center (GC) B-cells through the recruitment of corepressor proteins. In GCs, BCL6 inhibits DNA damage response pathways and thereby prevents cell cycle arrest and apoptosis during class switch recombination and somatic hypermutation required for antibody maturation in B-cells. Subsequent BCL6 downregulation is crucial

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Section: Discussionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Inducible knock-out of BCL6 in lymphoma cells results in tumor stasis

et al. 2020

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“…Namely, the gene IRF2 was identified in MM.1S cells, Pou class 2 homeobox-associating factor 1 and Bcl6 transcriptional repressor were identified in ly1 cells, C-C motif chemokine ligand 2 and IL8 were identified in HUVEC-C cells, TCF7 was identified in KOPT-K1 cells, HMGA2 was identified in U-87 cells, and INSM transcriptional repressor 1 was identified in H2171 cells. These detected TFs have previously been reported to serve important roles in the corresponding cell lines (44)(45)(46)(47)(48). notably, it was also observed that a small number of genes were super-loaded with Brd4 in multiple cell lines, particularly MYc and Bcl2-related protein a1 (Bcl2a1).…”

Section: Brd4 Super-enriched Regions or Genes In Each Cell Line Comprmentioning

confidence: 63%

General mechanism of JQ1 in inhibiting various types of cancer

et al. 2020

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Bromodomain-containing 4 (Brd4) is a histone modification reader and transcriptional regulator that has been reported to interact with acetylated lysine histone motifs transcription factors (TFs), transcription co-activators and rna polymerase ii. The selective small molecule inhibitor JQ1, which binds competitively to bromodomains, has been reported to exhibit anti-proliferative effects in various types of cancer. Previous studies on the mechanism of action of JQ1 mostly focused on a specific tumor type or disease; however, the general mechanism through which JQ1 affects various tumors remains to be determined. in the present study, chromatin immunoprecipitation sequencing data for BRD4 and its expression profiles in six cancer cell lines were integrated and analyzed systematically. The results indicated that Brd4 binds to enhancers with histone H3 acetylated at lysine 27 (H3K27ac) and mediator complex subunit 1 in a cell type-specific manner, as well as binds to promoter regions with the oncogenic TFs MYc and e2F1 in a cell type-common manner. The cell type-common sites across the six cell types investigated were found to be functionally important for tumorigenesis, whereas the cell type-specific sites were functionally enriched with the cell identity, all of which were sensitive to JQ1 treatment. Furthermore, a core set of JQ1-regulated Brd4 binding genes were obtained, which were significantly inhibited by JQ1 in various cancer cell lines and contributed to hallmarks of cancer. These results implied a common mechanism underlying the therapeutic effects of JQ1 and suggested its potential suitability as an anti-cancer drug targeting Brd4-mediated transcriptional regulation.

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“…18,19 Targets that have been shown to be degraded by PROTACs include members of bromodomain-containing proteins such as the BET proteins (Brd2, Brd3 and Brd4), [7][8][9]14,15,17,20,21 amongst other epigenetic protein classes; [22][23][24][25][26] protein kinases; 10,12,[27][28][29][30][31] as well as non-bromodomain and non-kinase target proteins. [32][33][34][35] Recent progress in understanding principles of PROTAC mode of action, and demonstration of applicability across different target classes, suggest that PROTACs have the potential to target new protein families, including proteins that are difficult to block using current approaches.…”

Section: Introductionmentioning

confidence: 99%

Cereblon vs VHL: Hijacking E3 Ligases Against Each Other Using PROTACs

Girardini¹,

Maniaci²,

Hughes³

et al. 2019

Preprint

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<div> <div> <div> <p>The von Hippel-Lindau (VHL) and cereblon (CRBN) proteins are substrate recognition subunits of two ubiquitously expressed and biologically important Cullin RING E3 ubiquitin ligase complexes. VHL and CRBN are also the two most popular E3 ligases being recruited by bifunctional Proteolysis-targeting chimeras (PROTACs) to induce ubiquitination and subsequent proteasomal degradation of a target protein. Using homo-PROTACs, VHL and CRBN have been independently dimerized to induce their own degradation. Here we report the design, synthesis and cellular activity of VHL-CRBN hetero-dimerizing PROTACs featuring diverse conjugation patterns. We found that the most active compound 14a induced potent, rapid and profound preferential degradation of CRBN over VHL in cancer cell lines. At lower concentrations, weaker degradation of VHL was instead observed. This work demonstrates proof of concept of designing PROTACs to hijack different E3 ligases against each other, and highlights a powerful and generalizable proximity-induced strategy to achieve E3 ligase knockdown. </p> </div> </div> </div>

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Development of a Novel B-Cell Lymphoma 6 (BCL6) PROTAC To Provide Insight into Small Molecule Targeting of BCL6

Cited by 115 publications

References 40 publications

Inducible knock-out of BCL6 in lymphoma cells results in tumor stasis

Inducible knock-out of BCL6 in lymphoma cells results in tumor stasis

General mechanism of JQ1 in inhibiting various types of cancer

Cereblon vs VHL: Hijacking E3 Ligases Against Each Other Using PROTACs

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