Project description:NUT carcinoma (NC) is an aggressive cancer with no effective treatment. About 70% of NUT carcinoma is associated with chromosome translocation events that lead to the formation of a BRD4::NUTM1 fusion gene. Because the BRD4::NUTM1 gene is unequivocally cytotoxic when ectopically expressed in cell lines, questions remain on whether the fusion gene can initiate NC. Here, we report the first genetically engineered mouse model (GEMM) for NUT carcinoma that recapitulates the t(15;19) chromosome translocation in mice. We demonstrated that the mouse t(2;17) syntenic chromosome translocation, forming the Brd4::Nutm1 fusion gene, could induce aggressive carcinomas in mice. The tumors present histopathological and molecular features similar to human NC, with an enrichment of undifferentiated cells. Similar to the reports of human NC incidence, Brd4::Nutm1 can induce NC from a broad range of tissues with a strong phenotypical variability. The consistent induction of poorly differentiated carcinoma demonstrated a strong reprogramming activity of BRD4::NUTM1. The new mouse model provided a critical preclinical model for NC that will lead to better understanding and therapy development for NC.
Project description:NUT carcinoma (NC) is an aggressive cancer with no effective treatment. About 70% of NUT carcinoma is associated with chromosome translocation events that lead to the formation of a BRD4::NUTM1 fusion gene. Because the BRD4::NUTM1 gene is unequivocally cytotoxic when ectopically expressed in cell lines, questions remain on whether the fusion gene can initiate NC. Here, we report the first genetically engineered mouse model (GEMM) for NUT carcinoma that recapitulates the t(15;19) chromosome translocation in mice. We demonstrated that the mouse t(2;17) syntenic chromosome translocation, forming the Brd4::Nutm1 fusion gene, could induce aggressive carcinomas in mice. The tumors present histopathological and molecular features similar to human NC, with an enrichment of undifferentiated cells. Similar to the reports of human NC incidence, Brd4::Nutm1 can induce NC from a broad range of tissues with a strong phenotypical variability. The consistent induction of poorly differentiated carcinoma demonstrated a strong reprogramming activity of BRD4::NUTM1. The new mouse model provided a critical preclinical model for NC that will lead to better understanding and therapy development for NC.
Project description:To investigate the mechanism that drives dramatic mistargeting of active chromatin in NUT midline carcinoma, we have identified protein interactions unique to the BRD4-NUT fusion oncoprotein compared to wild type BRD4. Using crosslinking, affinity purification, and mass spectrometry, we identified the EP300 acetyltransferase as uniquely associated with BRD4 through the NUT fusion in both NMC and non-NMC cell types. We also discovered ZNF532 among a small number of candidates associated with BRD4-NUT in NMC patient cells but not present in 293T cells.
Project description:Aberrant formation of biomolecular condensates has been proposed to play a role in several cancers. The oncogenic fusion protein BRD4-NUT forms condensates and drives changes in gene expression in Nut Carcinoma (NC). Here we sought to understand the molecular elements of BRD4-NUT and its associated histone acetyltransferase (HAT), p300, that promote these activities. We determined that a minimal fragment of NUT (MIN) in fusion with BRD4 is necessary and sufficient to bind p300 and form condensates. Furthermore, a BRD4-p300 fusion protein also forms condensates and drives gene expression similarly to BRD4-NUT(MIN), suggesting the p300 fusion may mimic certain features of BRD4-NUT. The intrinsically disordered regions, transcription factor-binding domains, and HAT activity of p300 all collectively contribute to condensate formation by BRD4-p300, suggesting that these elements might contribute to condensate formation by BRD4-NUT. Conversely, only the HAT activity of BRD4-p300 appears necessary to mimic the transcriptional profile of cells expressing BRD4-NUT. Our results suggest a model for condensate formation by the BRD4-NUT:p300 complex involving a combination of positive feedback and phase separation, and show that multiple overlapping, yet distinct, regions of p300 contribute to condensate formation and transcriptional regulation.
Project description:Aberrant formation of biomolecular condensates has been proposed to play a role in several cancers. The oncogenic fusion protein BRD4-NUT forms condensates and drives changes in gene expression in Nut Carcinoma (NC). Here we sought to understand the molecular elements of BRD4-NUT and its associated histone acetyltransferase (HAT), p300, that promote these activities. We determined that a minimal fragment of NUT (MIN) in fusion with BRD4 is necessary and sufficient to bind p300 and form condensates. Furthermore, a BRD4-p300 fusion protein also forms condensates and drives gene expression similarly to BRD4-NUT(MIN), suggesting the p300 fusion may mimic certain features of BRD4-NUT. The intrinsically disordered regions, transcription factor-binding domains, and HAT activity of p300 all collectively contribute to condensate formation by BRD4-p300, suggesting that these elements might contribute to condensate formation by BRD4-NUT. Conversely, only the HAT activity of BRD4-p300 appears necessary to mimic the transcriptional profile of cells expressing BRD4-NUT. Our results suggest a model for condensate formation by the BRD4-NUT:p300 complex involving a combination of positive feedback and phase separation, and show that multiple overlapping, yet distinct, regions of p300 contribute to condensate formation and transcriptional regulation.
Project description:To investigate the mechanism that drives dramatic mistargeting of active chromatin in NUT-midline carcinoma, we have identified protein interactions unique to the BRD4-NUT fusion oncoprotein compared to wild type BRD4. Using crosslinking, affinity purification, and mass spectrometry, we identify the p300 acetyltransferase as ectopically associated with BRD4 through the NUT fusion in both NMC and non-NMC cell types. We also identify ZNF532 among a number of candidates uniquely associated with BRD4-NUT in NMC patient cells but not present in 293T cells. p300 and ZNF532 are both implicated in feed-forward regulatory loops leading to propagation of the oncogenic regulatory complex in BRD4-NUT patient cells. Extending our biochemical findings, we independently identified a novel ZNF532-NUT translocation fusion in a newly diagnosed NMC patient. ChIP-seq of key players: NUT, ZNF532, BRD4, p300, and anti-H3K27ac, reveals the formation of ZNF532-NUT-associated hyperacetylated megadomains, distinctly localized, but otherwise analogous to those found in BRD4-NUT patient cells. Our results support a model in which NMC is caused by a cascade of misregulation that is initiated by ectopic protein-protein interactions on chromatin between NUT and several distinct, but interacting, components of BRD4 regulatory complexes.
Project description:Discarded live tumor tissue from a metastatic focus in the patientM-bM-^@M-^Ys lung was collected under institutional review board approval through the NUT midline carcinoma registry (www.NMCRegistry.org). From this tissue the first known NUT-variant cell line, 1221, was established. To determine the putative partner gene to NUT, we performed comprehensive RNA-sequencing on RNA purified from 1221. We identified an in-frame transcript fusing the 5M-bM-^@M-^Y coding sequence of NSD3 (exons 1-7) to exons 2-7 of NUT. Expression of the NSD3-NUT fusion oncoprotein was verified by immunobloting with an antibody to NUT, revealing an approximately 200kDa band that is similar in size to BRD3-NUT, but smaller than BRD4-NUT Identification of a NUT fusion partner using RNA extracted from live cultured 1221 cell line derived from a lung metastasis from the index case of a 13 year old female with NUT-positive NMC.
Project description:NUT carcinoma (NC), an aggressive carcinoma, is driven by the BRD4-NUT fusion oncoprotein. BRD4, a BET protein, binds to chromatin through its two bromodomains, and when fused to NUT forms very large super-enhancers, termed megadomains. Targeting BRD4-NUT with BET bromodomain inhibitors (BETi) are a promising treatment, but limited as monotherapy. To identify additional dependencies in NC, we performed a genetic rescue screen in NC cells depleted of BRD4-NUT and identified EZH2 as a top correlated hit. Indeed, inhibition of EZH2 using the clinical compound, tazemetostat (taz), potently blocked growth of NC cells, and when combined with BETi was highly synergistic. Epigenetic and transcriptomic analysis revealed that taz reversed the EZH2-specific H3K27me3 silencing mark, and restored expression of multiple tumor suppressor genes while having no effect on megadomain-associated genes. CDKN2A was identified as the only amongst all taz-derepressed genes to confer resistance to taz in a CRISPR-CAS9 screen. In pre-clinical models, combined taz and BETi synergistically blocked growth and prolonged survival of NC-xenografted mice, with all mice cured in one cohort.
Project description:Knockdown of the oncogene, BRD4-NUT, in a rare cancer, termed NUTmidline carcinoma (NMC), results in morphologic features consistent with squamous differentiation. Treatment with the HDAC-inhibitor, TSA, appears to cause the same phenotype. Here, we use gene expression profiling to compare the changes in gene expression following BRD4-NUT knockdown and TSA treatment. RNA was extracted from two BRD4-NUT-expressing NMC cell lines, PER-403 and TC-797, 24h following siRNA knockdown versus control in duplicate. RNA was extracted from two BRD4-NUT-expressing NMC cell lines, PER-403 and TC-797, 24h following treatment with TSA versus etoh control in triplicate