Project description:Recent evidence suggests that inhibition of BET epigenetic readers may have clinical utility in hematological malignancies. We demonstrate the efficacy of the BET inhibitor I-BET151 across a variety of AML subtypes, and demonstrate that a common core transcriptional program, which is HOX gene-independent, is downregulated in AML subtypes sensitive to I-BET treatment. Focusing on the most common mutation in AML, we present evidence to suggest that wildtype NPM1 has an inhibitory influence on BRD4, which is relieved upon NPM1c mutation and cytosplasmic dislocation. NPM1c mutation allows upregulation of the core transcriptional program facilitating leukemia development, and this program is abrogated by I-BET therapy. Finally, we demonstrate the efficacy of I-BET151 in human cell lines, a unique murine model and in primary patient samples of NPM1c AML. This submission only includes samples from the human cell line.
Project description:Recent evidence suggests that inhibition of bromodomain and extra-terminal (BET) epigenetic readers may have clinical utility against acute myeloid leukemia (AML). Here we validate this hypothesis, demonstrating the efficacy of the BET inhibitor I-BET151 across a variety of AML subtypes driven by disparate mutations. We demonstrate that a common 'core' transcriptional program, which is HOX gene independent, is downregulated in AML and underlies sensitivity to I-BET treatment. This program is enriched for genes that contain 'super-enhancers', recently described regulatory elements postulated to control key oncogenic driver genes. Moreover, our program can independently classify AML patients into distinct cytogenetic and molecular subgroups, suggesting that it contains biomarkers of sensitivity and response. We focus AML with mutations of the Nucleophosmin gene (NPM1) and show evidence to suggest that wild-type NPM1 has an inhibitory influence on BRD4 that is relieved upon NPM1c mutation and cytosplasmic dislocation. This leads to the upregulation of the core transcriptional program facilitating leukemia development. This program is abrogated by I-BET therapy and by nuclear restoration of NPM1. Finally, we demonstrate the efficacy of I-BET151 in a unique murine model and in primary patient samples of NPM1c AML. Taken together, our data support the use of BET inhibitors in clinical trials in AML.
Project description:The BET (bromodomain and extra terminal) protein family members including BRD4 bind to acetylated lysines on histones and regulate the expression of important oncogenes, e.g., MYC and BCL2. Here we demonstrate the sensitizing effects of the histone hyperacetylation inducing pan-histone deacetylase inhibitor (HDI) panobinostat (PS) on human AML blast progenitor cells (BPCs) to the BET protein inhibitor JQ1. Treatment with JQ1 but not its inactive enantiomer (R-JQ1) was highly lethal against AML BPCs expressing mutant NPM1c+ with or without co-expression of FLT3-ITD, or AML expressing MLL fusion oncoprotein. JQ1 treatment reduced binding of BRD4 and RNA polymerase II to the DNA of MYC and BCL2, and reduced their levels in the AML cells. Co-treatment with JQ1 and the HDAC inhibitor panobinostat (PS) synergistically induced apoptosis of the AML BPCs, but not of normal CD34+ hematopoietic progenitor cells. This was associated with greater attenuation of MYC and BCL2, while increasing p21, BIM and cleaved PARP levels in the AML BPCs. Co-treatment with JQ1 and PS significantly improved the survival of the NOD/SCID mice engrafted with OCI-AML3 or MOLM13 cells (p < 0.01). These findings highlight co-treatment with a BRD4 antagonist and an HDI as a potentially efficacious therapy of AML. Two samples were analyzed (untreated cells, cells treated with JQ1)
Project description:Nucleophosmin (NPM1) is a ubiquitously expressed nucleolar protein with a wide range of functions including ribosome biogenesis, mRNA processing, and maintenance of genomic stability1-4. In acute myeloid leukemia (AML), the terminal exon of NPM1 is often mutated (~30% of adult AMLs), resulting in the change of the nucleolar localization signal into a nuclear export signal and a shift of the protein to the cytoplasm (NPM1c)2,3,5. AMLs carrying this mutation have aberrant expression of the HOXA genes, whose overexpression leads to leukemogenic transformation6-8. Recently, it was shown that depletion or re-localization of the NPM1c protein into the nucleus causes downregulation of the HOXA genes, leading to the speculation that NPM1c directly regulates their transcription9-11. Here, we show that NPM1c binds to a subset of active gene promoters marked with high levels of H3K27ac in NPM1c leukemia cell lines and primary leukemia blasts, including well-known leukemia-driving genes such as posterior HOXA, HOXB, and MEIS1/PBX3 genes as well as novel targets IRX5 and NKX2-3. The binding of NPM1c on chromatin sustains active transcription of key target genes by maintaining high local-concentration of transcriptional complexes, including the Super Elongation Complex (SEC) and Menin/MLL1. NPM1c also maintains the active chromatin landscape by inhibiting the activity of histone deacetylases (HDACs). Depletion of NPM1c causes histone deacetylation and the silencing of key leukemic genes, leading to cell differentiation and growth arrest. The export protein XPO1 plays a key role by tethering NPM1c onto chromatin. The combination of XPO1 inhibitors (e.g., Selinexor and Eltanexor) with the Menin inhibitor MI-3454 has a synergistic effect on inducing differentiation in both NPM1-mutated leukemia cell lines and PDX model. Together, these findings reveal the neomorphic function of NPM1c as transactivator for leukemic gene expression and open up potential avenues for therapeutic intervention.
Project description:Nucleophosmin (NPM1) is a ubiquitously expressed nucleolar protein with a wide range of functions including ribosome biogenesis, mRNA processing, and maintenance of genomic stability1-4. In acute myeloid leukemia (AML), the terminal exon of NPM1 is often mutated (~30% of adult AMLs), resulting in the change of the nucleolar localization signal into a nuclear export signal and a shift of the protein to the cytoplasm (NPM1c)2,3,5. AMLs carrying this mutation have aberrant expression of the HOXA genes, whose overexpression leads to leukemogenic transformation6-8. Recently, it was shown that depletion or re-localization of the NPM1c protein into the nucleus causes downregulation of the HOXA genes, leading to the speculation that NPM1c directly regulates their transcription9-11. Here, we show that NPM1c binds to a subset of active gene promoters marked with high levels of H3K27ac in NPM1c leukemia cell lines and primary leukemia blasts, including well-known leukemia-driving genes such as posterior HOXA, HOXB, and MEIS1/PBX3 genes as well as novel targets IRX5 and NKX2-3. The binding of NPM1c on chromatin sustains active transcription of key target genes by maintaining high local-concentration of transcriptional complexes, including the Super Elongation Complex (SEC) and Menin/MLL1. NPM1c also maintains the active chromatin landscape by inhibiting the activity of histone deacetylases (HDACs). Depletion of NPM1c causes histone deacetylation and the silencing of key leukemic genes, leading to cell differentiation and growth arrest. The export protein XPO1 plays a key role by tethering NPM1c onto chromatin. The combination of XPO1 inhibitors (e.g., Selinexor and Eltanexor) with the Menin inhibitor MI-3454 has a synergistic effect on inducing differentiation in both NPM1-mutated leukemia cell lines and PDX model. Together, these findings reveal the neomorphic function of NPM1c as transactivator for leukemic gene expression and open up potential avenues for therapeutic intervention.
Project description:Nucleophosmin (NPM1) is a ubiquitously expressed nucleolar protein with a wide range of functions including ribosome biogenesis, mRNA processing, and maintenance of genomic stability1-4. In acute myeloid leukemia (AML), the terminal exon of NPM1 is often mutated (~30% of adult AMLs), resulting in the change of the nucleolar localization signal into a nuclear export signal and a shift of the protein to the cytoplasm (NPM1c)2,3,5. AMLs carrying this mutation have aberrant expression of the HOXA genes, whose overexpression leads to leukemogenic transformation6-8. Recently, it was shown that depletion or re-localization of the NPM1c protein into the nucleus causes downregulation of the HOXA genes, leading to the speculation that NPM1c directly regulates their transcription9-11. Here, we show that NPM1c binds to a subset of active gene promoters marked with high levels of H3K27ac in NPM1c leukemia cell lines and primary leukemia blasts, including well-known leukemia-driving genes such as posterior HOXA, HOXB, and MEIS1/PBX3 genes as well as novel targets IRX5 and NKX2-3. The binding of NPM1c on chromatin sustains active transcription of key target genes by maintaining high local-concentration of transcriptional complexes, including the Super Elongation Complex (SEC) and Menin/MLL1. NPM1c also maintains the active chromatin landscape by inhibiting the activity of histone deacetylases (HDACs). Depletion of NPM1c causes histone deacetylation and the silencing of key leukemic genes, leading to cell differentiation and growth arrest. The export protein XPO1 plays a key role by tethering NPM1c onto chromatin. The combination of XPO1 inhibitors (e.g., Selinexor and Eltanexor) with the Menin inhibitor MI-3454 has a synergistic effect on inducing differentiation in both NPM1-mutated leukemia cell lines and PDX model. Together, these findings reveal the neomorphic function of NPM1c as transactivator for leukemic gene expression and open up potential avenues for therapeutic intervention.
Project description:Nucleophosmin (NPM1) is a ubiquitously expressed nucleolar protein with a wide range of functions including ribosome biogenesis, mRNA processing, and maintenance of genomic stability1-4. In acute myeloid leukemia (AML), the terminal exon of NPM1 is often mutated (~30% of adult AMLs), resulting in the change of the nucleolar localization signal into a nuclear export signal and a shift of the protein to the cytoplasm (NPM1c)2,3,5. AMLs carrying this mutation have aberrant expression of the HOXA genes, whose overexpression leads to leukemogenic transformation6-8. Recently, it was shown that depletion or re-localization of the NPM1c protein into the nucleus causes downregulation of the HOXA genes, leading to the speculation that NPM1c directly regulates their transcription9-11. Here, we show that NPM1c binds to a subset of active gene promoters marked with high levels of H3K27ac in NPM1c leukemia cell lines and primary leukemia blasts, including well-known leukemia-driving genes such as posterior HOXA, HOXB, and MEIS1/PBX3 genes as well as novel targets IRX5 and NKX2-3. The binding of NPM1c on chromatin sustains active transcription of key target genes by maintaining high local-concentration of transcriptional complexes, including the Super Elongation Complex (SEC) and Menin/MLL1. NPM1c also maintains the active chromatin landscape by inhibiting the activity of histone deacetylases (HDACs). Depletion of NPM1c causes histone deacetylation and the silencing of key leukemic genes, leading to cell differentiation and growth arrest. The export protein XPO1 plays a key role by tethering NPM1c onto chromatin. The combination of XPO1 inhibitors (e.g., Selinexor and Eltanexor) with the Menin inhibitor MI-3454 has a synergistic effect on inducing differentiation in both NPM1-mutated leukemia cell lines and PDX model. Together, these findings reveal the neomorphic function of NPM1c as transactivator for leukemic gene expression and open up potential avenues for therapeutic intervention.
Project description:Nucleophosmin (NPM1) is a ubiquitously expressed nucleolar protein with a wide range of functions including ribosome biogenesis, mRNA processing, and maintenance of genomic stability1-4. In acute myeloid leukemia (AML), the terminal exon of NPM1 is often mutated (~30% of adult AMLs), resulting in the change of the nucleolar localization signal into a nuclear export signal and a shift of the protein to the cytoplasm (NPM1c)2,3,5. AMLs carrying this mutation have aberrant expression of the HOXA genes, whose overexpression leads to leukemogenic transformation6-8. Recently, it was shown that depletion or re-localization of the NPM1c protein into the nucleus causes downregulation of the HOXA genes, leading to the speculation that NPM1c directly regulates their transcription9-11. Here, we show that NPM1c binds to a subset of active gene promoters marked with high levels of H3K27ac in NPM1c leukemia cell lines and primary leukemia blasts, including well-known leukemia-driving genes such as posterior HOXA, HOXB, and MEIS1/PBX3 genes as well as novel targets IRX5 and NKX2-3. The binding of NPM1c on chromatin sustains active transcription of key target genes by maintaining high local-concentration of transcriptional complexes, including the Super Elongation Complex (SEC) and Menin/MLL1. NPM1c also maintains the active chromatin landscape by inhibiting the activity of histone deacetylases (HDACs). Depletion of NPM1c causes histone deacetylation and the silencing of key leukemic genes, leading to cell differentiation and growth arrest. The export protein XPO1 plays a key role by tethering NPM1c onto chromatin. The combination of XPO1 inhibitors (e.g., Selinexor and Eltanexor) with the Menin inhibitor MI-3454 has a synergistic effect on inducing differentiation in both NPM1-mutated leukemia cell lines and PDX model. Together, these findings reveal the neomorphic function of NPM1c as transactivator for leukemic gene expression and open up potential avenues for therapeutic intervention.
Project description:Acute myeloid leukemia (AML) pathogenesis often involves a mutation in the NPM1 nucleolar chaperone, but the bases for its transforming properties and association with favorable outcome remain incompletely understood. Here we demonstrate that an oncogenic mutant form of NPM1 (NPM1c) hampers formation of PML nuclear bodies (NBs), key senescence effectors, and impairs mitochondrial function to drive an integrated stress response. Actinomycin D (ActD), an antibiotic with unambiguous clinical efficacy in relapsed/refractory NPM1c-AMLs, preferentially targets these primed mitochondria, activating cGAS signaling and boosting ROS production. The later restores PML NB formation to drive senescence of NPM1c-AMLs cells. Dual targeting of mitochondria by Venetoclax and ActD synergized for AML elimination. Our studies reveal a central role of mitochondria downstream of NPM1c and implicate a mitochondrial/ROS/PML/TP53 senescence pathway as a key effector of ActD-based, and possibly others, chemotherapies.
Project description:Primary skin fibroblasts from a HGPS patient and an age-matched control wild-type individual were challenged in a standard transformation assay by retroviral introduction of TERT (T), V12-HRAS (R) and SV40 large and small T antigens (S). Knock-down of BRD4 in this TRS-HGPS cell line (TRS-HGPS-shBRD4) was achieved by retroviral introduction of independent shRNAs (shBRD4-1 to -3) Abstract: Advanced age and DNA damage accumulation are strong risk factors for cancer. The premature-aging disorder Hutchinson Gilford Progeria Syndrome (HGPS) provides a unique opportunity to study the interplay between DNA damage and aging-associated tumor mechanisms, since HGPS patients do not develop tumors despite elevated levels of DNA damage. Here, we have used HGPS patient cells to identify a protective mechanism to oncogenesis. We find that HGPS cells are resistant to neo-plastic transformation. This resistance is mediated by the bromodomain protein BRD4, which exhibits altered genome-wide binding patterns in transformation-resistant cells leading to inhibition of oncogenic de-differentiation. BRD4 also in-hibits, albeit to a lower extent, the tumorigenic potential of transformed cells from healthy individuals and BRD4-mediated tumor protection is clinically relevant, since a BRD4 gene signature predicts positive clinical outcome in breast and lung cancer. Our results demonstrate a protective function for BRD4 and suggest tissue-specific functions for BRD4 in tumorigenesis. 2 biological replicates are included for TRS-WT and TRS-HGPS cell lines. 3 biological replicates are included for TRS-HGPS-shBRD4 (derived from 3 independent shRNAs against BRD4)