BET INHIBITORS SUPPRESS PD-L1 TRANSCRIPTION TO ENHANCE ANTI-TUMOUR IMMUNITY AND IMMUNOTHERAPEUTIC APPROACHES
(Abstract release date: 05/19/16)
EHA Library. Hogg S. 06/11/16; 135246; S490
Mr. Simon Hogg
Contributions
Contributions
Abstract
Abstract: S490
Type: Oral Presentation
Presentation during EHA21: On Saturday, June 11, 2016 from 17:00 - 17:15
Location: Auditorium 1
Background
Bromodomain and Extra-Terminal (BET) proteins are a highly conserved family of epigenetic ‘readers’ that recognise and bind acetylated lysine residues on histones and other proteins to modulate gene expression. BET proteins are enriched at enhancer regions regulating oncogenic transcription and inhibitors (BETi) displace BET proteins from chromatin leading to suppression of oncogenes (e.g. cMYC). BETi elicit a heterogeneous range of tumour cell responses including apoptosis, growth arrest, differentiation, and senescence. However, responses to single agent BETi are self-limited in vivo and drug resistance uniformly emerges in preclinical modelling. As BET-inhibitors (BETi) are now being clinically evaluated in both haematological and solid malignancies, the focus is now shifting to the design of effective combination strategies for phase II studies.
Aims
BETi have potent anti-inflammatory properties, including chromatin-independent downregulation of NFkB signalling. However, broader mechanisms of immunomodulation by BETi in the context of anti-tumour responses remain poorly defined. Having previously discovered NK- and T-cell immunostimulatory activity of an acetyllysine mimetic fragment (n-methylpyrrolidone), we sought to evaluate the immunomodulatory activity of the prototypical theinodiazapine BETi, JQ1.
Methods
Utilising the syngeneic model of transplanted Eμ-Myc aggressive ‘Burkitt-like’ lymphoma we first compared the efficacy of JQ1 in wild-type (immunocompetent) and immunodeficient RAG1-/- or RAG2-/-cγ-/- mice. To interrogate the functional interaction between JQ1 and the immune system, we profiled changes in tumour cell immunogenicity following drug exposure by flow cytometry.
Results
We observed a 50% reduction in the survival advantage conveyed by JQ1 in mice deficient in T- and/or B-lymphocytes compared to immunocompetent controls. Notably, tumour-infiltrating lymphocytes (TILs) and peripheral blood T-cells from wild-type mice failing JQ1 therapy expressed high levels of PD-1, suggesting suppression of an endogenous anti-lymphoma immune response during disease progression. Having previously identified recurrent copy number amplification of PD-L1 (universally juxtaposed to the Eμ-Myc transgene), we hypothesised this endogenous host response may be dampened by the PD-L1/PD1 axis and further modulated by JQ1. Strikingly, JQ1 rapidly and potently suppressed PDL1 transcription in Eμ-Myc lymphoma cells in vitro and in vivo. ChIP assays revealed significantly reduced BRD4 occupancy of the PDL1 promoter/enhancer within 2 hours of JQ1 exposure (with 90% suppression of PD-L1 mRNA levels). shRNA knockdown of BRD4 likewise downregulated PD-L1 transcription. Moreover, JQ1 treatment suppressed both constitutive and IFNγ-inducible PD-L1 expression in human myeloma, Burkitt and Hodgkin cell lines. Finally, treatment of mice bearing Eμ-Myc lymphoma with JQ1 in combination with a checkpoint inhibitor (anti-PD1) or immune stimulating antibody (anti-4-1BB) was highly synergistic responses despite minimal single-agent activity of these therapeutic antibodies.
Conclusion
We suggest that oncogenic PD-L1 transcription (including IFNγ-induced expression) is directly regulated by BRD4 and can be suppressed for therapeutic gain by BETi leading to augmented anti-tumour immunity, particularly in the context of immune checkpoint inhibitors. BETi / anti-PD1 combination studies should be evaluated in genetically leveraged (e.g. cMYC positive) aggressive lymphoid malignancy.
Session topic: Non-Hodgkin & Hodgkin lymphoma - Biology
Keyword(s): B cell lymphoma, Epigenetic, Immune therapy
Type: Oral Presentation
Presentation during EHA21: On Saturday, June 11, 2016 from 17:00 - 17:15
Location: Auditorium 1
Background
Bromodomain and Extra-Terminal (BET) proteins are a highly conserved family of epigenetic ‘readers’ that recognise and bind acetylated lysine residues on histones and other proteins to modulate gene expression. BET proteins are enriched at enhancer regions regulating oncogenic transcription and inhibitors (BETi) displace BET proteins from chromatin leading to suppression of oncogenes (e.g. cMYC). BETi elicit a heterogeneous range of tumour cell responses including apoptosis, growth arrest, differentiation, and senescence. However, responses to single agent BETi are self-limited in vivo and drug resistance uniformly emerges in preclinical modelling. As BET-inhibitors (BETi) are now being clinically evaluated in both haematological and solid malignancies, the focus is now shifting to the design of effective combination strategies for phase II studies.
Aims
BETi have potent anti-inflammatory properties, including chromatin-independent downregulation of NFkB signalling. However, broader mechanisms of immunomodulation by BETi in the context of anti-tumour responses remain poorly defined. Having previously discovered NK- and T-cell immunostimulatory activity of an acetyllysine mimetic fragment (n-methylpyrrolidone), we sought to evaluate the immunomodulatory activity of the prototypical theinodiazapine BETi, JQ1.
Methods
Utilising the syngeneic model of transplanted Eμ-Myc aggressive ‘Burkitt-like’ lymphoma we first compared the efficacy of JQ1 in wild-type (immunocompetent) and immunodeficient RAG1-/- or RAG2-/-cγ-/- mice. To interrogate the functional interaction between JQ1 and the immune system, we profiled changes in tumour cell immunogenicity following drug exposure by flow cytometry.
Results
We observed a 50% reduction in the survival advantage conveyed by JQ1 in mice deficient in T- and/or B-lymphocytes compared to immunocompetent controls. Notably, tumour-infiltrating lymphocytes (TILs) and peripheral blood T-cells from wild-type mice failing JQ1 therapy expressed high levels of PD-1, suggesting suppression of an endogenous anti-lymphoma immune response during disease progression. Having previously identified recurrent copy number amplification of PD-L1 (universally juxtaposed to the Eμ-Myc transgene), we hypothesised this endogenous host response may be dampened by the PD-L1/PD1 axis and further modulated by JQ1. Strikingly, JQ1 rapidly and potently suppressed PDL1 transcription in Eμ-Myc lymphoma cells in vitro and in vivo. ChIP assays revealed significantly reduced BRD4 occupancy of the PDL1 promoter/enhancer within 2 hours of JQ1 exposure (with 90% suppression of PD-L1 mRNA levels). shRNA knockdown of BRD4 likewise downregulated PD-L1 transcription. Moreover, JQ1 treatment suppressed both constitutive and IFNγ-inducible PD-L1 expression in human myeloma, Burkitt and Hodgkin cell lines. Finally, treatment of mice bearing Eμ-Myc lymphoma with JQ1 in combination with a checkpoint inhibitor (anti-PD1) or immune stimulating antibody (anti-4-1BB) was highly synergistic responses despite minimal single-agent activity of these therapeutic antibodies.
Conclusion
We suggest that oncogenic PD-L1 transcription (including IFNγ-induced expression) is directly regulated by BRD4 and can be suppressed for therapeutic gain by BETi leading to augmented anti-tumour immunity, particularly in the context of immune checkpoint inhibitors. BETi / anti-PD1 combination studies should be evaluated in genetically leveraged (e.g. cMYC positive) aggressive lymphoid malignancy.
Session topic: Non-Hodgkin & Hodgkin lymphoma - Biology
Keyword(s): B cell lymphoma, Epigenetic, Immune therapy
Abstract: S490
Type: Oral Presentation
Presentation during EHA21: On Saturday, June 11, 2016 from 17:00 - 17:15
Location: Auditorium 1
Background
Bromodomain and Extra-Terminal (BET) proteins are a highly conserved family of epigenetic ‘readers’ that recognise and bind acetylated lysine residues on histones and other proteins to modulate gene expression. BET proteins are enriched at enhancer regions regulating oncogenic transcription and inhibitors (BETi) displace BET proteins from chromatin leading to suppression of oncogenes (e.g. cMYC). BETi elicit a heterogeneous range of tumour cell responses including apoptosis, growth arrest, differentiation, and senescence. However, responses to single agent BETi are self-limited in vivo and drug resistance uniformly emerges in preclinical modelling. As BET-inhibitors (BETi) are now being clinically evaluated in both haematological and solid malignancies, the focus is now shifting to the design of effective combination strategies for phase II studies.
Aims
BETi have potent anti-inflammatory properties, including chromatin-independent downregulation of NFkB signalling. However, broader mechanisms of immunomodulation by BETi in the context of anti-tumour responses remain poorly defined. Having previously discovered NK- and T-cell immunostimulatory activity of an acetyllysine mimetic fragment (n-methylpyrrolidone), we sought to evaluate the immunomodulatory activity of the prototypical theinodiazapine BETi, JQ1.
Methods
Utilising the syngeneic model of transplanted Eμ-Myc aggressive ‘Burkitt-like’ lymphoma we first compared the efficacy of JQ1 in wild-type (immunocompetent) and immunodeficient RAG1-/- or RAG2-/-cγ-/- mice. To interrogate the functional interaction between JQ1 and the immune system, we profiled changes in tumour cell immunogenicity following drug exposure by flow cytometry.
Results
We observed a 50% reduction in the survival advantage conveyed by JQ1 in mice deficient in T- and/or B-lymphocytes compared to immunocompetent controls. Notably, tumour-infiltrating lymphocytes (TILs) and peripheral blood T-cells from wild-type mice failing JQ1 therapy expressed high levels of PD-1, suggesting suppression of an endogenous anti-lymphoma immune response during disease progression. Having previously identified recurrent copy number amplification of PD-L1 (universally juxtaposed to the Eμ-Myc transgene), we hypothesised this endogenous host response may be dampened by the PD-L1/PD1 axis and further modulated by JQ1. Strikingly, JQ1 rapidly and potently suppressed PDL1 transcription in Eμ-Myc lymphoma cells in vitro and in vivo. ChIP assays revealed significantly reduced BRD4 occupancy of the PDL1 promoter/enhancer within 2 hours of JQ1 exposure (with 90% suppression of PD-L1 mRNA levels). shRNA knockdown of BRD4 likewise downregulated PD-L1 transcription. Moreover, JQ1 treatment suppressed both constitutive and IFNγ-inducible PD-L1 expression in human myeloma, Burkitt and Hodgkin cell lines. Finally, treatment of mice bearing Eμ-Myc lymphoma with JQ1 in combination with a checkpoint inhibitor (anti-PD1) or immune stimulating antibody (anti-4-1BB) was highly synergistic responses despite minimal single-agent activity of these therapeutic antibodies.
Conclusion
We suggest that oncogenic PD-L1 transcription (including IFNγ-induced expression) is directly regulated by BRD4 and can be suppressed for therapeutic gain by BETi leading to augmented anti-tumour immunity, particularly in the context of immune checkpoint inhibitors. BETi / anti-PD1 combination studies should be evaluated in genetically leveraged (e.g. cMYC positive) aggressive lymphoid malignancy.
Session topic: Non-Hodgkin & Hodgkin lymphoma - Biology
Keyword(s): B cell lymphoma, Epigenetic, Immune therapy
Type: Oral Presentation
Presentation during EHA21: On Saturday, June 11, 2016 from 17:00 - 17:15
Location: Auditorium 1
Background
Bromodomain and Extra-Terminal (BET) proteins are a highly conserved family of epigenetic ‘readers’ that recognise and bind acetylated lysine residues on histones and other proteins to modulate gene expression. BET proteins are enriched at enhancer regions regulating oncogenic transcription and inhibitors (BETi) displace BET proteins from chromatin leading to suppression of oncogenes (e.g. cMYC). BETi elicit a heterogeneous range of tumour cell responses including apoptosis, growth arrest, differentiation, and senescence. However, responses to single agent BETi are self-limited in vivo and drug resistance uniformly emerges in preclinical modelling. As BET-inhibitors (BETi) are now being clinically evaluated in both haematological and solid malignancies, the focus is now shifting to the design of effective combination strategies for phase II studies.
Aims
BETi have potent anti-inflammatory properties, including chromatin-independent downregulation of NFkB signalling. However, broader mechanisms of immunomodulation by BETi in the context of anti-tumour responses remain poorly defined. Having previously discovered NK- and T-cell immunostimulatory activity of an acetyllysine mimetic fragment (n-methylpyrrolidone), we sought to evaluate the immunomodulatory activity of the prototypical theinodiazapine BETi, JQ1.
Methods
Utilising the syngeneic model of transplanted Eμ-Myc aggressive ‘Burkitt-like’ lymphoma we first compared the efficacy of JQ1 in wild-type (immunocompetent) and immunodeficient RAG1-/- or RAG2-/-cγ-/- mice. To interrogate the functional interaction between JQ1 and the immune system, we profiled changes in tumour cell immunogenicity following drug exposure by flow cytometry.
Results
We observed a 50% reduction in the survival advantage conveyed by JQ1 in mice deficient in T- and/or B-lymphocytes compared to immunocompetent controls. Notably, tumour-infiltrating lymphocytes (TILs) and peripheral blood T-cells from wild-type mice failing JQ1 therapy expressed high levels of PD-1, suggesting suppression of an endogenous anti-lymphoma immune response during disease progression. Having previously identified recurrent copy number amplification of PD-L1 (universally juxtaposed to the Eμ-Myc transgene), we hypothesised this endogenous host response may be dampened by the PD-L1/PD1 axis and further modulated by JQ1. Strikingly, JQ1 rapidly and potently suppressed PDL1 transcription in Eμ-Myc lymphoma cells in vitro and in vivo. ChIP assays revealed significantly reduced BRD4 occupancy of the PDL1 promoter/enhancer within 2 hours of JQ1 exposure (with 90% suppression of PD-L1 mRNA levels). shRNA knockdown of BRD4 likewise downregulated PD-L1 transcription. Moreover, JQ1 treatment suppressed both constitutive and IFNγ-inducible PD-L1 expression in human myeloma, Burkitt and Hodgkin cell lines. Finally, treatment of mice bearing Eμ-Myc lymphoma with JQ1 in combination with a checkpoint inhibitor (anti-PD1) or immune stimulating antibody (anti-4-1BB) was highly synergistic responses despite minimal single-agent activity of these therapeutic antibodies.
Conclusion
We suggest that oncogenic PD-L1 transcription (including IFNγ-induced expression) is directly regulated by BRD4 and can be suppressed for therapeutic gain by BETi leading to augmented anti-tumour immunity, particularly in the context of immune checkpoint inhibitors. BETi / anti-PD1 combination studies should be evaluated in genetically leveraged (e.g. cMYC positive) aggressive lymphoid malignancy.
Session topic: Non-Hodgkin & Hodgkin lymphoma - Biology
Keyword(s): B cell lymphoma, Epigenetic, Immune therapy
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