AKT ACTIVATION IN CHRONIC LYMPHOCYTIC LEUKEMIA CELLS PROMOTES TRANSFORMATION TOWARDS AGGRESSIVE RICHTER'S SYNDROME LYMPHOMA
(Abstract release date: 05/19/16)
EHA Library. Pallasch C. 06/10/16; 135151; S118
Dr. Christian Pallasch
Contributions
Contributions
Abstract
Abstract: S118
Type: Oral Presentation
Presentation during EHA21: On Friday, June 10, 2016 from 12:30 - 12:45
Location: Auditorium 2
Background
Richter's syndrome (RS) is an aggressive transformation of Chronic Lymphocytic Leukemia (CLL) refractory to current therapies with dismal prognosis. RS arises from CLL cells independent of common DLBCL-mutations. Frequently mutations in p53, CDKN2 or cMyc genes are involved, but a significant proportion displays no specifically acquired driver mutation.
Aims
Here we aim to elucidate the role of AKT in transformation towards Richter´s syndrome in human patients and functionally address constitutively AKT-activation in vivo. Ultimately, we aim to develop mouse models that can be used to develop novel treatment options towards Richter´s syndrome.
Methods
FFPE sections of Richter syndrome patients were used for pAKT staining. We have developed a mouse model allowing for Cre-activatable expression of a myristoylated AKT constitutive active allele from the Rosa26 locus (AKT-C). We crossed that mice with Cd19Cre- and Cg1Cre-mediated B cell-specific AKT-C expression in the Eµ:Tcl1 CLL mouse model.
Results
In biopsies revealed from patients with RS one third of cases showed enhanced AKT activation. Strikingly, Richter's transformation was recapitulated when AKT was genetically over-activated in Eµ-Tcl-1 mice, where AKT-C expressing cells developed a high-grade lymphoma phenotype leading to significantly decreased survival. AKT-C expression in TCL1 mouse model CLL cells furthermore induced morphology changes displaying features of aggressive lymphoma such as large transformed B-cell phenotype and frequent mitotic figures, enhanced proliferation indicated by KI67. The phenotype of transformed aggressive lymphoma could be revealed independently in both Cd19Cre- and Cg1Cre-mediated activation of AKT. Thus, Eµ:Tcl1 transformed CLL cells act in concert with constitutively active AKT to develop RS.Noteworthy, Cd19Cre;AKT-C double transgenic mice fail to develop leukemia and lymphoma, indicating that CLL development in Eµ:Tcl1 mice is a precondition to transformation. As for the downstream mechanisms of AKT-mediated transformation we identified GSK-3b inhibition and subsequent cMyc and Mcl-1 stabilization. This might confer contribute to resistance of RS cells against DNA-damaging and PI3K-inhibiting compounds in this novel model of Richter´s syndrome.
Conclusion
Collectively, we have generated the first murine Richter´s Syndrome model providing novel mechanistic insights into the molecular understanding of Richter's transformation as an AKT-driven disease. The new model is amenable to model therapeutic strategies and to address the efficacy of synergistic treatment combinations in transformed lymphoma.
Session topic: CLL natural history and progression
Keyword(s): Akt, Mouse model, Signal transduction, Transformation
Type: Oral Presentation
Presentation during EHA21: On Friday, June 10, 2016 from 12:30 - 12:45
Location: Auditorium 2
Background
Richter's syndrome (RS) is an aggressive transformation of Chronic Lymphocytic Leukemia (CLL) refractory to current therapies with dismal prognosis. RS arises from CLL cells independent of common DLBCL-mutations. Frequently mutations in p53, CDKN2 or cMyc genes are involved, but a significant proportion displays no specifically acquired driver mutation.
Aims
Here we aim to elucidate the role of AKT in transformation towards Richter´s syndrome in human patients and functionally address constitutively AKT-activation in vivo. Ultimately, we aim to develop mouse models that can be used to develop novel treatment options towards Richter´s syndrome.
Methods
FFPE sections of Richter syndrome patients were used for pAKT staining. We have developed a mouse model allowing for Cre-activatable expression of a myristoylated AKT constitutive active allele from the Rosa26 locus (AKT-C). We crossed that mice with Cd19Cre- and Cg1Cre-mediated B cell-specific AKT-C expression in the Eµ:Tcl1 CLL mouse model.
Results
In biopsies revealed from patients with RS one third of cases showed enhanced AKT activation. Strikingly, Richter's transformation was recapitulated when AKT was genetically over-activated in Eµ-Tcl-1 mice, where AKT-C expressing cells developed a high-grade lymphoma phenotype leading to significantly decreased survival. AKT-C expression in TCL1 mouse model CLL cells furthermore induced morphology changes displaying features of aggressive lymphoma such as large transformed B-cell phenotype and frequent mitotic figures, enhanced proliferation indicated by KI67. The phenotype of transformed aggressive lymphoma could be revealed independently in both Cd19Cre- and Cg1Cre-mediated activation of AKT. Thus, Eµ:Tcl1 transformed CLL cells act in concert with constitutively active AKT to develop RS.Noteworthy, Cd19Cre;AKT-C double transgenic mice fail to develop leukemia and lymphoma, indicating that CLL development in Eµ:Tcl1 mice is a precondition to transformation. As for the downstream mechanisms of AKT-mediated transformation we identified GSK-3b inhibition and subsequent cMyc and Mcl-1 stabilization. This might confer contribute to resistance of RS cells against DNA-damaging and PI3K-inhibiting compounds in this novel model of Richter´s syndrome.
Conclusion
Collectively, we have generated the first murine Richter´s Syndrome model providing novel mechanistic insights into the molecular understanding of Richter's transformation as an AKT-driven disease. The new model is amenable to model therapeutic strategies and to address the efficacy of synergistic treatment combinations in transformed lymphoma.
Session topic: CLL natural history and progression
Keyword(s): Akt, Mouse model, Signal transduction, Transformation
Abstract: S118
Type: Oral Presentation
Presentation during EHA21: On Friday, June 10, 2016 from 12:30 - 12:45
Location: Auditorium 2
Background
Richter's syndrome (RS) is an aggressive transformation of Chronic Lymphocytic Leukemia (CLL) refractory to current therapies with dismal prognosis. RS arises from CLL cells independent of common DLBCL-mutations. Frequently mutations in p53, CDKN2 or cMyc genes are involved, but a significant proportion displays no specifically acquired driver mutation.
Aims
Here we aim to elucidate the role of AKT in transformation towards Richter´s syndrome in human patients and functionally address constitutively AKT-activation in vivo. Ultimately, we aim to develop mouse models that can be used to develop novel treatment options towards Richter´s syndrome.
Methods
FFPE sections of Richter syndrome patients were used for pAKT staining. We have developed a mouse model allowing for Cre-activatable expression of a myristoylated AKT constitutive active allele from the Rosa26 locus (AKT-C). We crossed that mice with Cd19Cre- and Cg1Cre-mediated B cell-specific AKT-C expression in the Eµ:Tcl1 CLL mouse model.
Results
In biopsies revealed from patients with RS one third of cases showed enhanced AKT activation. Strikingly, Richter's transformation was recapitulated when AKT was genetically over-activated in Eµ-Tcl-1 mice, where AKT-C expressing cells developed a high-grade lymphoma phenotype leading to significantly decreased survival. AKT-C expression in TCL1 mouse model CLL cells furthermore induced morphology changes displaying features of aggressive lymphoma such as large transformed B-cell phenotype and frequent mitotic figures, enhanced proliferation indicated by KI67. The phenotype of transformed aggressive lymphoma could be revealed independently in both Cd19Cre- and Cg1Cre-mediated activation of AKT. Thus, Eµ:Tcl1 transformed CLL cells act in concert with constitutively active AKT to develop RS.Noteworthy, Cd19Cre;AKT-C double transgenic mice fail to develop leukemia and lymphoma, indicating that CLL development in Eµ:Tcl1 mice is a precondition to transformation. As for the downstream mechanisms of AKT-mediated transformation we identified GSK-3b inhibition and subsequent cMyc and Mcl-1 stabilization. This might confer contribute to resistance of RS cells against DNA-damaging and PI3K-inhibiting compounds in this novel model of Richter´s syndrome.
Conclusion
Collectively, we have generated the first murine Richter´s Syndrome model providing novel mechanistic insights into the molecular understanding of Richter's transformation as an AKT-driven disease. The new model is amenable to model therapeutic strategies and to address the efficacy of synergistic treatment combinations in transformed lymphoma.
Session topic: CLL natural history and progression
Keyword(s): Akt, Mouse model, Signal transduction, Transformation
Type: Oral Presentation
Presentation during EHA21: On Friday, June 10, 2016 from 12:30 - 12:45
Location: Auditorium 2
Background
Richter's syndrome (RS) is an aggressive transformation of Chronic Lymphocytic Leukemia (CLL) refractory to current therapies with dismal prognosis. RS arises from CLL cells independent of common DLBCL-mutations. Frequently mutations in p53, CDKN2 or cMyc genes are involved, but a significant proportion displays no specifically acquired driver mutation.
Aims
Here we aim to elucidate the role of AKT in transformation towards Richter´s syndrome in human patients and functionally address constitutively AKT-activation in vivo. Ultimately, we aim to develop mouse models that can be used to develop novel treatment options towards Richter´s syndrome.
Methods
FFPE sections of Richter syndrome patients were used for pAKT staining. We have developed a mouse model allowing for Cre-activatable expression of a myristoylated AKT constitutive active allele from the Rosa26 locus (AKT-C). We crossed that mice with Cd19Cre- and Cg1Cre-mediated B cell-specific AKT-C expression in the Eµ:Tcl1 CLL mouse model.
Results
In biopsies revealed from patients with RS one third of cases showed enhanced AKT activation. Strikingly, Richter's transformation was recapitulated when AKT was genetically over-activated in Eµ-Tcl-1 mice, where AKT-C expressing cells developed a high-grade lymphoma phenotype leading to significantly decreased survival. AKT-C expression in TCL1 mouse model CLL cells furthermore induced morphology changes displaying features of aggressive lymphoma such as large transformed B-cell phenotype and frequent mitotic figures, enhanced proliferation indicated by KI67. The phenotype of transformed aggressive lymphoma could be revealed independently in both Cd19Cre- and Cg1Cre-mediated activation of AKT. Thus, Eµ:Tcl1 transformed CLL cells act in concert with constitutively active AKT to develop RS.Noteworthy, Cd19Cre;AKT-C double transgenic mice fail to develop leukemia and lymphoma, indicating that CLL development in Eµ:Tcl1 mice is a precondition to transformation. As for the downstream mechanisms of AKT-mediated transformation we identified GSK-3b inhibition and subsequent cMyc and Mcl-1 stabilization. This might confer contribute to resistance of RS cells against DNA-damaging and PI3K-inhibiting compounds in this novel model of Richter´s syndrome.
Conclusion
Collectively, we have generated the first murine Richter´s Syndrome model providing novel mechanistic insights into the molecular understanding of Richter's transformation as an AKT-driven disease. The new model is amenable to model therapeutic strategies and to address the efficacy of synergistic treatment combinations in transformed lymphoma.
Session topic: CLL natural history and progression
Keyword(s): Akt, Mouse model, Signal transduction, Transformation
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