IN MANTLE CELL LYMPHOMA, BCR SIGNALING AND WNT PATHWAY INDUCE Β-CATENIN STABILIZATION AND CELLULAR RE-LOCALIZATION BY DIFFERENT MECHANISMS.
(Abstract release date: 05/19/16)
EHA Library. Lazarian G. 06/09/16; 132942; E1393
Dr. Gregory Lazarian
Contributions
Contributions
Abstract
Abstract: E1393
Type: Eposter Presentation
Background
Mantle cell lymphoma (MCL) cells survival relies on the B-cell receptor (BCR) signaling pathway that also facilitates the interactions with the microenvironment. In more than 50% of MCL cases, the Wnt/β-catenin pathway is activated and contributes to cyclin D1 and c-myc expression. As both pathways are important for cell survival as well as tumor cell adhesion, we hypothesized that a cross talk between BCR signaling and β-catenin could affect the cell homeostasis and could be targeted by specific inhibitors.
Aims
The aim of the project is to identify the role of β-catenin in MCL and how it is activated. In parallel, the inhibition of a cross talk between the BCR signaling and the Wnt pathway by ibrutinib is analysed.
Methods
Peripheral blood B cells from MCL patients (n=8) were pretreated with Wnt/ β-catenin inhibitors: XAV-939 (25 μM), promoting degradation of β-catenin through the Axin dependent destruction complex or PKF118-310 (500 nM) blocking the interaction of β-catenin with the transcription factor TCF4. Cells were pre-treated with quercetine (20µM) a PI3K inhibitor, or Ibrutinib (5µM) a BTK inhibitor. BCR signaling pathway was then stimulated with soluble anti-IgM (10 mg/ml). As a control, Wnt/β-catenin pathway was activated by the conditioned media from human bone marrow stromal cells secreting large amount of Wnts. Apoptosis, β-catenin -dependent genes expression and β-catenin subcellular localization were analyzed by flow cytometry, RT-qPCR and cell fractionation respectively.
Results
β-catenin expression is detected in all leukemic MCL samples in variable amount. The inhibition of β-catenin/TCF transcriptional complex by PKF118-330 induces tumor cells apoptosis, suggesting an important contribution of β-catenin to MCL cell survival. In parallel, β-catenin level increases rapidly in response to BCR stimulation and this stabilization is inhibited by a pretreatment with Ibrutinib showing the existence of a cross talk between these two survival pathways. Wnt stimulation stabilizes β-catenin and its translocation into the nucleus leads to an increase of the target genes i.e. axin2, cyclin D1 and LEF1. After BCR stimulation, even though β-catenin rapidly translocates into the nucleus it does not induce the same transcriptional response, suggesting a different role of β-catenin when activated by BCR or Wnt. Moreover, stabilization of β-catenin degradation complex by a pretreatment with XAV939 does not induce its degradation after BCR stimulation suggesting that BCR signaling interferes with the β-catenin degradation process. Thus, the impact on β-catenin by BCR signaling is likely independent from Wnt.
Conclusion
The BCR signaling pathway leads to β-catenin stabilization and nuclear translocation. However, this nuclear translocation translates into a different transcriptional response than the one induced by Wnt. Most likely, β-catenin associates with different nuclear partners driving the expression or repression of BCR specific genes. Since β-catenin can stabilize cell adhesion structures, β-catenin likely represents another player through which the BCR signaling impacts on the interaction of MCL cells with the microenvironment. Importantly, this cross talk can be efficiently interrupted by Ibrutinib, currently used in mantle cell lymphoma treatment.
Session topic: E-poster
Keyword(s): Beta-catenin, Mantle cell lymphoma, Signaling, Wnt
Type: Eposter Presentation
Background
Mantle cell lymphoma (MCL) cells survival relies on the B-cell receptor (BCR) signaling pathway that also facilitates the interactions with the microenvironment. In more than 50% of MCL cases, the Wnt/β-catenin pathway is activated and contributes to cyclin D1 and c-myc expression. As both pathways are important for cell survival as well as tumor cell adhesion, we hypothesized that a cross talk between BCR signaling and β-catenin could affect the cell homeostasis and could be targeted by specific inhibitors.
Aims
The aim of the project is to identify the role of β-catenin in MCL and how it is activated. In parallel, the inhibition of a cross talk between the BCR signaling and the Wnt pathway by ibrutinib is analysed.
Methods
Peripheral blood B cells from MCL patients (n=8) were pretreated with Wnt/ β-catenin inhibitors: XAV-939 (25 μM), promoting degradation of β-catenin through the Axin dependent destruction complex or PKF118-310 (500 nM) blocking the interaction of β-catenin with the transcription factor TCF4. Cells were pre-treated with quercetine (20µM) a PI3K inhibitor, or Ibrutinib (5µM) a BTK inhibitor. BCR signaling pathway was then stimulated with soluble anti-IgM (10 mg/ml). As a control, Wnt/β-catenin pathway was activated by the conditioned media from human bone marrow stromal cells secreting large amount of Wnts. Apoptosis, β-catenin -dependent genes expression and β-catenin subcellular localization were analyzed by flow cytometry, RT-qPCR and cell fractionation respectively.
Results
β-catenin expression is detected in all leukemic MCL samples in variable amount. The inhibition of β-catenin/TCF transcriptional complex by PKF118-330 induces tumor cells apoptosis, suggesting an important contribution of β-catenin to MCL cell survival. In parallel, β-catenin level increases rapidly in response to BCR stimulation and this stabilization is inhibited by a pretreatment with Ibrutinib showing the existence of a cross talk between these two survival pathways. Wnt stimulation stabilizes β-catenin and its translocation into the nucleus leads to an increase of the target genes i.e. axin2, cyclin D1 and LEF1. After BCR stimulation, even though β-catenin rapidly translocates into the nucleus it does not induce the same transcriptional response, suggesting a different role of β-catenin when activated by BCR or Wnt. Moreover, stabilization of β-catenin degradation complex by a pretreatment with XAV939 does not induce its degradation after BCR stimulation suggesting that BCR signaling interferes with the β-catenin degradation process. Thus, the impact on β-catenin by BCR signaling is likely independent from Wnt.
Conclusion
The BCR signaling pathway leads to β-catenin stabilization and nuclear translocation. However, this nuclear translocation translates into a different transcriptional response than the one induced by Wnt. Most likely, β-catenin associates with different nuclear partners driving the expression or repression of BCR specific genes. Since β-catenin can stabilize cell adhesion structures, β-catenin likely represents another player through which the BCR signaling impacts on the interaction of MCL cells with the microenvironment. Importantly, this cross talk can be efficiently interrupted by Ibrutinib, currently used in mantle cell lymphoma treatment.
Session topic: E-poster
Keyword(s): Beta-catenin, Mantle cell lymphoma, Signaling, Wnt
Abstract: E1393
Type: Eposter Presentation
Background
Mantle cell lymphoma (MCL) cells survival relies on the B-cell receptor (BCR) signaling pathway that also facilitates the interactions with the microenvironment. In more than 50% of MCL cases, the Wnt/β-catenin pathway is activated and contributes to cyclin D1 and c-myc expression. As both pathways are important for cell survival as well as tumor cell adhesion, we hypothesized that a cross talk between BCR signaling and β-catenin could affect the cell homeostasis and could be targeted by specific inhibitors.
Aims
The aim of the project is to identify the role of β-catenin in MCL and how it is activated. In parallel, the inhibition of a cross talk between the BCR signaling and the Wnt pathway by ibrutinib is analysed.
Methods
Peripheral blood B cells from MCL patients (n=8) were pretreated with Wnt/ β-catenin inhibitors: XAV-939 (25 μM), promoting degradation of β-catenin through the Axin dependent destruction complex or PKF118-310 (500 nM) blocking the interaction of β-catenin with the transcription factor TCF4. Cells were pre-treated with quercetine (20µM) a PI3K inhibitor, or Ibrutinib (5µM) a BTK inhibitor. BCR signaling pathway was then stimulated with soluble anti-IgM (10 mg/ml). As a control, Wnt/β-catenin pathway was activated by the conditioned media from human bone marrow stromal cells secreting large amount of Wnts. Apoptosis, β-catenin -dependent genes expression and β-catenin subcellular localization were analyzed by flow cytometry, RT-qPCR and cell fractionation respectively.
Results
β-catenin expression is detected in all leukemic MCL samples in variable amount. The inhibition of β-catenin/TCF transcriptional complex by PKF118-330 induces tumor cells apoptosis, suggesting an important contribution of β-catenin to MCL cell survival. In parallel, β-catenin level increases rapidly in response to BCR stimulation and this stabilization is inhibited by a pretreatment with Ibrutinib showing the existence of a cross talk between these two survival pathways. Wnt stimulation stabilizes β-catenin and its translocation into the nucleus leads to an increase of the target genes i.e. axin2, cyclin D1 and LEF1. After BCR stimulation, even though β-catenin rapidly translocates into the nucleus it does not induce the same transcriptional response, suggesting a different role of β-catenin when activated by BCR or Wnt. Moreover, stabilization of β-catenin degradation complex by a pretreatment with XAV939 does not induce its degradation after BCR stimulation suggesting that BCR signaling interferes with the β-catenin degradation process. Thus, the impact on β-catenin by BCR signaling is likely independent from Wnt.
Conclusion
The BCR signaling pathway leads to β-catenin stabilization and nuclear translocation. However, this nuclear translocation translates into a different transcriptional response than the one induced by Wnt. Most likely, β-catenin associates with different nuclear partners driving the expression or repression of BCR specific genes. Since β-catenin can stabilize cell adhesion structures, β-catenin likely represents another player through which the BCR signaling impacts on the interaction of MCL cells with the microenvironment. Importantly, this cross talk can be efficiently interrupted by Ibrutinib, currently used in mantle cell lymphoma treatment.
Session topic: E-poster
Keyword(s): Beta-catenin, Mantle cell lymphoma, Signaling, Wnt
Type: Eposter Presentation
Background
Mantle cell lymphoma (MCL) cells survival relies on the B-cell receptor (BCR) signaling pathway that also facilitates the interactions with the microenvironment. In more than 50% of MCL cases, the Wnt/β-catenin pathway is activated and contributes to cyclin D1 and c-myc expression. As both pathways are important for cell survival as well as tumor cell adhesion, we hypothesized that a cross talk between BCR signaling and β-catenin could affect the cell homeostasis and could be targeted by specific inhibitors.
Aims
The aim of the project is to identify the role of β-catenin in MCL and how it is activated. In parallel, the inhibition of a cross talk between the BCR signaling and the Wnt pathway by ibrutinib is analysed.
Methods
Peripheral blood B cells from MCL patients (n=8) were pretreated with Wnt/ β-catenin inhibitors: XAV-939 (25 μM), promoting degradation of β-catenin through the Axin dependent destruction complex or PKF118-310 (500 nM) blocking the interaction of β-catenin with the transcription factor TCF4. Cells were pre-treated with quercetine (20µM) a PI3K inhibitor, or Ibrutinib (5µM) a BTK inhibitor. BCR signaling pathway was then stimulated with soluble anti-IgM (10 mg/ml). As a control, Wnt/β-catenin pathway was activated by the conditioned media from human bone marrow stromal cells secreting large amount of Wnts. Apoptosis, β-catenin -dependent genes expression and β-catenin subcellular localization were analyzed by flow cytometry, RT-qPCR and cell fractionation respectively.
Results
β-catenin expression is detected in all leukemic MCL samples in variable amount. The inhibition of β-catenin/TCF transcriptional complex by PKF118-330 induces tumor cells apoptosis, suggesting an important contribution of β-catenin to MCL cell survival. In parallel, β-catenin level increases rapidly in response to BCR stimulation and this stabilization is inhibited by a pretreatment with Ibrutinib showing the existence of a cross talk between these two survival pathways. Wnt stimulation stabilizes β-catenin and its translocation into the nucleus leads to an increase of the target genes i.e. axin2, cyclin D1 and LEF1. After BCR stimulation, even though β-catenin rapidly translocates into the nucleus it does not induce the same transcriptional response, suggesting a different role of β-catenin when activated by BCR or Wnt. Moreover, stabilization of β-catenin degradation complex by a pretreatment with XAV939 does not induce its degradation after BCR stimulation suggesting that BCR signaling interferes with the β-catenin degradation process. Thus, the impact on β-catenin by BCR signaling is likely independent from Wnt.
Conclusion
The BCR signaling pathway leads to β-catenin stabilization and nuclear translocation. However, this nuclear translocation translates into a different transcriptional response than the one induced by Wnt. Most likely, β-catenin associates with different nuclear partners driving the expression or repression of BCR specific genes. Since β-catenin can stabilize cell adhesion structures, β-catenin likely represents another player through which the BCR signaling impacts on the interaction of MCL cells with the microenvironment. Importantly, this cross talk can be efficiently interrupted by Ibrutinib, currently used in mantle cell lymphoma treatment.
Session topic: E-poster
Keyword(s): Beta-catenin, Mantle cell lymphoma, Signaling, Wnt
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