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2.9 Pro-Survival Signalling in ‘Responder' CLL Cells After Ligation of CD180
Abstracts 2.8 CXCL12 Is a Costimulator for CD4ⴙ T-Cell Activation and Proliferation in Patients with Chronic Lymphocytic Leukemia Mercedes Borge,1,2 Paula Romina Nannini,1,2 Pablo Elías Morande,1,2 Carolina Jancic,1,2 Samanta Romina Zanetti,1 Alicia Bistmans,3 Raimundo Fernando Bezares,4 Mirta Giordano,1,2 Romina Gamberale1,2 1
Laboratorio de Inmunología Oncológica, Academia Nacional de
Medicina, Buenos Aires, Argentina; 2Departamento de Microbiología, Parasitología e Inmunología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina; 3Hospital Ramos Mejía, Buenos Aires, Argentina; 4Hospital T. Álvarez y Hospital Bancario, Buenos Aires, Argentina
B-cell chronic lymphocytic leukemia (CLL) cells proliferate in lymphoid tissues in close contact with activated T cells, stromal cells, and accessory myeloid cells, such as nurse-like cells (NLC), which favor CLL cell survival and proliferation.1–3 CXCL12 is a highly conserved chemokine produced by stromal cells and NLC;3 CXCR4, its main receptor, was shown to induce CLL4 and T-cell migration5 and leukemic cell activation and survival4. The aim of this study was to determine whether CXCL12 enhances activation and proliferation of T cells in patients with CLL. Peripheral blood mononuclear cells from patients with CLL were cultured for 2 hours with or without recombinant human CXCL12 (rhCXCL12), then transferred to cell culture plates with immobilized anti-CD3 monoclonal antibodies (mAb). After 24 hours of culture, expression of the activation markers CD25, CD69, and CD154 on CD4⫹ T cells was evaluated by fluorescence-activated cell sorting. We found that the combination of anti-CD3 and rhCXCL12 significantly increased the expression of all activation markers beyond that induced by anti-CD3 alone (p ⬍ 0.01, n ⫽ 18). No significant differences were observed when samples were segregated according to ZAP-70 or CD38 expression. The CXCL12-mediated enhancement of CD4⫹ T-cell activation was similarly observed when we performed the experiments with purified T cells and was blocked by anti-CXCR4 mAb, suggesting that this receptor is necessary for T-cell costimulation by CXCL12. Moreover, we found that rhCXCL12 enhances interferon-␥ production (p ⬍ 0.01, n ⫽ 18) and proliferation (p ⬍ 0.01, n ⫽ 10) of activated CD4⫹ T cells from patients with CLL beyond that induced by anti-CD3 alone. Of note, leukemic cell activation (p ⬍ 0.05, n ⫽ 10) and proliferation (p ⬍ 0.05, n ⫽ 10) were enhanced by activated T cells in the presence of rhCXCL12. In addition, autologous NLC increased the activation (p ⬍ 0.01, n ⫽ 10) and proliferation (p ⬍ 0.05, n ⫽ 5) of CD4⫹ T cells from patients with CLL, in part through a CXCR4-dependent mechanism. Our results prompted us to hypothesize that CXCL2 production by the lymphoid tissue microenvironment in CLL patients may play a key dual role for T-cell physiology, functioning not only as a chemoattractant5 but also as a costimulatory factor for activated T cells. Because it was clearly demonstrated that the activation of T cells from patients with CLL is critical in the disease,6 identifying the mechanisms whereby T cells
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respond to microenvironmental activating and proliferating signals could reveal novel targets for therapy.
References 1. 2. 3. 4. 5.
Ghia et al. Curr Top Microbiol Immunol 2005;294:135. Caligaris-Cappio. Br J Haematol 2003;123:380. Burger et al. Blood 2000;96:2655. Burger and Kipps. Blood 2006;107:1761. Borge et al. CXCL12-induced chemotaxis is impaired in T cells from patients with ZAP-70-negative chronic lymphocytic leukemia. Haematologica 2010;95:768. 6. Bagnara et al. Blood 2011;117:5463
2.9 Pro-Survival Signalling in ‘Responder’ CLL Cells After Ligation of CD180 Nino Porakishvili,1 Peter M. Lydyard,1 Ketki Vispute,1 Azka Memon,1 Andrew Steele,2 Nina Kulikova,3 Amit Nathwani,4 Kanti R. Rai,5 Rajendra N. Damle,5 Edward A. Clark,6 Nicholas Chiorazzi5 1
School of Life Sciences, University of Westminster, London, United Kingdom; 2University of Southampton, Southampton, United Kingdom; 3Javakhishvili Tbilisi State University, Tbilisi, Georgia; 4 UCL Cancer Institute, London, United Kingdom; 5The Feinstein Institute for Medical Research, Manhasset, NY; 6University of Washington, Seattle, WA
Introduction: The role of the microenvironment in the development and progression of chronic lymphocytic leukaemia (CLL) is currently of major interest. Pathogen- and damage-associated molecular patterns represent exogenous and endogenous microenvironmental factors acting via a range of receptors, including Toll-like receptors (TLRs). CD180/RP105 is a membrane-associated orphan receptor that belongs to the TLR family, is expressed by professional antigen-presenting cells, and drives normal B-cell activation and proliferation. We previously showed that approximately 60% of CLL clones expressed surface CD180,1 but only one half of these clones responded to ligation with anti-CD180 monoclonal antibody (mAb), resulting in activation, cycling, and reduced basal apoptosis. This was similar or superior to that induced by anti-CD40 mAb or interleukin-4.1,2 These CLL clones upregulated CD86 and Ki-67 upon stimulation with anti-CD180 mAb and were termed ‘responders’ (R). In contrast, CD180⫹CLL samples that did not respond to anti-CD180 mAb, despite expressing a high density of CD180 receptors, were termed ‘nonresponders’ (NR).2 We demonstrated that in R-CLL cells, treatment with anti-CD180 mAb significantly induced phosphorylation of ZAP70/Syk, Erk, p38MAPK, and Akt in a Ca2⫹-independent manner compared with untreated cells. In contrast, CD180-mediated signalling in NR-CLL cells did not progress downstream from ZAP70/Syk phosphorylation, indicating a block in activation of downstream protein kinases and possible anergy.2 We further studied CD180-mediated pro-survival signalling in RCLL cells. Methods: Fourteen R-CLL clones were stimulated with anti-CD180 for intervals of 30 minutes to 24 hours. Cells were stained with anti-CD19-PE/Cy5 mAb, fixed, permeabilized, counterstained with mAbs to phosphorylated intracellular protein kinases ZAP70/Syk (PE) and Akt (fluorescein isothiocyanate), and analyzed by flow cytometry. Immunoblotting was performed to confirm the data, and to analyze the levels of phospho-PI3Kp85 and phospho-
Abstracts NFB and antiapoptotic proteins Mcl1-1, Bcl-XL, and Bcl-2. Results: The R-CLL clones differed in the speed of signal transduction downstream to Akt, thus identifying early responders (ER) (30minute stimulation) and late responders (LR) (24-hour stimulation). The ER-CLL cells expressed significantly higher density of CD79b than LR-CLL cells: 2273 ⫾ 1664 vs 760 ⫾ 532 antibody relative binding sites/cell (p ⫽ 0.039). The ER were also enriched for IgM⫹ cells compared with LR: 66.2% ⫾ 13.1% vs 32.3% ⫾ 31.1% (p ⫽ 0.022), indicating involvement of IgM/CD79b in CD180 signal transduction. Regardless of category, an increase in phosphorylated Akt was seen in all R-CLL cells, and we now consider activation of Akt to be a more precise indicator of R-CLL type than the previously suggested CD86 upregulation. Of note, CD180 ligation led to increased levels of phosphorylated PI3Kp85, which suggested activation of the PI3K-Akt (PKB) pathway. Involvement of PI3K is in line with the lack of Ca2⫹ flux in CLL cells after CD180 ligation.2 We also demonstrated that whilst Bcl-2 and Bcl-XL were constitutively expressed, ligation with anti-CD180 mAb did not result in changes to protein expression. However, activation of CD180 significantly increased levels of Mcl-1. Conclusion: Pro-survival signalling in CLL clones responsive to CD180 ligation operates via activation of a ZAP70/Syk–PI3K/Akt pathway and upregulation of Mcl-1. The reasons for differences in the rate of signalling downstream of Akt are unclear and currently under investigation.
References 1. Porakishvili et al. Br J Haematol 2005;131:313. 2. Porakishvili et al. Br J Haematol 2011;153:486.
2.10 Effect of Sequential Ligation of CD180/RP105 and sIgM on Downstream Signalling in CLL Cells Ketki Vispute,1 Nino Porakishvili,1 Andrew Steele,2 Amit Nathwani,3 Rajendra Damle,4 Edward A. Clark,5 Kanti R. Rai,4 Nicholas Chiorazzi,4 Peter M. Lydyard1
noglobulin M (sIgM).2 In this study, we investigated the effect of interaction between CD180 and sIgM on transduction of intracellular signalling in R-CLL cells. Methods: R-CLL clones from 22 CLL patients were stimulated with anti-CD180 mAb for 30 minutes, and then with F(ab’)2 fragments of goat anti-human IgM antibodies for another 30 minutes. Stimulation with either antibody alone or unstimulated cultures was used as control. Cells were stained with anti-CD19⬃PE/Cy5 mAb, fixed, permeabilized, counterstained with mAb (fluorescein isothiocyanate) to pAkt, and analysed by flow cytometry. Immunoblotting was used in several cases to determine the levels of pAkt, phosphorylated PI3Kp85, total Akt and PI3Kp85 and antiapoptotic proteins Mcl-1 and Bcl-XL. Results: Ligation of CD180 and sIgM measured by activation of Akt was heterogeneous, but the proportions of pAkt⫹ cells were significantly greater than those of unstimulated cultures, at 25.3% ⫾ 9.3% (CD180: 40.2% ⫾ 22.5% [range 9.1%–93.4%, p ⫽ 0.0034]; IgM: 41.8% ⫾ 20.4% [range 6.0%– 86.6%, p ⫽ 0.001] compared with unstimulated cultures). However, the percentages of pAkt⫹ cells after sequential ligation of CD180 and sIgM decreased significantly down to basal levels, compared with ligation of CD180 or sIgM alone (27.7% ⫾ 18.6%, p⫽0.048). A decrease in pAkt levels after sequential stimulation with anti-CD180 and anti-IgM Abs was confirmed by immunoblotting (Figure 1a), despite high levels of total Akt (Figure 1b). A simultaneous notable decrease in activation of PI3K (Figure 1c) after sequential stimulation was detected, whilst the levels of total PI3-K were intact (Figure 1d), suggesting that activation of the PI3K-Akt pathway was affected by the engagement of 2 receptors. We hypothesise that CD180 and sIgM operate via joint pathways which become anergic after 1 of the pathways is activated. No conclusive results were obtained regarding the effect of costimulation at the level of Mcl-1 and Bcl-XL. Conclusion: Engagement of sIgM abrogates CD180-mediated intracellular signalling via the PI3K-Akt pathway in CLL cells.
References 1. Porakishvili et al. Br J Haematol 2011;153:486. 2. Porakishvili et al. Haematologica 2009;94:S38.
1
School of Life Sciences, University of Westminster, London, United Kingdom; 2University of Southampton, Southampton, United Kingdom; 3UCL Cancer Institute, London, United Kingdom; 4The Feinstein Institute for Medical Research, Manhasset, NY; 5University of Washington, Seattle, WA
Introduction: We previously demonstrated that intracellular signalling induced in CLL and in control B-cells through ligation of CD180/RP105 – an orphan receptor of the Toll-like receptor family – is operating via pathways associated with BCR signalling.1 Approximately one half of CD180⫹ CLL clones were responsive to CD180 ligation by monoclonal antibody (mAb) as assessed by activation, cycling, reduced basal apoptosis, and downstream signalling via PI3K/Akt; these were termed ‘responders’ (R-CLL).1 Levels of phosphorylated Akt (pAkt) seemed to be a key indicator of pro-survival signalling via CD180 as well as a delineator of responder versus nonresponder CLL clones.2 In a separate study, we showed that pretreatment of R-CLL cells, but not control B-cells, with antiCD180 mAb led to a decrease in signalling intensity, particularly through Akt, mediated by subsequent engagement of surface immu-
2.11 Chronic Lymphocytic Leukemia Cells Respond to CD180 Ligation by Alternative Signalling via Akt (PKB) or P38MAPK Pathways Nino Porakishvili,1 Peter M. Lydyard,1 Ketki Vispute,1 Iselin Kornli,1 Andrew Steele,2 Amit Nathwani,3 Kanti R. Rai,4 Rajendra N. Damle,4 Edward A. Clark,5 Nicholas Chiorazzi4 1
School of Life Sciences, University of Westminster, London, United Kingdom; 2University of Southampton, Southampton, United Kingdom; 3UCL Cancer Institute, London, United Kingdom; 4The Feinstein Institute for Medical Research, Manhasset, NY; 5University of Washington, Seattle, WA
Introduction: We previously showed that approximately one half of CLL clones expressing CD180/RP105, a membrane-associated orphan receptor of the Toll-like receptor family, respond to ligation with anti-CD180 monoclonal antibody (mAb) by activation, prolif-
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Laboratorio de Inmunología Oncológica, Academia Nacional de
Medicina, Buenos Aires, Argentina; 2Departamento de Microbiología, Parasitología e Inmunología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina; 3Hospital Ramos Mejía, Buenos Aires, Argentina; 4Hospital T. Álvarez y Hospital Bancario, Buenos Aires, Argentina
B-cell chronic lymphocytic leukemia (CLL) cells proliferate in lymphoid tissues in close contact with activated T cells, stromal cells, and accessory myeloid cells, such as nurse-like cells (NLC), which favor CLL cell survival and proliferation.1–3 CXCL12 is a highly conserved chemokine produced by stromal cells and NLC;3 CXCR4, its main receptor, was shown to induce CLL4 and T-cell migration5 and leukemic cell activation and survival4. The aim of this study was to determine whether CXCL12 enhances activation and proliferation of T cells in patients with CLL. Peripheral blood mononuclear cells from patients with CLL were cultured for 2 hours with or without recombinant human CXCL12 (rhCXCL12), then transferred to cell culture plates with immobilized anti-CD3 monoclonal antibodies (mAb). After 24 hours of culture, expression of the activation markers CD25, CD69, and CD154 on CD4⫹ T cells was evaluated by fluorescence-activated cell sorting. We found that the combination of anti-CD3 and rhCXCL12 significantly increased the expression of all activation markers beyond that induced by anti-CD3 alone (p ⬍ 0.01, n ⫽ 18). No significant differences were observed when samples were segregated according to ZAP-70 or CD38 expression. The CXCL12-mediated enhancement of CD4⫹ T-cell activation was similarly observed when we performed the experiments with purified T cells and was blocked by anti-CXCR4 mAb, suggesting that this receptor is necessary for T-cell costimulation by CXCL12. Moreover, we found that rhCXCL12 enhances interferon-␥ production (p ⬍ 0.01, n ⫽ 18) and proliferation (p ⬍ 0.01, n ⫽ 10) of activated CD4⫹ T cells from patients with CLL beyond that induced by anti-CD3 alone. Of note, leukemic cell activation (p ⬍ 0.05, n ⫽ 10) and proliferation (p ⬍ 0.05, n ⫽ 10) were enhanced by activated T cells in the presence of rhCXCL12. In addition, autologous NLC increased the activation (p ⬍ 0.01, n ⫽ 10) and proliferation (p ⬍ 0.05, n ⫽ 5) of CD4⫹ T cells from patients with CLL, in part through a CXCR4-dependent mechanism. Our results prompted us to hypothesize that CXCL2 production by the lymphoid tissue microenvironment in CLL patients may play a key dual role for T-cell physiology, functioning not only as a chemoattractant5 but also as a costimulatory factor for activated T cells. Because it was clearly demonstrated that the activation of T cells from patients with CLL is critical in the disease,6 identifying the mechanisms whereby T cells
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respond to microenvironmental activating and proliferating signals could reveal novel targets for therapy.
References 1. 2. 3. 4. 5.
Ghia et al. Curr Top Microbiol Immunol 2005;294:135. Caligaris-Cappio. Br J Haematol 2003;123:380. Burger et al. Blood 2000;96:2655. Burger and Kipps. Blood 2006;107:1761. Borge et al. CXCL12-induced chemotaxis is impaired in T cells from patients with ZAP-70-negative chronic lymphocytic leukemia. Haematologica 2010;95:768. 6. Bagnara et al. Blood 2011;117:5463
2.9 Pro-Survival Signalling in ‘Responder’ CLL Cells After Ligation of CD180 Nino Porakishvili,1 Peter M. Lydyard,1 Ketki Vispute,1 Azka Memon,1 Andrew Steele,2 Nina Kulikova,3 Amit Nathwani,4 Kanti R. Rai,5 Rajendra N. Damle,5 Edward A. Clark,6 Nicholas Chiorazzi5 1
School of Life Sciences, University of Westminster, London, United Kingdom; 2University of Southampton, Southampton, United Kingdom; 3Javakhishvili Tbilisi State University, Tbilisi, Georgia; 4 UCL Cancer Institute, London, United Kingdom; 5The Feinstein Institute for Medical Research, Manhasset, NY; 6University of Washington, Seattle, WA
Introduction: The role of the microenvironment in the development and progression of chronic lymphocytic leukaemia (CLL) is currently of major interest. Pathogen- and damage-associated molecular patterns represent exogenous and endogenous microenvironmental factors acting via a range of receptors, including Toll-like receptors (TLRs). CD180/RP105 is a membrane-associated orphan receptor that belongs to the TLR family, is expressed by professional antigen-presenting cells, and drives normal B-cell activation and proliferation. We previously showed that approximately 60% of CLL clones expressed surface CD180,1 but only one half of these clones responded to ligation with anti-CD180 monoclonal antibody (mAb), resulting in activation, cycling, and reduced basal apoptosis. This was similar or superior to that induced by anti-CD40 mAb or interleukin-4.1,2 These CLL clones upregulated CD86 and Ki-67 upon stimulation with anti-CD180 mAb and were termed ‘responders’ (R). In contrast, CD180⫹CLL samples that did not respond to anti-CD180 mAb, despite expressing a high density of CD180 receptors, were termed ‘nonresponders’ (NR).2 We demonstrated that in R-CLL cells, treatment with anti-CD180 mAb significantly induced phosphorylation of ZAP70/Syk, Erk, p38MAPK, and Akt in a Ca2⫹-independent manner compared with untreated cells. In contrast, CD180-mediated signalling in NR-CLL cells did not progress downstream from ZAP70/Syk phosphorylation, indicating a block in activation of downstream protein kinases and possible anergy.2 We further studied CD180-mediated pro-survival signalling in RCLL cells. Methods: Fourteen R-CLL clones were stimulated with anti-CD180 for intervals of 30 minutes to 24 hours. Cells were stained with anti-CD19-PE/Cy5 mAb, fixed, permeabilized, counterstained with mAbs to phosphorylated intracellular protein kinases ZAP70/Syk (PE) and Akt (fluorescein isothiocyanate), and analyzed by flow cytometry. Immunoblotting was performed to confirm the data, and to analyze the levels of phospho-PI3Kp85 and phospho-
Abstracts NFB and antiapoptotic proteins Mcl1-1, Bcl-XL, and Bcl-2. Results: The R-CLL clones differed in the speed of signal transduction downstream to Akt, thus identifying early responders (ER) (30minute stimulation) and late responders (LR) (24-hour stimulation). The ER-CLL cells expressed significantly higher density of CD79b than LR-CLL cells: 2273 ⫾ 1664 vs 760 ⫾ 532 antibody relative binding sites/cell (p ⫽ 0.039). The ER were also enriched for IgM⫹ cells compared with LR: 66.2% ⫾ 13.1% vs 32.3% ⫾ 31.1% (p ⫽ 0.022), indicating involvement of IgM/CD79b in CD180 signal transduction. Regardless of category, an increase in phosphorylated Akt was seen in all R-CLL cells, and we now consider activation of Akt to be a more precise indicator of R-CLL type than the previously suggested CD86 upregulation. Of note, CD180 ligation led to increased levels of phosphorylated PI3Kp85, which suggested activation of the PI3K-Akt (PKB) pathway. Involvement of PI3K is in line with the lack of Ca2⫹ flux in CLL cells after CD180 ligation.2 We also demonstrated that whilst Bcl-2 and Bcl-XL were constitutively expressed, ligation with anti-CD180 mAb did not result in changes to protein expression. However, activation of CD180 significantly increased levels of Mcl-1. Conclusion: Pro-survival signalling in CLL clones responsive to CD180 ligation operates via activation of a ZAP70/Syk–PI3K/Akt pathway and upregulation of Mcl-1. The reasons for differences in the rate of signalling downstream of Akt are unclear and currently under investigation.
References 1. Porakishvili et al. Br J Haematol 2005;131:313. 2. Porakishvili et al. Br J Haematol 2011;153:486.
2.10 Effect of Sequential Ligation of CD180/RP105 and sIgM on Downstream Signalling in CLL Cells Ketki Vispute,1 Nino Porakishvili,1 Andrew Steele,2 Amit Nathwani,3 Rajendra Damle,4 Edward A. Clark,5 Kanti R. Rai,4 Nicholas Chiorazzi,4 Peter M. Lydyard1
noglobulin M (sIgM).2 In this study, we investigated the effect of interaction between CD180 and sIgM on transduction of intracellular signalling in R-CLL cells. Methods: R-CLL clones from 22 CLL patients were stimulated with anti-CD180 mAb for 30 minutes, and then with F(ab’)2 fragments of goat anti-human IgM antibodies for another 30 minutes. Stimulation with either antibody alone or unstimulated cultures was used as control. Cells were stained with anti-CD19⬃PE/Cy5 mAb, fixed, permeabilized, counterstained with mAb (fluorescein isothiocyanate) to pAkt, and analysed by flow cytometry. Immunoblotting was used in several cases to determine the levels of pAkt, phosphorylated PI3Kp85, total Akt and PI3Kp85 and antiapoptotic proteins Mcl-1 and Bcl-XL. Results: Ligation of CD180 and sIgM measured by activation of Akt was heterogeneous, but the proportions of pAkt⫹ cells were significantly greater than those of unstimulated cultures, at 25.3% ⫾ 9.3% (CD180: 40.2% ⫾ 22.5% [range 9.1%–93.4%, p ⫽ 0.0034]; IgM: 41.8% ⫾ 20.4% [range 6.0%– 86.6%, p ⫽ 0.001] compared with unstimulated cultures). However, the percentages of pAkt⫹ cells after sequential ligation of CD180 and sIgM decreased significantly down to basal levels, compared with ligation of CD180 or sIgM alone (27.7% ⫾ 18.6%, p⫽0.048). A decrease in pAkt levels after sequential stimulation with anti-CD180 and anti-IgM Abs was confirmed by immunoblotting (Figure 1a), despite high levels of total Akt (Figure 1b). A simultaneous notable decrease in activation of PI3K (Figure 1c) after sequential stimulation was detected, whilst the levels of total PI3-K were intact (Figure 1d), suggesting that activation of the PI3K-Akt pathway was affected by the engagement of 2 receptors. We hypothesise that CD180 and sIgM operate via joint pathways which become anergic after 1 of the pathways is activated. No conclusive results were obtained regarding the effect of costimulation at the level of Mcl-1 and Bcl-XL. Conclusion: Engagement of sIgM abrogates CD180-mediated intracellular signalling via the PI3K-Akt pathway in CLL cells.
References 1. Porakishvili et al. Br J Haematol 2011;153:486. 2. Porakishvili et al. Haematologica 2009;94:S38.
1
School of Life Sciences, University of Westminster, London, United Kingdom; 2University of Southampton, Southampton, United Kingdom; 3UCL Cancer Institute, London, United Kingdom; 4The Feinstein Institute for Medical Research, Manhasset, NY; 5University of Washington, Seattle, WA
Introduction: We previously demonstrated that intracellular signalling induced in CLL and in control B-cells through ligation of CD180/RP105 – an orphan receptor of the Toll-like receptor family – is operating via pathways associated with BCR signalling.1 Approximately one half of CD180⫹ CLL clones were responsive to CD180 ligation by monoclonal antibody (mAb) as assessed by activation, cycling, reduced basal apoptosis, and downstream signalling via PI3K/Akt; these were termed ‘responders’ (R-CLL).1 Levels of phosphorylated Akt (pAkt) seemed to be a key indicator of pro-survival signalling via CD180 as well as a delineator of responder versus nonresponder CLL clones.2 In a separate study, we showed that pretreatment of R-CLL cells, but not control B-cells, with antiCD180 mAb led to a decrease in signalling intensity, particularly through Akt, mediated by subsequent engagement of surface immu-
2.11 Chronic Lymphocytic Leukemia Cells Respond to CD180 Ligation by Alternative Signalling via Akt (PKB) or P38MAPK Pathways Nino Porakishvili,1 Peter M. Lydyard,1 Ketki Vispute,1 Iselin Kornli,1 Andrew Steele,2 Amit Nathwani,3 Kanti R. Rai,4 Rajendra N. Damle,4 Edward A. Clark,5 Nicholas Chiorazzi4 1
School of Life Sciences, University of Westminster, London, United Kingdom; 2University of Southampton, Southampton, United Kingdom; 3UCL Cancer Institute, London, United Kingdom; 4The Feinstein Institute for Medical Research, Manhasset, NY; 5University of Washington, Seattle, WA
Introduction: We previously showed that approximately one half of CLL clones expressing CD180/RP105, a membrane-associated orphan receptor of the Toll-like receptor family, respond to ligation with anti-CD180 monoclonal antibody (mAb) by activation, prolif-
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