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Modeling tumor-host interactions of chronic lymphocytic leukemia in xenografted mice to study tumor biology and evaluate targeted therapy.

Herman SE, Sun X, McAuley EM, Hsieh MM, Pittaluga S, Raffeld M, Liu D, Keyvanfar K, Chapman CM, Chen J, Buggy JJ, Aue G, Tisdale JF, Pérez-Galán P, Wiestner A - Leukemia (2013)

Bottom Line: We found that the murine spleen (SP) microenvironment supported CLL cell proliferation and activation to a similar degree than the human LN, including induction of BCR and NF-κB signaling in the xenografted cells.Next, we used this model to study ibrutinib, a Bruton's tyrosine kinase inhibitor in clinical development.Ibrutinib inhibited BCR and NF-κB signaling induced by the microenvironment, decreased proliferation, induced apoptosis and reduced the tumor burden in vivo.

View Article: PubMed Central - PubMed

Affiliation: Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA.

ABSTRACT
Chronic lymphocytic leukemia (CLL) cells depend on microenvironmental factors for proliferation and survival. In particular, the B-cell receptor (BCR) and nuclear factor- κB (NF-κB) pathways are activated in the lymph node (LN) microenvironment. Thus, model systems mimicking tumor-host interactions are important tools to study CLL biology and pathogenesis. We investigated whether the recently established NOD/scid/γc() (NSG) mouse xenograft model can recapitulate the effects of the human microenvironment. We assessed, therefore, tumor characteristics previously defined in LN-resident CLL cells, including proliferation, and activation of the BCR and NF-κB pathways. We found that the murine spleen (SP) microenvironment supported CLL cell proliferation and activation to a similar degree than the human LN, including induction of BCR and NF-κB signaling in the xenografted cells. Next, we used this model to study ibrutinib, a Bruton's tyrosine kinase inhibitor in clinical development. Ibrutinib inhibited BCR and NF-κB signaling induced by the microenvironment, decreased proliferation, induced apoptosis and reduced the tumor burden in vivo. Thus, our data demonstrate that the SP of xenografted NSG mice can, in part, recapitulate the role of the human LN for CLL cells. In addition, we show that ibrutinib effectively disrupts tumor-host interactions essential for CLL cell proliferation and survival in vivo.

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Expression of activation markers on CLL cells is increased in the tissue compartment. (a) Overlay histograms showing mean fluorescent intensity (MFI) for CD38, CD69, and CXCR4 (CD184) on xenografted CLL cells from the mouse spleen (SP) and PB. (b) NSG mice (n=13) injected with PBMCs from six different patients were sacrificed 3–4 weeks post xenografting. Each dot represents a sample from one mouse; lines connect PB and SP samples from the same mouse. (c) CLL cells in the mouse spleen (SP) and human lymph node (LN) upregulate activation markers and downregulate CXCR4 compared to circulating cells in the PB. Shown is the mean (± SEM) of the relative expression for the indicated cell surface markers calculated as the MFI ratio of xenografted CLL cells in mouse SP to mouse PB (open bars) and of CLL cells in human LN to human PB (black bars) obtained from 3 patients. Student's t-test was used to test for significance in all panels.
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Figure 2: Expression of activation markers on CLL cells is increased in the tissue compartment. (a) Overlay histograms showing mean fluorescent intensity (MFI) for CD38, CD69, and CXCR4 (CD184) on xenografted CLL cells from the mouse spleen (SP) and PB. (b) NSG mice (n=13) injected with PBMCs from six different patients were sacrificed 3–4 weeks post xenografting. Each dot represents a sample from one mouse; lines connect PB and SP samples from the same mouse. (c) CLL cells in the mouse spleen (SP) and human lymph node (LN) upregulate activation markers and downregulate CXCR4 compared to circulating cells in the PB. Shown is the mean (± SEM) of the relative expression for the indicated cell surface markers calculated as the MFI ratio of xenografted CLL cells in mouse SP to mouse PB (open bars) and of CLL cells in human LN to human PB (black bars) obtained from 3 patients. Student's t-test was used to test for significance in all panels.

Mentions: In keeping with observations in patients, we found that xenografted CLL cells in the murine spleen as compared to matched PB samples showed significantly increased expression of the activation markers CD38 and CD69 (Figure 2a-b, P = .03 and P < .001, respectively). Similarly, CLL cells in the murine spleen expressed less CXCR4 than circulating CLL cells (Figure 2a-b, P < .001), likely as a result of binding to its ligand CXCL12/SDF-1.


Modeling tumor-host interactions of chronic lymphocytic leukemia in xenografted mice to study tumor biology and evaluate targeted therapy.

Herman SE, Sun X, McAuley EM, Hsieh MM, Pittaluga S, Raffeld M, Liu D, Keyvanfar K, Chapman CM, Chen J, Buggy JJ, Aue G, Tisdale JF, Pérez-Galán P, Wiestner A - Leukemia (2013)

Expression of activation markers on CLL cells is increased in the tissue compartment. (a) Overlay histograms showing mean fluorescent intensity (MFI) for CD38, CD69, and CXCR4 (CD184) on xenografted CLL cells from the mouse spleen (SP) and PB. (b) NSG mice (n=13) injected with PBMCs from six different patients were sacrificed 3–4 weeks post xenografting. Each dot represents a sample from one mouse; lines connect PB and SP samples from the same mouse. (c) CLL cells in the mouse spleen (SP) and human lymph node (LN) upregulate activation markers and downregulate CXCR4 compared to circulating cells in the PB. Shown is the mean (± SEM) of the relative expression for the indicated cell surface markers calculated as the MFI ratio of xenografted CLL cells in mouse SP to mouse PB (open bars) and of CLL cells in human LN to human PB (black bars) obtained from 3 patients. Student's t-test was used to test for significance in all panels.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4126654&req=5

Figure 2: Expression of activation markers on CLL cells is increased in the tissue compartment. (a) Overlay histograms showing mean fluorescent intensity (MFI) for CD38, CD69, and CXCR4 (CD184) on xenografted CLL cells from the mouse spleen (SP) and PB. (b) NSG mice (n=13) injected with PBMCs from six different patients were sacrificed 3–4 weeks post xenografting. Each dot represents a sample from one mouse; lines connect PB and SP samples from the same mouse. (c) CLL cells in the mouse spleen (SP) and human lymph node (LN) upregulate activation markers and downregulate CXCR4 compared to circulating cells in the PB. Shown is the mean (± SEM) of the relative expression for the indicated cell surface markers calculated as the MFI ratio of xenografted CLL cells in mouse SP to mouse PB (open bars) and of CLL cells in human LN to human PB (black bars) obtained from 3 patients. Student's t-test was used to test for significance in all panels.
Mentions: In keeping with observations in patients, we found that xenografted CLL cells in the murine spleen as compared to matched PB samples showed significantly increased expression of the activation markers CD38 and CD69 (Figure 2a-b, P = .03 and P < .001, respectively). Similarly, CLL cells in the murine spleen expressed less CXCR4 than circulating CLL cells (Figure 2a-b, P < .001), likely as a result of binding to its ligand CXCL12/SDF-1.

Bottom Line: We found that the murine spleen (SP) microenvironment supported CLL cell proliferation and activation to a similar degree than the human LN, including induction of BCR and NF-κB signaling in the xenografted cells.Next, we used this model to study ibrutinib, a Bruton's tyrosine kinase inhibitor in clinical development.Ibrutinib inhibited BCR and NF-κB signaling induced by the microenvironment, decreased proliferation, induced apoptosis and reduced the tumor burden in vivo.

View Article: PubMed Central - PubMed

Affiliation: Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA.

ABSTRACT
Chronic lymphocytic leukemia (CLL) cells depend on microenvironmental factors for proliferation and survival. In particular, the B-cell receptor (BCR) and nuclear factor- κB (NF-κB) pathways are activated in the lymph node (LN) microenvironment. Thus, model systems mimicking tumor-host interactions are important tools to study CLL biology and pathogenesis. We investigated whether the recently established NOD/scid/γc() (NSG) mouse xenograft model can recapitulate the effects of the human microenvironment. We assessed, therefore, tumor characteristics previously defined in LN-resident CLL cells, including proliferation, and activation of the BCR and NF-κB pathways. We found that the murine spleen (SP) microenvironment supported CLL cell proliferation and activation to a similar degree than the human LN, including induction of BCR and NF-κB signaling in the xenografted cells. Next, we used this model to study ibrutinib, a Bruton's tyrosine kinase inhibitor in clinical development. Ibrutinib inhibited BCR and NF-κB signaling induced by the microenvironment, decreased proliferation, induced apoptosis and reduced the tumor burden in vivo. Thus, our data demonstrate that the SP of xenografted NSG mice can, in part, recapitulate the role of the human LN for CLL cells. In addition, we show that ibrutinib effectively disrupts tumor-host interactions essential for CLL cell proliferation and survival in vivo.

Show MeSH
Related in: MedlinePlus