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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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Ibrutinib reduces tumor burden and CLL cell viability in the NSG mice. NSG mice (n=40) injected with PBMCs from six patients were treated with vehicle (control) or ibrutinib and sacrificed 3-4 weeks later. (a) The absolute human CLL cell count in the PB of ibrutinib treated mice is higher than in control mice. Data points represent the average measurements of 2-5 mice injected with PBMC from the same patient, identified by unique symbols (Table 1). (b) CLL cell infiltration in the murine spleen is reduced by ibrutinib. Each data point represents one mouse; symbols identify individual patients (Table 1). (c) A representative histogram demonstrates decreased viability (measured by VIVID Live/Dead stain) in CLL cells in the spleen of an ibrutinib treated mouse (right panel) compared to a control mouse (left panel). (d) Decreased viability of CLL cells in the spleen of ibrutinib treated mice. Each data point represents one mouse; symbols identify patients (Table 1).
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Figure 4: Ibrutinib reduces tumor burden and CLL cell viability in the NSG mice. NSG mice (n=40) injected with PBMCs from six patients were treated with vehicle (control) or ibrutinib and sacrificed 3-4 weeks later. (a) The absolute human CLL cell count in the PB of ibrutinib treated mice is higher than in control mice. Data points represent the average measurements of 2-5 mice injected with PBMC from the same patient, identified by unique symbols (Table 1). (b) CLL cell infiltration in the murine spleen is reduced by ibrutinib. Each data point represents one mouse; symbols identify individual patients (Table 1). (c) A representative histogram demonstrates decreased viability (measured by VIVID Live/Dead stain) in CLL cells in the spleen of an ibrutinib treated mouse (right panel) compared to a control mouse (left panel). (d) Decreased viability of CLL cells in the spleen of ibrutinib treated mice. Each data point represents one mouse; symbols identify patients (Table 1).

Mentions: While Bagnara et al showed that depletion of T-cells in the xenografted NSG mice inhibits CLL cell proliferation,39 the effect of the emerging BCR directed therapies have not been investigated in this model. We therefore treated NSG mice with the BTK inhibitor ibrutinib to determine its in vivo effects on xenografted CLL cells. In keeping with observations that many patients show a transient increase in the absolute lymphocyte count at the start of ibrutinib therapy,26, 28 the CLL cell count in the PB of treated mice was higher than in untreated mice (Figure 4a). Concurrent with this increase of CLL cells in the PB, there was a statistically significant decrease in tumor cells in the spleens of ibrutinib treated mice (average reduction 23%, Figure 4b; P = .01). No significant change in T-cell numbers was observed in any of the mice (data not shown). This was further demonstrated by IHC as shown in Supplementary Figure S5.


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)

Ibrutinib reduces tumor burden and CLL cell viability in the NSG mice. NSG mice (n=40) injected with PBMCs from six patients were treated with vehicle (control) or ibrutinib and sacrificed 3-4 weeks later. (a) The absolute human CLL cell count in the PB of ibrutinib treated mice is higher than in control mice. Data points represent the average measurements of 2-5 mice injected with PBMC from the same patient, identified by unique symbols (Table 1). (b) CLL cell infiltration in the murine spleen is reduced by ibrutinib. Each data point represents one mouse; symbols identify individual patients (Table 1). (c) A representative histogram demonstrates decreased viability (measured by VIVID Live/Dead stain) in CLL cells in the spleen of an ibrutinib treated mouse (right panel) compared to a control mouse (left panel). (d) Decreased viability of CLL cells in the spleen of ibrutinib treated mice. Each data point represents one mouse; symbols identify patients (Table 1).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 4: Ibrutinib reduces tumor burden and CLL cell viability in the NSG mice. NSG mice (n=40) injected with PBMCs from six patients were treated with vehicle (control) or ibrutinib and sacrificed 3-4 weeks later. (a) The absolute human CLL cell count in the PB of ibrutinib treated mice is higher than in control mice. Data points represent the average measurements of 2-5 mice injected with PBMC from the same patient, identified by unique symbols (Table 1). (b) CLL cell infiltration in the murine spleen is reduced by ibrutinib. Each data point represents one mouse; symbols identify individual patients (Table 1). (c) A representative histogram demonstrates decreased viability (measured by VIVID Live/Dead stain) in CLL cells in the spleen of an ibrutinib treated mouse (right panel) compared to a control mouse (left panel). (d) Decreased viability of CLL cells in the spleen of ibrutinib treated mice. Each data point represents one mouse; symbols identify patients (Table 1).
Mentions: While Bagnara et al showed that depletion of T-cells in the xenografted NSG mice inhibits CLL cell proliferation,39 the effect of the emerging BCR directed therapies have not been investigated in this model. We therefore treated NSG mice with the BTK inhibitor ibrutinib to determine its in vivo effects on xenografted CLL cells. In keeping with observations that many patients show a transient increase in the absolute lymphocyte count at the start of ibrutinib therapy,26, 28 the CLL cell count in the PB of treated mice was higher than in untreated mice (Figure 4a). Concurrent with this increase of CLL cells in the PB, there was a statistically significant decrease in tumor cells in the spleens of ibrutinib treated mice (average reduction 23%, Figure 4b; P = .01). No significant change in T-cell numbers was observed in any of the mice (data not shown). This was further demonstrated by IHC as shown in Supplementary Figure S5.

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