ZAP-70 Promotes the Infiltration of Malignant B-Lymphocytes into the Bone Marrow by Enhancing Signaling and Migration after CXCR4 Stimulation

Abstract

ZAP-70 in chronic lymphocytic leukemia (CLL) is associated with enhanced response to microenvironmental stimuli. We analyzed the functional consequences of ZAP-70 ectopic expression in malignant B-cells in a xenograft mouse model of disseminated B-cell leukemia. Mice injected with B-cells expressing ZAP-70 showed a prominently higher infiltration of the bone marrow. In vitro analysis of the response of malignant B-cells to CXCL12, the main attracting chemokine regulating trafficking of lymphocytes to the bone marrow, or to bone marrow stromal cells, revealed that ZAP-70 induces an increased response in terms of signaling and migration. These effects are probably mediated by direct participation of ZAP-70 in CXCL12-CXCR4 signaling since CXCR4 stimulation led to activation of ZAP-70 and downstream signaling pathways, such as MAPK and Akt, whereas ZAP-70 did not alter the expression of the CXCR4 receptor. In addition, subclones of primary CLL cells with high expression of ZAP-70 also showed increased migrative capacity toward CXCL12. Neutralization of CXCR4 with a monoclonal antibody resulted in impaired in vitro responses to CXCL12 and bone marrow stromal cells. We conclude that ZAP-70 enhances the migration of malignant B-cells into the supportive microenvironment found in the bone marrow mainly by enhancing signaling and migration after CXCR4 stimulation.

The role of ZAP70 kinase in acute lymphoblastic leukemia infiltration into the central nervous system

“…This observation differs from the situation in B-CLL, where cells with lower ZAP70 expression showed a reduced BM homing. 21,22 In JURKAT T-ALL cells, downregulation of ZAP70 did not prevent CNS infiltration; however, it was associated with a reduction in CNS blasts recovered from xenografts ( Figure 1D). Downregulating ZAP70 in JURKAT cells did not prolong xenograft survival.…”

“…ZAP70 has been shown to enhance the migration of malignant B cells to the bone marrow (BM) by upregulating adhesion molecules and chemokine receptors (CCRs), 21,22 and is also required for C-X-C motif chemokine ligand 12 (CXCL12)-mediated T-cell transendothelial migration. 23,24 In T-cell acute lymphoblastic leukemia (T-ALL), the chemokine receptors CCR7 and CXCR4 have been associated with an increased capability of T-ALL cells to enter the CNS, mainly in cell line models.…”

Induction of Regulatory B-Cells by Mesenchymal Stem Cells is Affected by SDF-1α-CXCR7

“…Optical density (OD) was measured at 490 nm. Cell viability was evaluated after 48 h of culture with FCM using Annexin V-APC-Propidium Iodide (PI) staining, as described previously [32]. Cytotoxicity was additionally determined by measuring the amunt of dehydrogenase (LDH) released in cell culture medium using an LDH assay kit (Sigma) via recording absorption at 340 nm according to the protocolof the manufacturer.…”

Differential expression and function of CD27 in chronic lymphocytic leukemia cells expressing ZAP-70

“…CLL is a heterogeneous disease, with several prognostic biomarkers available including expression of zeta-chain TCR-associated protein kinase 70 kDa (ZAP-70) which is correlated with more rapid disease progression [8,9]. Besides serving as a clinical biomarker, ZAP-70 expression in CLL has been proposed to affect signaling pathways including those triggered by B cell antigen receptor [10,11], leading to altered expression and function of molecules involved in tissue homing [12,13]. While CLL interactions with lymphoid tissue microenvironments are critical for CLL survival and disease progression, the underlying mechanisms and relation to disease heterogeneity are not completely understood.…”