CXCL12-induced VLA-4 activation is impaired in trisomy 12 chronic lymphocytic leukemia cells: a role for CCL21

Abstract

Homing to distinct lymphoid organs enables chronic lymphocytic leukemia (CLL) cells to receive pro-survival and proliferative signals. Cytogenetic aberrations can significantly affect CLL cell compartmentalization. Trisomy 12 (tri12) defines a CLL subgroup with specific clinical features and increased levels of the negative prognostic marker CD49d, the α4-subunit of the integrin VLA-4, which is a key regulator of CLL cell homing to bone marrow (BM). Chemokine-induced inside-out VLA-4 activation, particularly via the CXCL12-CXCR4 axis, increases the arrest of various cell types on VCAM-1 presenting endothelium. Here, we demonstrate that high CD49d expression in tri12 CLL is accompanied by decreased CXCR4 expression. Dissecting functional consequences of these alterations, we observed that tri12 CLL cell homing to murine BM is not affected by CXCR4-CXCL12 blockage using AMD3100 or olaptesed pegol/NOX-A12. In line, CCL21-CCR7 rather than CXCL12-CXCR4 interactions triggered VLA-4-mediated arrests of tri12 CLL cells to VCAM-1 under blood flow conditions. Concordantly, in real-time kinetic analyses we found CCL21 but not CXCL12 being capable to induce inside-out VLA-4 conformational changes in this CLL subgroup. Our results provide novel insights into the peculiar clinico-biological behaviour of tri12 CLL and emphasize its specific chemokine and integrin utilization during pathophysiologically and therapeutically relevant interactions with the microenvironment.

ZAP70 expression enhances chemokine‐driven chronic lymphocytic leukemia cell migration and arrest by valency regulation of integrins

“…Both OSU-CLL cell lines expressed high levels of CCR7 and low levels of CXCR4 ( Fig. 1B), which is in line with chemokine receptor expression profiles found in trisomy 12-positive CLL cells (14). Control experiments revealed that primary human PBLs and mature monocyte-derived dendritic cells express similar mRNA levels of CCR7 but lower levels of CXCR4 compared with the OSU-CLL cell lines (Supplemental Fig.…”

“…Trisomy 12-positive CLL cells display higher rates of cell proliferation (13) and lymph node involvement (14,15), and consequently patients carrying trisomy 12 CLL cells are susceptible to a fast disease progression (16). Moreover, trisomy 12 CLL cells are described to express high levels of the integrins very late antigen ABBREVIATIONS: BCR, B-cell receptor; BSA, bovine serum albumin; CD, cluster of differentiation; CLL, chronic lymphocytic leukemia; HEV, high endothelial venule; huICAM, human intercellular adhesion molecule; huVCAM, human vascular cell adhesion molecule; ICAM, intercellular adhesion molecule; IgV H , immunoglobulin heavy chain variable region; LFA-1, lymphocyte function-associated antigen; OSU, Ohio State University; PBL, peripheral blood lymphocyte; pMBMEC, primary mouse brain microvascular endothelial cell; VCAM, vascular cell adhesion molecule; VLA, very late antigen; ZAP70, z-associated protein of 70 kDa (VLA)-4 and lymphocyte function-associated antigen (LFA)-1, which facilitate integrin-mediated cell adhesion and motility (11,12,14,17). Cluster of differentiation (CD)49d, the a-chain of VLA-4, is considered a negative prognostic marker in CLL (18), particularly for trisomy 12-positive CLL (11).…”

“…Increased expression of CCR7 and CXCR4 correlates with lymphadenopathy in CLL (24)(25)(26). Trisomy 12-positive CLL cells expressing high levels of CD49d down-modulate CXCR4 and hence exploit CCR7 over CXCR4 to trigger activation of VLA-4 (14).…”

Combined CXCR3/CXCR4 measurements are of high prognostic value in chronic lymphocytic leukemia due to negative co-operativity of the receptors

“…7 We investigated whether CXCR3 and CXCR4 functionally influence each other in CLL. Performing chemotaxis assays as previously described, 8 we found that CLL cells pre-stimulated with either CXCR3 ligand CXCL9, CXCL10, or CXCL11 exhibited significantly reduced directed cell migration towards CXCL12 ( Figure 2Ai). Pre-stimulation with a small-molecule high-affinity CXCR3 agonist (VUF11418) 9 confirmed this observation and an antagonist (VUF11211) 9 did not interfere with chemotactic ability (Figure 2Aii).…”

“…(B) Shear flow assays were performed as previously described. 8 CLL cells were pretreated with (i) CXCL11 or (ii) the CXCR3 agonist and antagonist where indicated and perfused for 1 min at 0.5 dyn/cm 2 over VCAM-1 co-immobilized with CXCL12. Categories of interactions (tethers) are expressed as frequencies of cells in direct contact with the substrate.…”