Phenotype and immune function of lymph node and peripheral blood CLL cells are linked to transendothelial migration

everal lines of evidence suggest that homing of tumor cells to lymphoid tissue contributes to disease progression in chronic lymphocytic leukemia (CLL). Here, we demonstrate that lymph node (LN)-derived CLL cells possess a distinct phenotype, and exhibit enhanced capacity for T-cell activation and superior immune synapse formation when compared with paired peripheral blood (PB) samples. LN-derived CLL cells manifest a proliferative, CXCR4(dim)CD5(bright) phenotype compared with those in the PB and higher expression of T-cell activation molecules including CD80, CD86, and HLA-D-related (DR). In addition, LN-CLL cells have higher expression of α4β1 (CD49d) which, as well as being a co-stimulatory molecule, is required for CLL cells to undergo transendothelial migration (TEM) and enter the proliferation centers of the LNs. Using an in vitro system that models circulation and TEM, we showed that the small population of CLL cells that migrate are CXCR4(dim)CD5(bright) with higher CD49d, CD80, CD86, and HLA-DR compared with those that remain circulating; a phenotype strikingly similar to LN-derived CLL cells. Furthermore, sorted CD49d(hi) CLL cells showed an enhanced capacity to activate T cells compared with CD49d(lo) subpopulations from the same patient. Thus, although PB-CLL cells have a reduced capacity to form immune synapses and activate CD4(+) T cells, this was not the case for LN-CLL cells or those with the propensity to undergo TEM. Taken together, our study suggests that CLL cell immunologic function is not only modulated by microenvironmental interactions but is also a feature of a subpopulation of PB-CLL cells that are primed for lymphoid tissue homing and interaction with T cells

Evidence for a macromolecular complex in poor prognosis CLL that contains CD38, CD49d, CD44 and MMP-9

International audienceProgressive chronic lymphocytic leukaemia is characterised by the accumulation of neoplastic B-cells in the tissues and correlates with the expression of prognostic biomarkers such as CD38, CD49d and matrix metalloproteinase-9 (MMP9), which are involved in migration and tissue invasion. In this study we investigated the physical relationship between these molecules and demonstrate that CD38, CD49d, MMP9 and CD44 are physically associated in a supramolecular cell surface complex. Our findings provide a molecular basis for the correlation between expression of these proteins and prognosis and, since the complex is not present in normal B-cells, suggest a novel leukaemia-specific therapeutic target

Mimicking the tumour microenvironment: three different co-culture systems induce a similar phenotype but distinct proliferative signals in primary chronic lymphocytic leukaemia cells

Interactions in the tumour microenvironment can promote chronic lymphocytic leukaemia (CLL) cell survival, proliferation and drug resistance. A detailed comparison of three co-culture systems designed to mimic the CLL lymph node and vascular microenvironments were performed; two were mouse fibroblast cell lines transfected with human CD40LG or CD31 and the third was a human microvascular endothelial cell line, HMEC-1. All three co-culture systems markedly enhanced CLL cell survival and induced a consistent change in CLL cell phenotype, characterized by increased expression of CD38, CD69, CD44 and ITGA4 (CD49d); this phenotype was absent following co-culture on untransfected mouse fibroblasts. In contrast to HMEC-1 cells, the CD40LG and CD31-expressing fibroblasts also induced ZAP70 expression and marked CLL cell proliferation as evidenced by carboxyfluorescein succinimidyl ester labelling and increased Ki- 67 expression. Taken together, our data show that co-culture on different stroma induced a remarkably similar activation phenotype in CLL cells but only the CD40LG and CD31-expressing fibroblasts increased ZAP70 expression and CLL cell proliferation, indicating that ZAP70 may play a critical role in this process. This comparative study reveals a number of striking similarities between the co-culture systems tested but also highlights important differences that should be considered when selecting which system to use for in-vitro investigations

CD38 expression in chronic lymphocytic leukemia is regulated by the tumor microenvironment

Chronic lymphocytic leukemia (CLL) is a lymphoproliferative disease with a highly variable outcome. The prognosis of patients with CLL may be predicted using a number of biomarkers, including the level of CD38 expression at the leukemic cell surface. This study investigates the hypothesis that CD38 expression by CLL cells reflects interactions with nonmalignant cells within pseudofollicles in secondary lymphoid tissue where tumor cell proliferation is thought to occur. CD38 expression is higher in tissues that contain pseudofollicles compared with those that do not. In addition, we show that CD38 expression in CLL is dynamic, changes in response to contact with activated CD4(+) T cells, and identifies cells that are primed to proliferate. Finally, we demonstrate close contact between activated CD4+ T cells and proliferating tumor in primary patient tissue. Proliferating tumor cells in lymph nodes express CD38, which is in turn associated with an increased number of CD31(+) vascular endothelial cells. Although the factors resulting in colocalization of tumor, T cells, and endothelium remain unclear, the existence of these cellular clusters may provide an explanation for the association between CD38 expression and adverse outcome in CLL and suggests novel therapeutic targets