Difference in the relative distribution of CD4+ T-cell subsets in B-CLL with mutated and unmutated immunoglobulin (Ig) VH genes: implication for the course of disease.

B-cell chronic lymphocytic leukemia (B-CLL) is a clinically heterogeneous disease in which the clinical course is influenced by the presence or absence of immunoglobulin (Ig) variable heavy chain (VH) gene mutations. The poor clinical outcome of the subgroup with unmutated Ig VH genes has been linked to the persistent ability of the B-cell receptor in tumor cells from these cases to respond to antigen. As B-cell receptor signaling generally relies on T-cell help, we hypothesized that the course of B-CLL might not only be influenced by the Ig VH mutational status but also by the activation/differentiation status of T cells. We assessed the relative distribution of naive and memory T-cell subsets in peripheral blood from patients with mutated (M-CLL, n=71) and unmutated Ig VH genes (UM-CLL, n=42) and correlated it with the course of disease. We also compared the prosurvival potential of naive and memory T cells cocultured with B-CLL cells in vitro. A significant increase in relative numbers of central and effector memory T cells was observed in the CD4 T-cell pool from UM-CLL as compared with M-CLL cases and was associated with high Rai stage, progressive disease and shorter treatment-free survival (TFS). In a multivariate analysis, the relative number of CD4 central and effector memory T cells remained a significant prognostic parameter for TFS after correction for CD38 expression, Ig VH status, genomic aberrations, and Rai stage. The inverse correlation of memory CD4 T cells with TFS might be explained by their potential to support survival of B-CLL cells.

Circulating B-cell chronic lymphocytic leukemia cells display impaired migration to lymph nodes and bone marrow.

Homing to secondary lymphoid organs and bone marrow (BM) is a central aspect of leukemic pathophysiology. We investigated the roles of the two major lymphocyte integrins LFA-1 and VLA-4 on B-cell chronic lymphocytic leukemia (CLL) cells in these processes. We found that the majority of CLL cells expressed significantly reduced LFA-1 due to low beta2 integrin transcripts. VLA-4 expression was heterogeneous but underwent rapid activation by the BM chemokine CXCL12. CLL cells failed to transmigrate across VCAM-1-expressing, ICAM-1-expressing, and CXCL12-expressing endothelium, whereas when LFA-1 expression was regained in subsets of CLL cells, these lymphocytes rapidly transmigrated the endothelium. Furthermore, when injected into tail veins of immunodeficient mice, normal B cells rapidly homed to lymph nodes (LN) in a LFA-1-dependent manner, whereas CLL cells did not. Nevertheless, only residual CLL subsets could reenter BM, whereas both normal and CLL cells homed to the mice spleen in an LFA-1-independent and VLA-4-independent manner. Our results suggest that CLL cells have a reduced capacity to adhere and transmigrate through multiple vascular endothelial beds and poorly home to lymphoid organs other than spleen. Integrin blocking could thus be an efficient strategy to prevent circulating CLL cells from reaching prosurvival niches in LNs and BM but not in spleen.

Expression levels of CD38 in T cells predict course of disease in male patients with B-chronic lymphocytic leukemia.

CD38 expression of tumor cells has been identified as an important prognostic factor in B-cell chronic lymphocytic leukemia (B-CLL). Although CD38 is involved in effector functions of T cells, the prognostic value of CD38+ T cells has not yet been addressed in B-CLL. In the present study, CD38-expression levels in B-CLL cells and T cells from 204 patients were analyzed by flow cytometry and correlated with clinical and molecular risk parameters. CD38 expression significantly differed in the neoplastic clone from patients with low versus advanced stage, irrespective of the sex of patients. In contrast, CD38 expression was generally higher in T cells from female compared with male patients but only increased in male patients in a stage-dependent manner. In male patients, combined analysis of CD38 in T cells and B-CLL cells identified 4 subgroups with significantly different treatment-free survival. Multivariate analysis including Rai stage and molecular risk parameters of the neoplastic clone identified CD38-expression levels in T cells as an independent prognostic factor in male patients. Combined analysis of CD38 in B-CLL and T cells is superior in predicting outcome of male B-CLL patients than either parameter alone. Further studies are needed to elucidate the underlying mechanisms of the sex-specific role of CD38+ T cells in B-CLL.