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.

Improved risk assessment in B-cell chronic lymphocytic leukemia based on sex-specific molecular profiling

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Background: B-cell chronic lymphocytic leukemia (B-CLL) is a heterogeneous disease with some patients having an indolent course and others a rapidly progressing one. As underlying molecular mechanisms of differential disease activity, genomic aberrations, the mutational status of the variable region of the immunoglobulin heavy chain (Ig VH) and distinct expression levels of Zap-70 and CD38 have recently been identified, and their capacity to interact with survival and proliferation signals of B-CLL cells has directly been linked to progression and response to therapy. Although male sex has also been identified as risk factor for a more aggressive disease in B-CLL, the molecular basis for this interaction remains elusive. Methods: We compared the prognostic value of the above-mentioned molecular risk factors between female (n=88) and male patients with B-CLL (n=116). Differences in their frequency was evaluated using the Chi-square test. Their impact on treatment-free and overall survival of patients was analyzed using the Kaplan-Meier method and the log-rank test. The prognostic value of each molecular risk parameter in female and male patients was determined using the Cox proportional hazards regression model. Results: High CD38 expression (=30%), unmutated Ig VH gene (=98%) and unfavorable genetic aberrations (i.e. del17p, del11q or tri12) detected in the neoplastic clone identified patients with significantly shortened treatment-free survival, irrespective of the sex of patients. In contrast, Zap70 expression in more than 20% of B-CLL cells was negatively associated with treatment-free survival only in female (RR: 3.5, 95% CI 1.5 –7.9, P=.003) but not in male patients (RR: 1.6, 95% CI 0.9 –2.9, P=.089). In addition, we identified high CD38 expression in T-cells as independent negative prognostic marker in male (RR: 2.8, 95% CI 1.5 –5.0, P=.0006) but not in female patients (RR: 1.9, 95% CI 0.8 –4.6, P=.17). Based on these results we developed a novel sex-adapted algorithm for improved risk assessment in B-CLL. Conclusions: We identified sex-specific differences in the prognostic value of Zap-70 and CD38 in B-CLL. Whether this can be explained by modulation of their specific signaling pathways by sex hormones will have to be addressed in future studies.

No significant financial relationships to disclose.

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.