Alterations Of The Chemokine Microenvironment In Chronic Lymphocytic Leukemia

In chronic lymphocytic leukemia (CLL), proliferation of the leukemic cell clone occurs in the bone marrow and lymphatic tissues rather than peripheral blood. In this microenvironment, CLL cells interact with accessory cells, such as T-cells and CD68+ nurselike cells (NLCs). In addition, cytokines and chemokines secreted by leukemic cells, stromal cells and T-cells are essential in forming the disease-specific microenvironment. However, the exact biological role of cytokines and chemokines needs to be defined.

In order to address this issue, we measured serum levels of 20 chemokines and cytokines in a prospective cohort of 159 previously untreated Binet stage A patients (pts) (GCLLSG CLL1 trial), 50 pts with advanced CLL in need of first line treatment (GCLLSG CLL8 trial) and 27 healthy individuals. For the study cohorts, serum samples had been centrally collected at study entry and stored at -80°C. Sera were analyzed on a Luminex-based multiplex platform, allowing simultaneous screening of multiple serum parameters.

Serum levels of 13 chemokines (EGF, MCP-1, MIP-1alpha, MIP-1beta, sIl2Ralpha, VEGF, MCP-2, MCP-4, SDF-1, 6CKine, CTACK, TRAIL, SCF) differed significantly between healthy controls and CLL patients (p<0.05), indicating that the expression of these cytokines may potentially impact pathways common to CLL and the disease specific microenvironment. In addition, 7 chemokine serum levels were significantly higher in advanced stage CLL compared to patients at primary diagnosis, indicating a pronounced shift of the chemokine homeostasis upon disease progression. (Table)

We identified a strong correlation of inflammatory cytokines (TRAIL, TNFalpha; p=0.039), growth factors (EGF, VEGF, TPO, SCF; p<0.001) and chemokines involved in B- and T-cell migration and homing (MIP-1alpha, MIP-1beta, 6CKine, Il-16; p<0.05). These coordinately regulated cytokines may reflect pathways important to the pathobiology of CLL. Hierarchical cluster analyses revealed distinct chemokine expression patterns in healthy individuals, early CLL and advanced stage disease. Finally, sIl2Ralpha has been previously confirmed as an independent prognostic factor in early stage CLL

Due to the comparison of 27 healthy individuals and 209 CLL pts we were able to demonstrate that the chemokine homeostasis is significantly altered in CLL compared to healthy individuals. Chemokines involved in B- and T-cell migration and homing and recruitment, inflammation and growth factors are coordinately overexpressed, pointing towards pathways crucial to the formation of a disease specific microenvironment. These pathways might serve as potential targets for future therapeutic strategies.

No relevant conflicts of interest to declare.