CCL3 as Possible Negative Prognostic Factor in Chronic Lymphocytic Leukemia

Both microenvironmental signals from surrounding cells and changes in the genome of leukemic cells play essential role in the development of chronic lymphocytic leukemia. Nurse-like cells (NLCs) are one of the important elements of the microenvironment of CLL cells. The key role in the interactions of leukemic cells with NLCs is played by chemokines, which may interfere with the programmed cell death process in the leukemic lymphocytes. The aim of our study was analysis of selected microenvironmental factors having a potential impact on the leukemic cells survival, as well as their association with clinical, cytogenetic, and molecular parameters. For this study, we selected three types of molecules which can modulate microenvironment: chemokines IL-8 and CCL3 (which are classically secreted to extracellular matrix), soluble forms of adhesion molecules JAG1 and CD163, and secreted form of endogenous protein BIRC5. We assessed their expression in the serum of CLL patients as well as in medium of long-term NLCs cultures.

Long-term cell culture was prepared from mononuclear cells derived from the blood of 34 patients with CLL. Number of NLCs cells was evaluated, under a light inverted microscope. The concentration of IL-8, CCL3, sBIRC5, sCD163, and sJAG1 in culture medium and serum was assessed by enzyme-linked immunosorbent assays.

There were significant differences in the concentration of IL-8, sBIRC5, CCL3, sCD163, and sJAG1 between the patient's blood serum and the culture medium. The concentrations of IL-8, CCL3, and JAG1 were higher in the culture medium, which confirmed the role of the microenvironment in the production of these proteins. In addition, the concentration of CCL3 chemokine in both patient's blood serum and in the culture medium correlated with the number of NLCs and with known prognostic factors in the course of CLL, e.g., Rai stage, WBC, expression of ZAP-70, CD38, and CD5/19.

The microenvironment of CLL cells, which includes NLCs, plays an important role in the pathogenesis of CLL. The CCL3 chemokine seems to be a good factor representing microenvironment of CLL cells. Chronic lymphocytic leukemia is a complex and very heterogeneous disease; therefore, its progress should be considered both in the context of genetic changes and the interaction with microenvironmental cells.