Investigation of L-selectin and ADAM17 in chronic lymphocytic leukemia

Introduction: L-selectin (CD62L), a cell adhesion molecule and homing receptor of lymphocytes, was found to be elevated in soluble form in plasma of patients with chronic lymphocytic leukemia (CLL). It was suggested that L-selectin expression also correlates with the disease progression. ADAM17/TACE (tumor necrosis factor α converting enzyme), a metalloproteinase, was previously shown to play a dominant role in the shedding of L-selectin. In this study we want to observe the surface expression of ADAM17 in relation to L-selectin expression in different leukocytes of CLL patients
Methods: We studied peripheral blood samples anticoagulated with K3EDTA obtained from healthy individuals (n=19) and untreated CLL patients (n=19). Red blood cells were lysed and immunostaining was carried out with monoclonal antibodies: anti-hTACE-FITC (CD156b-FITC), CD62L-PE, CD5-PerCPCy5.5, CD19-PECy7, IgG2a-FITC. The four-color staining was analyzed by flow cytometry using a Beckman Coulter Cytomics FC500. Fluorescent values of CD62L were expressed by Mean Fluorescent Intensity (MFI); CD156b and its isotype control fluorescent values were calculated in Relative Fluorescent Intensity (RFI).
Results: There was a markedly decreased surface expression of ADAM17 and CD62L on B-cells of CLL patients compared to controls: ADAM17/ IgG2a RFI: 7.2 ± 1.73 vs. 3.7±1.4; (p<0.05), CD62L MFI: 50 ± 4.5 vs. 26 ± 5.6; (p<0.05). Although, L-selectin expression was significantly lower also on the T-cells of CLL patients (p<0.05) their ADAM17 expression was similar to controls. Neutrophil and monocyte L-selectin and ADAM17 staining was not different in patients and controls.
Discussion: Our results show that there is an alteration of ADAM17 and L-selectin surface expression on the B-cells in CLL. This decrease of ADAM17 suggests a possible shedding of the molecule to the plasma, which may be related to the course or the severity of the disease.