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High levels of the shed form of L-selectin are present in patients with acute leukemia and inhibit blast cell adhesion to activated endothelium
Comparative Study Journal Article Research Support, Non-U.S. Gov't --- Old month value: Aug 15
L-selectin is expressed by most leukocytes and mediates the initial step of adhesion to vascular endothelium. A feature of this adhesion receptor is to be shed from the cell surface. We report here the presence of high levels of the shed form of L-selectin (sL-selectin) in plasma from patients with acute leukemia. We also show that sL-selectin purified from acute leukemia plasma exhibits functional activity. The mean (+/- 1 SD) plasma level of sL-selectin among 100 healthy individuals was 2.1 +/- 0.7 micrograms/mL. This value was increased (> 2 SD above the mean) in 63% of 58 patients with acute lymphoblastic leukemia (ALL) and 59% of 93 patients with acute myelogenous leukemia ([AML] P < .001). Repeated measurements in 24 patients showed normal-range levels in 16 of 16 patients in complete remission and high levels in eight of eight patients with therapy-resistant acute leukemia or leukemia relapse. Furthermore, elevated sL-selectin levels were detected in cerebrospinal fluid of three patients with ALL suffering from a relapse limited to the central nervous system. Epitope mapping with monoclonal antibodies demonstrated that L-selectin shedding from leukemic blasts was accompanied by conformational changes of its epidermal growth factor-like domain. A functional role for sL-selectin purified from leukemic plasma was supported by its ability to completely inhibit L-selectin-dependent adhesion of blast cells to tumor necrosis factor-alpha (TNF-alpha)-activated endothelium in vitro. These results suggest that sL-selectin may have an important role in the regulation of leukemic cell adhesion to endothelium. In addition, monitoring of the sL-selectin level may be useful for evaluating leukemia activity, in particular for the detection of leukemia relapse.
Antigens, CD/blood Antineoplastic Combined Chemotherapy Protocols/therapeutic use Blast Crisis/*immunology Blotting, Western *Cell Adhesion Cell Adhesion Molecules/*blood Cells, Cultured Endothelium, Vascular/*physiology Enzyme-Linked Immunosorbent Assay Humans Immunophenotyping L-Selectin Leukemia, Lymphocytic, Acute/*blood/drug therapy/immunology/pathology Leukemia, Myelocytic, Acute/*blood/drug therapy/immunology/pathology Lymphocytes/immunology Predictive Value of Tests Prognosis Reference Values Tumor Markers, Biological/*blood Umbilical Veins
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