Shedding of CD9 Antigen in Acute Lymphoblastic Leukemia

Abstract

A leukemia-associated CD9 glycoprotein antigen released into the extracellular milieu from acute lymphoblastic leukemia cells has been detected using a unique lectin-monoclonal antibody immunoassay. It has been demonstrated that the release of CD9 antigen is an active process and is associated with active cell growth. In addition, the difference of carbohydrate moiety, and hence glycosylation, in the CD9 antigen derived from lymphoblasts and neuroblasts was verified using lectin affinity chromatography. The lectin affinity of the carbohydrate moiety of lymphoblast CD9 antigen would indicate the presence of N-linked oligosaccharide chains having groups of N-acetyl glucosamine residues, a mannose core and a terminal D-galactose. The soluble CD9 antigen is specifically detected in plasma from ALL patients at the time of diagnosis, in cerebrospinal fluid from patients with central nervous system involvement, and spent medium from CD9-positive leukemic blasts obtained at the time of diagnosis. Interestingly when bone marrow cells taken from patients in complete remission were studied, a distinct amount of CD9 antigen was released into spent medium in some of the cases. All of these patients have subsequently developed hematological relapse. The present data suggest that shedding of CD9 antigen by leukemic cells may enable the clinical monitoring of residual leukemic cell burden.

Mutation of juxtamembrane cysteines in the tetraspanin CD81 affects palmitoylation and alters interaction with other proteins at the cell surface

“…Most tetraspanin-specific antibodies would not detect these bands, since they bind at the large extracellular loop. There have been previous reports of shedding of soluble CD9-immunoreactive material into extracellular fluid by certain types of tumor cells [33]. It is not clear whether the CD81 processing that we have observed and this previously reported shedding of CD9 involve similar proteases or cleavage events.…”

Detection and Quantification of Soluble Intercellular Adhesion Molecule‐1 (slCAM‐1) in the Serum and Urine of Patients with Bladder Cancer

“…The patients were divided into groups of either superficial (Tis to T1) or invasive (T2 to T4) cancer. The mean age of the patients was 66.8 years (range, 30 mented by imaging and histologic examination. The pathologic staging and grading of bladder carcinoma were performed according to the Japanese general rules for clinical and pathological studies on bladder cancer.'?…”

Immunophenotypic patterns and cytogenetic anomalies in acute non-lymphoblastic leukemia subtypes: a prospective study of 432 patients

“…8,21,22 shown that CD9 is released by CD9-positive ALL blast and may be related to poor prognosis. 26 Interestingly, the combiAt least one cytogenetic abnormality was identified in 54% of cases.…”