Correlation between the cellular expression of CD44 and the forms of acute lymphoblastic leukemia

Abstract

CD44 is an adhesion molecule expressed by B and T lymphocytes, that mediates cell attachment to extraceliular matrix componentes and adhesion to endothelial cells. The purpose of this study is to investigate the CD44 expression in 108 patients with lymphoblastic leukemia (57 B lineage ALL and 51 T-cell ALL) with a methodology that includes morphological analysis and immunophenotyping with a panel of monoclonal antibodies detected by standard techniques such as immunoperoxidase conjugated methods and flow-cytometry. lnitially we investigated the correlation of CD44 expression with all levels of cellular maturation of these leukemia, established according to antigen expression. Then, we investigated the correlation of this molecule with clinical-pathologic features such as mediastinal mass, adenomegaly and infiltration of the central nervous systein, and number of blastic cells in peripheral blood. In addition, we also investigated CD44 expression in peripheral lymphocytesfrom 11 healthy individuais. The CD44 expression was positive in 83 (76.8%) out of 108 ALL cases studied. In B precursors and B-ALL its expression was observed in 46 (80.8%) out of 57 cases and 37(72.5%) out of 51 cases of T-ALL. In the four subgroups of B precursor ALL, the expression of this molecule was found in 2 cases (66.7%) of null-ALL, in 34 cases (73.5%) of C-ALL and al cases of pre-B (cµ+) and B-ALL (Smlg+). Considering, T-cell ALL, the CD44 expression was variable among the three subgroups of this leukemia. In Subgroup 1 (pre-TALL) all 9 cases were positive (100%). In 14 Subgroups 11 (intermediate T-cell ALL) CD44 was positive in 4 cases (28.6%) and amongst the 28 cases of Subgroup III, CD44 was positive in 24 cases (85.7%). In lymphocytes from the control groups, CD44 expression was positive in all cases with percentages of reactivity ranging from 80% to 100% of cases, which homogeneously exhibited high density of CD44, as assessed by cytofluorimetrv. The correlation of CD44 expression in terms of clinical-pathologic profile o fALL demonstrated that high levels of CD44 were associated to tumoral forms of disease expressed as lymphadenopathy, hepatomegaly, splenomegaly, tumoral masses and infiltration of central nervous system. However, we did not find any association between CD44 and high leveis of circulating blast cells. These data suggest that CD44 should be considered au addicional marker to monitor evolution and asses the mechanisms of pathological evolution of the lvmphohlastic leukemia.