CD44 expression in T-cell lymphoblastic leukemia.

1. CD44 is an adhesion molecule expressed by B and T lymphocytes that mediates cell attachment to extracellular matrix components and specific cell surface ligands. In normal process of T-cell development, CD44 can be implicated in homing of bone marrow-derived T-cell precursors into the thymus. In hematopoietic malignancies, CD44 and other adhesion molecules can mediate the behavior of neoplastic cells such as metastatic migration. In the leukemic process, CD44 expression is correlated with increased numbers of circulating blasts and it is present at other sites such as the central nervous system. 2. In the present study, CD44 was investigated in lymphoblasts from 30 patients with T-cell lymphoblastic leukemia (T-ALL) and in peripheral lymphocytes from 10 healthy individuals. CD44 expression was detected in 23 (77%) of T-ALL cases studied and was correlated with clinical features such as mediastinal mass, adenomegaly, and infiltration of the central nervous system and other organs. Interestingly, CD44 expression in patients with tumor infiltration was higher than in patients with no tumor infiltration. 3. These data suggest that CD44 may be regarded as an additional marker for tumor expansion in T-cell leukemias.