Evidence for Differential Regulation of Transferrin Receptor 1 in Normal vs. Malignant B Cells.

Transferrin receptor 1 (TfR1, CD71) expression is related to the proliferative state of the cells as well as the induction of differentiation; furthermore, CD71 is one of the “classical” activation markers up-regulated upon B-cell activation. As we have recently shown (Smilevska et al., Leuk Res 2005, in press), CLL is characterized by almost uniformly high CD71 expression, regardless of IGH mutational load; this is in keeping with the activated status of neoplastic cells. In the present study, we evaluated TfR1 expression at the mRNA and protein level in CD19+ B cells sorted from peripheral blood mononuclear cells of two healthy donors, 37 patients with typical chronic lymphocytic leukemia (CLL), as well as the BV173 (B cell acute lymphoblastic leukemia) and EHEB (human chronic B cell leukemia) cell lines. In all CLL cases, the tumor load was at least 70%. Twenty-two out of 37 CLL cases (59%) carried IGHV genes with