Interaction between Transferrin and Tumor Cell Receptor

Abstract

A transferrin receptor was demonstrated in eight human established cell lines. Binding studies were conducted by measuring the amount of 125 I-labeled diferric transferrin binding to these cultured cells indicated that the number of transferrin receptor per cell was distributed between 0.37 ± 0.22 × 10 5 and 4.96 ± 0.61 × 10 5 , and association constant was between 1.91± 0.48 × 10 8 and 2.58 0.81 × 10 8 M -1 by scatchard analysis. The binding site was specific for diferric transferrin, as studies showed that non-radioactive transferrin displaced labeled transferrin, while human albumin and IgG did not. In addition, only diferric transferrin could bind the transferrin receptors. However apotransferrin and two forms of monoferric transferrin did not show any significant binding to K-562 cells using 125 I- labeled transferrins with different iron saturation. Moreover, number of transferrin receptor was markedly increased after s phase synclonization with thymidine and hydroxyurea. These experimental results clarified the specificity of transferrin receptors and suggested the possibility of transferrin receptors as a marker for cell proliferation.