The transferrin receptor: its diagnostic value and its potential as therapeutic target.

Transferrin receptors are present on almost all mammalian cells. The receptor participates in the cellular acquisition of iron from transferrin by receptor-mediated endocytosis. Receptor abundancy is generally regulated by two factors: i) cellular iron status and ii) cell growth. These two factors form the basis for the utilization of transferrin receptor determination as a diagnostic tool. In the assessment of body iron status and erythropoietic activity the measurement of circulating transferrin receptor has proved to be of value as a measure of mild tissue iron deficiency, to distinguish iron deficiency anemia from the anemias of chronic disease, and as a sensitive index of iron deficiency during pregnancy. Histochemical analysis of the presence and abundancy of the transferrin receptor will continue to serve as an additional tool in special cases to distinguish between malignant and normal cell growth, and to provide additional information about the biological behaviour of tumor cells. Finally, the transferrin receptor holds a potential as a target for direct and indirect drug delivery in the therapy of malignant cell growth.