Demonstration of the transferrin receptor in human breast cancer tissue. Potential marker for identifying dividing cells

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Abstract
A transferrin receptor was demonstrated in tumor tissue from 10 patients with breast carcinoma and 1 patient with breast sarcoma. Binding studies were conducted by measuring the amount of 125I-transferrin binding to microsomal preparations of the tumor tissue. Elevated levels of specific transferrin binding were found in the tumors with a range of 11-35% of bound transferrin; microsomes prepared from non-neoplastic breast tissue samples bound only 2.3 and 2.4% of the transferrin. Scatchard analysis of binding studies conducted with tissues from a breast cancer and from a breast sarcoma indicate that the receptor has a Ka [association constant] = 9.0 .times. 108 M. The binding site is specific for transferrin, as studies show that non-radioactive transferrin displaced labeled transferrin, while human IgG and human albumin did not. The receptor-transferrin complex was precipitated from a detergent extract of the breast sarcoma with antiserum to human transferrin. Sodium dodecyl sulfate/polyacrylamide gel electrophoresis of the immunoprecipitate gave a polypeptide of MW 90,000 daltons, which is of similar MW to that found for the putative transferrin receptor in all of a series of human cultured cell lines previously examined.