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

A transferrin receptor was demonstrated in tumor tissue from 10 patients with breast carcinoma and one 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, whereas 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 = 9.0 × 108M. The binding site is specific for transferrin, as studies show that non‐radioactive transferrin displaced labelled 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 Mr 90,000 daltons, which is of similar molecular weight found for the putative transferrin receptor in all of a series of human cultured cell lines previously examined.