ABSTRACT
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 amont of 1251-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 x 10(8)M. 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 M 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.
Subject(s)
Breast Neoplasms/metabolism , Receptors, Cell Surface/isolation & purification , Transferrin/metabolism , Breast Neoplasms/pathology , Cell Division , Cell Membrane/metabolism , Female , Humans , Microsomes/metabolism , Protein Binding , Receptors, TransferrinABSTRACT
Serum and tumor tissue from breast cancer patients were evaluated for the presence of alpha subunit of hCG, by means of the specific radioimmunoassay. Elevated serum levels occurred in 0/50 (0%) of normal female controls, 1/17 (6%) of patients with benign breast disease, 3/53 (6%) of patients with primary breast cancer, and 12/84 (14%) of patients with metastatic breast cancer. Cytosols from 10/56 (18%) primary tumors and 10/37 (28%) metastatic tumors were found to contain the alpha subunit. Comparison of serum and tumor cytosol levels in nine patients with metastatic disease showed a correspondence between elevated cytosol levels and elevated serum levels. No similar correspondence in 25 patients with primary disease was observed. Alpha subunit was isolated from one tumor cytosol and was characterized with respect to its immunochemical cross-reactivity and molecular weight as compared with native alpha subunit from hCG. For both parameters, the native and ectopic alpha subunit were found to be identical.
Subject(s)
Breast Neoplasms/analysis , Chorionic Gonadotropin/analysis , Cytosol/analysis , Breast Neoplasms/secondary , Chorionic Gonadotropin/blood , Electrophoresis, Polyacrylamide Gel , Female , Follicle Stimulating Hormone/analysis , Humans , Luteinizing Hormone/analysis , RadioimmunoassayABSTRACT
The screening of a series of 11 metastatic breast tumors for the presence of the placental isoenzyme of alkaline phosphatase (EC3.1.3.1) by RIA revealed one strong producer. The alkaline phosphatase of this tumor was characterized with respect to its immunochemical cross-reactivity, inhibition by L-phenylalanine and levamisole, subunit molecular weight (Mr) and isoelectric point (pl) in two-dimensional electrophoresis, and one-dimensional peptide map. In all parameters of the characterization, the tumor alkaline phosphatase, except for subunit molecular weight which was slightly lower (60,000 versus 64,000 for the placental isoenzyme). No strong placental alkaline phosphatase producers were found among 16 primary tumors examined by RIA. The screening of patients' sera for the placental alkaline phosphatase using RIA indicated elevated levels over post-menopausal controls in 20% of the metastatic patients. Only 3% of the primary patients had elevated serum levels. These results suggest that the placental isoenzyme of alkaline phosphatase may be a useful tumor marker for recurrent breast cancer.
