Purification of an anemia-inducing factor from human placenta and its application to diagnosis of malignant neoplasms

An anemia-inducing substance was isolated from the human placenta and designated placental anemia-inducing factor (PAIF). An amount of 2.8 mg was purified from about 70 total placentas (total wet weight, 42 kg). PAIF caused hemolysis of human erythrocytes in vitro and reduced the number of erythrocytes in rabbits to 80% of that in the control by i.v. administration of 27 micrograms/kg of body weight. PAIF is a glycoprotein with a molecular weight of about 20,000 and containing about 56% sugar. Radioimmunoassay using 125I-labeled PAIF and antiserum revealed a common antigenicity with crude anemia-inducing substance in sera from patients with cancer. No cross-reactions were observed between PAIF and alpha-fetoprotein, carcinoembryonic antigen, Australia antigen, human chorionic gonadotropin, or human placental lactogen. The level of anemia-inducing factor in normal serum was less than 100 ng/ml, whereas 43 of 63 cancer patients (68.3%) had over 100 ng/ml of serum anemia-inducing factor. Anemia-inducing factor assay may provide a means of detection and aid in the treatment of malignant diseases.