A preliminary investigation into prolactin receptors in human breast carcinomas provided strong evidence that specific binding of prolactin was occurring in at least three of the nine specimens examined (eight human breast carcinomas and one scalp metastasis). These "prolactin receptor positive" tumors were all from premenopausal patients. Three of the tumors of postmenopausal women also suggested the occurrence of specific prolactin binding but, as saturation of the receptors had not been achieved in these assays, the results require confirmation. Some general trends in the binding characteristics of the tumors of premenopausal and postmenopausal patients were also observed.Cancer 43:643-646, 1979.T taining the growth of experimentally induced rat mammary tumors has previously been reported.3'8~"2"7 These observations have been supported by evidence of prolactin binding sitess*6+11,21 in such tumors. Evidence for prolactin dependence of human breast carcinomas was first reported by Salih et ~1 . '~ when they found in the tissue cultures of 16 out of 50 human breast carcinomas, an enhanced dehydrogenase activity if prolactin was added to the medium. Subsequently, Barrett at a!. ' observed regression of metastatic breast carcinoma in one patient after hypophysectomy and termination of pregnancy. The tumor had been found to be prolactin, growth hormone and human placental lactogen dependent in the Salih system. We report the examination of eight primary humnn breast carcinomas and one secondary human breast carcinoma (scalp), which revealed evidence for the presence of prolactin binding sites.
MATEKIALS A N D METHODSThe ovine prolactin (NIH-P-S-1 l), which was kindly supplied by the Endocrine Study Section, Institute of Arthritis, Metabolic and Digestive Diseases, Bethesda, MD, was la- belled with lZ5-I using a method based on the Greenwood P t ~1 . " oxidative chloramine T procedure. The entire reaction was carried out in the isotope vial. 20 p1 of 0 . 5~ phosphate buffer, pH 7.4 was added to 1 pg of o-PRL which in turn was added to 0.5 mCi of Na lZ5I and vortexed. 10 pI of chloramine T solution (2.5 mg/2mlO.O5~ phosphate buffer, pH 7.4) was added, vortexed for three seconds and left to stand for 15 seconds before adding 25 pl of sodium metabisulphite solution (2.5 mg/ml 0 . 0 5~ phosphate buffer) followed by 200 pl of 5% bovine serum albumin in 0 . 0 5~ barbitone-barbitone sodium buffer, pH 8.6. The reaction vial was vortexed following each of these additions. Purification of the products was affected by column chromatography using a 0.9 x 90 cm column of Sephadex G-1 00. Before use, 1 ml 10% bovine serum albumin in 0 . 0 7~ barbitone buffer, pH 8.6 was added and allowed to pass at least 10 cm down the column. Elution was carried out with 0 . 0 7~ barbitone buffer pH 8.6, under positive pressure provided by a peristaltic pump. 1 ml fractions were collected in tubes containing 1 ml of 1% bovine serum albumin in 0 . 0 1~ phosphosaline buffer, pH 7.4 [Na2HP0, (1.14g), KH,PO, (0.267g), NaCl (8.768) in 1000 ml distil...
