Glycoprotein synthesis as a function of epithelial cell arrangement: Biosynthesis and release of glycoproteins by human breast and prostate cells in organ culture

Abstract

We demonstrate that a technique is available to investigate glycoprotein synthesis in organ cultures of human breast and prostate surgical specimens where the 3‐dimensional epithelial cell arrangement remains intact. Malignant breast and prostate epithelium maintained their capacity to synthesize glycoproteins for at least 3 days as followed by the incorporation of [³H] glucosamine into macromolecules. Over 70% of incorporation was by malignant cells as judged by autoradiography. Labeled glycoproteins were released into glandular lumina and consequently into the culture fluid. Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis revealed predominantly one group of macromolecules released with an apparent molecular weight of 48,000 ± 6,000 daltons. This glycoprotein was found in all of the breast specimens studied, which included 1 medullary, 1 infiltrating lobular, and 8 infiltrating duct carcinomas. The pattern was independent of the availability of estrogen receptors. A similar glycoprotein was also observed in the culture media from a Grade I and a Grade II well‐differentiated infiltrating prostate carcinoma. Incorporation was below the level of detection in 4 of 6 cases of benign prostatic hyperplasia. A more complex pattern of labeled glycoproteins was found in the media of a Grade II and a Grade III poorly‐differentiated prostate carcinoma. The established human mammary carcinoma cell line MCF‐7 synthesized and released a similar 48,000 molecular weight glycoprotein but additional components with larger molecular weights were also released. An intriguing interpretation that 3‐dimensional tissue integrity restricts some glycorprotein synthesis is discussed. Cells grown in 2‐dimensional monolayers could escape from such a topographic restriction and express additional families of glycoproteins.