TYPE-VIII COLLAGEN - SYNTHESIS BY NORMAL AND MALIGNANT-CELLS IN CULTURE

  • 1 January 1984
    • journal article
    • research article
    • Vol. 50  (2) , 219-231
Abstract
A novel protein belonging to the collagen family was originally purified from the culture medium of bovine aortic endothelial cells. This endothelial collagen, termed EC, also comprises the major collagen type synthesized by a malignant astrocytoma-derived cell line [human U-251 MG cells]. Examination of several cell strains derived from normal tissues revealed that EC was not synthesized by all endothelial cells; it was absent from human endothelial cells cultured from both large and small vessels but was present in bovine cells, including those from capillaries. Human foreskin fibroblasts also secreted this protein in small amounts relative to interstitial procollagens, but it was not detected in 2 human epithelial cell strains. EC was consistently observed in human cell lines derived from several carcinomas and comprised the major collagenous protein secreted by cells cultured from a Ewing''s sacroma. Malignant or transformed murine cells did not produce EC in vitro. The protein was not apparent after metabolic labeling of human cells from an epidermoid carcinoma, a fibrosarcoma, and 2 Wilms'' tumors. EC-like proteins were isolated from cell culture medium by ion-exchange chromatography and were compared by sodium dodecyl sulfate-polyacrylamide gel electrophoresis after cleavage with vertebrate collagenase, mast cell protease and CNBr [cyanogen bromide]. In addition to the homologies displayed by comparative peptide mapping, these collagens exhibited other unusual properties that collectively were characteristic of EC from endothelial and astrocytoma-derived cells. The studies support the existence of a novel class of collagenous proteins that are secreted by a wide variety of cells derived from both normal and neoplastic tissues. The class of proteins, which manifests several unusual structural characteristics, was designated type VIII collagen.