Showing papers by "Raphael Kopan published in 1988"

Human papillomavirus type 16 alters human epithelial cell differentiation in vitro.

Abstract: Human papillomavirus (HPV) types 16, 18, 31, and 33 have been implicated as etiologic agents of cervical and penile cancer. Using a cell culture system for keratinocytes which allows stratification and production of differentiation-specific keratins, we have examined the effects of one of these viruses, HPV-16, on the differentiation capabilities of human epithelial cells. A plasmid containing the HPV-16 genome and a neomycin-selectable marker was transfected into primary human epidermal cells and SCC-13 cells, an immortalized squamous cell carcinoma cell line. Cloned neomycin-resistant cell lines were isolated and examined by cell culture on raised collagen rafts. Cell lines containing HPV-16 DNA retained the ability to stratify and express differentiation-specific keratins in the raft system but otherwise failed to differentiate normally. The histological abnormalities induced by HPV-16 closely resembled those seen in genital intraepithelial neoplasia in vivo. Hence, our results support the role of HPV-16 as an etiologic agent in the development of genital neoplasias and suggest a specific system for the study of HPV-16-induced epithelial cancers.

Use of monospecific antisera and cRNA probes to localize the major changes in keratin expression during normal and abnormal epidermal differentiation

Abstract: We report here the isolation and characterization of three antisera, each of which is specific for a single keratin from one of the three different pairs (K1/K10, K14/K5, K16/K6) that are differentially expressed in normal human epidermis and in epidermal diseases of hyperproliferation. We have used these antisera in conjunction with monospecific cRNA probes for epidermal keratin mRNAs to investigate pathways of differentiation in human epidermis and epidermal diseases in vivo and in epidermal cells cultured from normal skin and from squamous cell carcinomas in vitro. Specifically, our results suggest that: (a) the basal-specific keratin mRNAs are down-regulated upon commitment to terminal differentiation, but their encoded proteins are stable, and can be detected throughout the spinous layers; (b) the hyperproliferation-associated keratin mRNAs are expressed at a low level throughout normal epidermis when their encoded proteins are not expressed, but are synthesized at high levels in the suprabasal layers of hyperproliferating epidermis, coincident with the induced expression of the hyperproliferation-associated keratins in these cells; and (c) concomitantly with the induction of the hyperproliferation-associated keratins in the suprabasal layers of the epidermis is the down-regulation of the expression of the terminal differentiation-specific keratins. These data have important implications for our understanding of normal epidermal differentiation and the deviations from this process in the course of epidermal diseases of hyperproliferation.

The Differential Expression of Keratin Genes in Human Epidermal Cells

Abstract: Terminal differentiation in human epidermis is a complex process involving a number of morphological and biochemical changes. The major differentiation-specific markers are the keratins, a group of proteins (M.W. 40–70K) which are present in all epithelial cells and which self-assemble into 8 nm cytoskeletal filaments. As a basal epidermal cell undergoes a commitment to terminally differentiate, it changes the pattern of keratins that it makes, switching to the synthesis of a set of keratins whose filaments have a propensity to aggregate. During wounding, or when skin is placed into tissue culture, the keratinization-specific keratins are suppressed, and a new set of keratins is induced. To elucidate the functional significance of these changes in keratin patterns, we have begun to examine the molecular mechanisms which orchestrate their synthesis in epidermis and in epidermal cells grown in culture. In this review, we discuss some of our more recent experiments aimed at characterizing the expression of the keratin proteins, their mRNAs and their genes in human epidermis.