title: Tenascin-X expression in tumor cells and fibroblasts: glucocorticoids as negative regulators in fibroblasts.
abstract: Tenascin-X has recently been shown to be a novel member of the tenascin family and its distribution is often reciprocal to that of tenascin-C in the developing mouse embryo. We have investigated the expression of tenascin-X in fibroblasts and carcinoma cells in culture. Tenascin-X protein was secreted in vitro in the conditioned media at an apparent molecular mass of approximately 450 kDa. In addition fibroblasts contained a major tenascin-X isoform of 220 kDa. On northern blots, a single major transcript with a size of approximately 13 kb was detected. No overexpression of tenascin-X protein was found in primary fibroblasts of the tenascin-C-gene knockout mice. Steroid hormone glucocorticoids, were found to downregulate tenascin-X mRNA levels and protein synthesis in fibroblasts but not carcinoma cells at physiological concentrations. None of the growth factors or cytokines examined affected the expression level of tenascin-X. As in vivo study, carcinoma cells were transplanted into nude mice. In contrast to the ubiquitous presence of tenascin-X in adult skin, expression of tenascin-X protein during tumorigenesis was found to be down-regulated considerably not only in tumor cells themselves but also in tumor stroma. These findings provide evidence that the expression of tenascin-X can be influenced by stromal-epithelial interactions. We have identified glucocorticoids as physiological inhibitors of tenascin-X and suggest that glucocorticoids may in part participate in the downregulation of tenascin-X in fibroblasts in vivo.
authors.affiliation: Division of Hemopoiesis, Jichi Medical School, Tochigi, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Sakai
authors.forename: Y
authors.initials: Y
authors.lastname: Furukawa
authors.forename: R
authors.initials: R
authors.lastname: Chiquet-Ehrismann
authors.forename: M
authors.initials: M
authors.lastname: Nakamura
authors.forename: S
authors.initials: S
authors.lastname: Kitagawa
authors.forename: T
authors.initials: T
authors.lastname: Ikemura
authors.forename: K
authors.initials: K
authors.lastname: Matsumoto
mesh_terms: D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D015536:Down-Regulation / Q000187:drug effects; D005109:Extracellular Matrix / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D005938:Glucocorticoids / Q000494:pharmacology*; D066298:In Vitro Techniques; D007668:Kidney / Q000166:cytology / Q000187:drug effects; D051379:Mice; D008819:Mice, Nude; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D019063:Tenascin / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D005938:Glucocorticoids; D012333:RNA, Messenger; D019063:Tenascin; C081865:tenascin X