Little is known about the involvement of Smad-related molecules in the regulation of the Transforming Growth Factor (TGF)-beta signaling pathway during hepatocarcinogenesis, particularly with respect to preneoplastic lesions of a rat liver. The aims of this study were to investigate the localizations and temporal expressions of TGF-beta Receptor Type 1 (TGR1) and Smads during the promotion stage of chemical hepatocarcinogenesis in rats. We investigated expressions and localizations of TGR1, Smad2, Smad4, and Smad7 by using semi-quantitative RT-PCR and immunohistochemistry in preneoplastic lesions during rat chemical hepatocarcinogenesis induced by Solt and Farber's method. The down-regulation of TGR1, Sma-d2, and Smad4 was evident during the later steps of the promotion stage of chemical hepatocarcinogenesis. In contrast with other Smads, increased Smad7 expression was evident during the later steps of the promotion stage. Also immunohistochemistry revealed that the main site of TGR1, Smad2, Smad4, and Smad7 expression was mainly in hepatocytes of the preneoplastic lesions of a rat liver. Dysregulation of the downstream effectors of TGF-beta such as TGR1, Smad2, Smad4 and, Smad7 might contribute to the progression of preneoplastic lesions during chemical hepatocarcinogenesis in a rat.
Activin Receptors, Type I/*biosynthesis ; Animals ; Apoptosis ; DNA-Binding Proteins/*biosynthesis ; Disease Progression ; Glutathione Transferase/metabolism ; Immunohistochemistry ; In Situ Nick-End Labeling ; Liver/metabolism ; Liver Neoplasms/chemically induced ; Male ; Peptides/chemistry ; RNA, Messenger/metabolism ; Rats ; Rats, Sprague-Dawley ; Receptors, Transforming Growth Factor beta/*biosynthesis ; Reverse Transcriptase Polymerase Chain Reaction ; Signal Transduction ; Time Factors ; Trans-Activators/*biosynthesis

OBJECTIVETo study transforming growth factor-beta1 (TGF-beta1) autoproduction in keloid fibroblasts and the regulation effect of blocking TGF-beta intracellular signaling on rhTGF-beta1 autoproduction.

METHODSKeloid fibroblasts cultured in vitro were treated with either rhTGF-beta1 (5 ng/ml) or recombinant adenovirus containing a truncated type II TGF-beta receptor gene (50 pfu/cell). Their effects of regulating gene expression of TGF-beta1 and its receptor I and II were observed with Northern blot.

RESULTSrhTGF-beta1 up-regulated the gene expression of TGF-beta1 and receptor I, but not receptor II. Over-expression of the truncated receptor II down-regulated the gene expression of TGF-beta1 and its receptor I, but not receptor II.

CONCLUSIONSTGF-beta1 autoproduction was observed in keloid fibroblasts. Over-expression of the truncated TGFbeta receptor II decreased TGF-beta1 autoproduction via blocking TGF-beta receptor signaling.

Activin Receptors, Type I ; biosynthesis ; pharmacology ; Cells, Cultured ; Down-Regulation ; Fibroblasts ; drug effects ; metabolism ; Gene Expression ; Humans ; Keloid ; metabolism ; Protein-Serine-Threonine Kinases ; RNA, Messenger ; genetics ; metabolism ; Receptors, Transforming Growth Factor beta ; biosynthesis ; metabolism ; Sensitivity and Specificity ; Signal Transduction ; Trans-Activators ; metabolism ; Up-Regulation