Publication:

TGF-β1 acts as a tumor suppressor of human malignant keratinocytes independently of Smad 4 expression and ligand-induced G1 arrest (2002)

Author(s): Paterson IC; Davies M; Stone A; Huntley S; Smith E; Pring M; Eveson JW; Robinson CM; Parkinson EK; Prime SS

  • : TGF-beta1 acts as a tumor suppressor of human malignant keratinocytes independently of Smad 4 expression and ligand-induced G(1) arrest

Abstract: This study examined the role of TGF-beta1 in human keratinocyte malignancy. Two carcinoma-derived human oral keratinocyte cell lines, BICR 31 and H314, were selected on the basis of their known resistance to TGF-beta1-induced G(1) arrest, the presence of wild type TGF-beta cell surface receptors and normal Ras. Smad 4 protein was undetectable in both cell lines, but Smad 2 and Smad 3 were expressed at levels comparable with a fully TGF-beta responsive cell line, and treatment of the cells with TGF-beta1 resulted in the phosphorylation of Smad 2. Treatment with exogenous TGF-beta1 resulted in a failure to induce transcription from an artificial Smad-dependent promoter and a failure to down-regulate c-myc, but resulted in an up-regulation of AP-1 associated genes (Fra-1, JunB and fibronectin). Transient transfection of Smad 4 into BICR 31 restored TGF-beta1-induced growth inhibition and Smad-dependent transcriptional activation. Protracted treatment of cells with exogenous TGF-beta1 resulted in the attenuation of cell growth in vitro. To over-express TGF-beta1, both cell lines were transfected with latent TGF-beta1 cDNA; neutralization studies of conditioned media demonstrated that whilst the majority of the peptide was in the latent form, a small proportion was present as the active peptide. Cells that over-expressed endogenous TGF-beta1 grew more slowly in vitro compared to both the vector-only controls and cells that did not over-express the peptide. Orthotopic transplantation of cells that over-expressed endogenous TGF-beta1 to the floor of the mouth in athymic mice resulted in marked inhibition of primary tumor formation compared to controls. Expression of a dominant-negative TGF-beta type II receptor in cells that over-expressed endogenous TGF-beta1 resulted in enhanced cell growth in vitro and diminished the tumor suppressor effect of the ligand in vivo, indicating that the endogenous TGF-beta1 was acting in an autocrine capacity. The results demonstrate that over-expression of endogenous TGF-beta1 in human malignant oral keratinocytes leads to growth inhibition in vivo and tumor suppression in vitro by mechanisms that are independent of Smad 4 expression and TGF-beta1-induced G(1) arrest.

Notes: Journal Article

  • Type of Article: Short report
  • Short Title: TGF-beta1 acts as a tumor suppressor of human malignant keratinocytes independently of Smad 4 expression and ligand-induced G(1) arrest
  • Date: 2002-02-28
  • Journal: Oncogene
  • Volume: 21
  • Issue: 10
  • Pages: 1616-1624
  • Publisher: Nature Publishing Group
  • Publication type: Article
  • Bibliographic status: Published

Keywords: Animals Carcinoma/ metabolism/pathology Cell Division DNA-Binding Proteins/genetics/ metabolism G1 Phase Humans Keratinocytes/metabolism Kinetics Ligands Mice Mice, Nude Mouth Neoplasms/metabolism/pathology Neoplasm Transplantation RNA, Neoplasm/biosynthesis Skin Neoplasms/ metabolism/pathology Trans-Activators/genetics/ metabolism Transcription, Genetic Transfection Transforming Growth Factor beta/genetics/pharmacology/ physiology Tumor Cells, Cultured Tumor Suppressor Proteins/genetics/pharmacology/ physiology

Staff

Dr Max Robinson
Senior Lecturer in Oral Pathology