Transforming growth factor alpha is a target for the von Hippel-Lindau tumor suppressor.
The von Hippel-Lindau (VHL) tumor suppressor gene has a critical role in the pathogenesis of clear cell renal cell carcinoma (RCC), because VHL mutations have been found in both VHL disease-associated and sporadic RCC. Overexpression of transforming growth factor (TGF)-alpha has been observed in numerous RCC tumors and cell lines, and TGF-alpha has been demonstrated to support RCC cell growth through an autocrine loop. We demonstrate here that VHL substantially decreases TGF-alpha message and protein by shortening TGF-alpha mRNA half-life. By Northern analysis TGF-alpha mRNA steady-state levels were suppressed 5-fold in permanent 786-0 RCC cell lines expressing wild-type VHL compared with 786-0 cells expressing an empty vector or a mutant VHL protein lacking COOH-terminal residues 116-213 (deltaVHL). By Western analysis, VHL also substantially down-regulated the unprocessed, cell-associated Mr 20,000 TGF-alpha protein. Moreover, secreted TGF-alpha was undetectable in VHL-expressing cells. In contrast, VHL did not down-regulate the TGF-alpha receptor, epidermal growth factor receptor, either at the mRNA or protein level. Nuclear run-on in vitro transcription experiments in 786-0 cells showed that VHL did not affect transcriptional control of the endogenous TGF-alpha gene. However, actinomycin D experiments revealed a long TGF-alpha mRNA half-life in 786-0 cells that was significantly decreased by wild-type VHL but not by deltaVHL. We have, therefore, identified TGF-alpha, an important growth factor for RCC, as a new target gene for VHL and demonstrated that VHL acts by decreasing TGF-alpha mRNA stability.
Knebelmann
B
B
Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA.
Ananth
S
S
Cohen
H T
HT
Sukhatme
V P
VP
D015152:Blotting, Northern; D002292:Carcinoma, Renal Cell / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D015536:Down-Regulation; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism; D016147:Genes, Tumor Suppressor / Q000502:physiology*; D006207:Half-Life; D006801:Humans; D007680:Kidney Neoplasms / Q000235:genetics / Q000378:metabolism*; D008025:Ligases; D011506:Proteins / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection; D016211:Transforming Growth Factor alpha / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins; D044767:Ubiquitin-Protein Ligases; D051794:Von Hippel-Lindau Tumor Suppressor Protein
D011506:Proteins; D012333:RNA, Messenger; D016211:Transforming Growth Factor alpha; D025521:Tumor Suppressor Proteins; D044767:Ubiquitin-Protein Ligases; D051794:Von Hippel-Lindau Tumor Suppressor Protein; D066246:ErbB Receptors; D008025:Ligases; C497446:VHL protein, human