transforming-growth-factor-beta and Pheochromocytoma

Genetic studies of families at high risk for developing malignant and benign renal neoplasms led to cloning of genes whose alteration results in tumor formation. These genes are either tumor suppressors (VHL, TSC) or oncogenes (MET). Their significance in understanding oncogenesis extends far beyond the familial syndromes. The identification of these genes and the elucidation of their biochemical functions are likely to facilitate (1) our understanding of the full clinical spectrum of the corresponding diseases, (2) genetic counseling, and (3) rational design of effective strategies to prevent and/or treat familial and sporadic forms of these neoplasms.

Topics: Animals; Carcinoma, Renal Cell; Cloning, Molecular; Elongin; Genes, Tumor Suppressor; Genotype; Humans; Kidney Diseases, Cystic; Kidney Neoplasms; Ligases; Middle Aged; Models, Genetic; Mutation; Pheochromocytoma; Proteins; Syndrome; Transcription Factors; Transforming Growth Factor beta; Tuberous Sclerosis; Tumor Suppressor Proteins; Ubiquitin-Protein Ligases; von Hippel-Lindau Disease; Von Hippel-Lindau Tumor Suppressor Protein

Conditioned medium from PC12 cells incubated with retinoic acid (RA) increases [3H]thymidine incorporation in normal rat kidney (NRK) fibroblasts and 3D9 epithelial cells. The medium also causes anchorage-independent growth of NRK cells, which is strongly potentiated either in the presence of EGF or after activation of latent forms of transforming growth factors (TGFs) by acidification. These results suggest that RA regulates the release of more than one growth factor by PC12 cells. Conditioned media from control or NGF-treated PC12 cells causes growth of NRK cells in soft agar only after acidification. An increase in expression of the TGF-beta1 gene is coincident with NGF-induced neuronal differentiation of PC12 cells. In addition, RA also causes a dose- and time-dependent increase in content of TGF-beta1 transcripts. This increase is, at least in part, secondary to transcriptional activation. Sequences responsible for the effect of RA and NGF are located in the 5'-flanking region of the TGF-beta1 gene. The TFG-beta1 gene has two promoters and in transient transfection assays RA and NGF significantly enhance the activity of constructs containing the second promoter. High-affinity TGF-beta1 receptors were undetectable in PC12 cells both before and after NGF or RA treatment. RA and NGF decrease PC12 cell proliferation and a neutralizing anti-TGF-beta1 antibody does not reverse this inhibition. In summary, an increase in expression and secretion of TGF-beta1 accompanies RA and NGF-induced PC12 cell growth arrest, but TGF-beta1 does not play an autocrine role in this inhibition.

Topics: Adrenal Gland Neoplasms; Animals; Cell Differentiation; Cell Division; Cell Line; Culture Media, Conditioned; Epidermal Growth Factor; Epithelium; Fibroblasts; Kidney; Kinetics; Mice; Mink; Nerve Growth Factors; Neurons; PC12 Cells; Pheochromocytoma; Rats; Recombinant Proteins; Regulatory Sequences, Nucleic Acid; Transcription, Genetic; Transfection; Transforming Growth Factor beta; Tretinoin

Nerve growth factor (NGF) stimulates the differentiation of PC12 pheochromocytoma cells to those resembling sympathetic neurons. We have investigated whether NGF regulates transforming growth factor (TGF)-beta gene expression and protein secretion in PC12 cells. These cells constitutively express TGF-beta 1 mRNA, whereas TGF-beta 2 and -beta 3 mRNAs are expressed at very low levels. TGF-beta 1 gene expression was stimulated greater than 10-fold when PC12 cells were treated with NGF. Sequences between -119 and -98 in the TGF-beta 1 promoter, homologous to an Egr-1 binding site, were shown to be important for both basal and NGF-induced promoter activity. We also found that a factor(s) present in nuclear extracts from PC12 cells interacted with the sequences between -119 and -98 and that expression of this factor was induced by NGF treatment. Moreover, specific binding to TGF-beta 1 promoter fragments between -119 and -98 was seen using the bacterially expressed transcription factor Egr-1. These results indicate that activation of TGF-beta 1 expression is one of the cellular responses of PC12 cells to NGF and suggest that TGF-beta may play a role in the differentiation of sympathetic neurons.

Topics: Adrenal Gland Neoplasms; Animals; Base Sequence; Binding Sites; Blotting, Northern; Cell Nucleus; Chloramphenicol O-Acetyltransferase; DNA-Binding Proteins; Gene Expression; Kinetics; Molecular Sequence Data; Nerve Growth Factors; Oligodeoxyribonucleotides; PC12 Cells; Pheochromocytoma; Plasmids; Promoter Regions, Genetic; RNA, Messenger; RNA, Neoplasm; Transcription Factors; Transcription, Genetic; Transfection; Transforming Growth Factor beta; Zinc Fingers