transforming-growth-factor-alpha and Teratoma

The division, differentiation, and function of stem cells and multipotent progenitors are influenced by complex signals in the microenvironment, including oxygen availability. Using a genetic "knock-in" strategy, we demonstrate that targeted replacement of the oxygen-regulated transcription factor HIF-1alpha with HIF-2alpha results in expanded expression of HIF-2alpha-specific target genes including Oct-4, a transcription factor essential for maintaining stem cell pluripotency. We show that HIF-2alpha, but not HIF-1alpha, binds to the Oct-4 promoter and induces Oct-4 expression and transcriptional activity, thereby contributing to impaired development in homozygous Hif-2alpha KI/KI embryos, defective hematopoietic stem cell differentiation in embryoid bodies, and large embryonic stem cell (ES)-derived tumors characterized by altered cellular differentiation. Furthermore, loss of HIF-2alpha severely reduces the number of embryonic primordial germ cells, which require Oct-4 expression for survival and/or maintenance. These results identify Oct-4 as a HIF-2alpha-specific target gene and indicate that HIF-2alpha can regulate stem cell function and/or differentiation through activation of Oct-4, which in turn contributes to HIF-2alpha's tumor promoting activity.

Topics: Alleles; Animals; Basic Helix-Loop-Helix Transcription Factors; Cell Hypoxia; Cell Transformation, Neoplastic; Down-Regulation; Embryonic Development; Female; Immunohistochemistry; Mice; Mice, Nude; Models, Genetic; Octamer Transcription Factor-3; Pregnancy; RNA, Messenger; Stem Cells; Teratoma; Transforming Growth Factor alpha; Vascular Endothelial Growth Factor A

Hypoxia-inducible factors (HIF) are essential transcriptional regulators that mediate adaptation to hypoxic stress in rapidly growing tissues such as tumors. HIF activity is regulated by hypoxic stabilization of the related HIF-1alpha and HIF-2alpha subunits, which are frequently overexpressed in cancer cells. To assess the relative tumor-promoting functions of HIF-1alpha and HIF-2alpha directly, we replaced HIF-1alpha expression with HIF-2alpha by creating a novel "knock-in" allele at the Hif-1alpha locus through homologous recombination in primary murine embryonic stem cells. Compared with controls, s.c. teratomas derived from knock-in embryonic stem cells were larger and more proliferative, had increased microvessel density, and exhibited increased expression of vascular endothelial growth factor, transforming growth factor-alpha, and cyclin D1. These and other data indicate that HIF-2alpha promotes tumor growth more effectively than HIF-1alpha in multiple contexts.

Topics: Alleles; Animals; Basic Helix-Loop-Helix Transcription Factors; Cell Differentiation; Cell Growth Processes; Cell Transformation, Neoplastic; Embryo, Mammalian; Hypoxia-Inducible Factor 1, alpha Subunit; Mice; Mice, Nude; Neovascularization, Pathologic; Stem Cells; Teratoma; Trans-Activators; Transcription Factors; Transforming Growth Factor alpha; Vascular Endothelial Growth Factor A

The aim of the present study was to define the conditions of preparation and in vitro culture of embryonic discs allowing proliferation of ES-like cells. G5-6 porcine blastocysts (G0 = day of AI) were cultured in toto; in G10-11 blastocysts, trophectoderm and primitive endoderm were microsurgically removed from embryonic discs (ED) which were cultured either on plastic or on a feeder layer. Feeder cells were foetal G30 porcine fibroblasts which had been previously irradiated. Culture medium was DMEM supplemented with 0.1 mM beta-mercaptoethanol, 5% foetal calf serum, 5% Ultroser G and 10(3) IU LIF; cultures were performed at 38 degrees C. Colonies were reseeded weekly. Few embryonic discs from G5-6 and no elongating blastocysts gave rise to ES-like cells. At least 50% G10-11 ED attached and developed multilayered colonies (100 cells) of small ovoid ES-like cells. Colonies from 4 sows were maintained in culture for at least 8 wk. Addition of PDGF, insulin or both, induced a transitory stimulation of growth in G6 or G10-11 ED; TGF beta did not modify growth of G6 ICM. Uterine G10-11 flushing medium or retinol induced differentiation of ES-like cells. These cells introduced in nude mice induced teratoma.

Topics: Animals; Blastocyst; Cell Differentiation; Cell Division; Cells, Cultured; Culture Media; Culture Techniques; Fibroblasts; Insulin; Mice; Mice, Nude; Platelet-Derived Growth Factor; Stem Cell Transplantation; Stem Cells; Swine; Teratoma; Transforming Growth Factor alpha; Vitamin A

The varying tumorbiological behaviour of ovarian carcinomas probably influences operability, response to chemotherapy, being one of the most relevant prognostic factors. Because it is believed that an activation of the epidermal growth factor/transforming growth factor alpha (EGF/TGF alpha) signal pathway could be involved, we analysed the expression of epidermal growth factor receptor (EGFR) and TGF alpha with molecular-chemical, biochemical and immunohistochemical methods in 42 ovarian carcinomas, 4 ovarian metastasis, 2 other malignant ovarian tumours, and in 25 nonmalignant tissues (ovary, myometrium). No major rearrangements or amplification of the EGFR or TGF alpha genes were found. In non-malignant tissues no strong EGFR or TGF alpha signals were detected. TGF alpha is mainly produced by the tumour cells as shown by immunohistochemistry. Four different high molecular weight forms (20-48 kD) were detected in malignant tissues by western blot analysis.

Topics: Blotting, Northern; Blotting, Southern; Blotting, Western; Carcinoma; DNA, Neoplasm; ErbB Receptors; Female; Humans; Immunohistochemistry; Ovarian Neoplasms; Placenta; Pregnancy; RNA, Messenger; Sarcoma; Teratoma; Transforming Growth Factor alpha