Role of the Phosphatidylinositol-3-Kinase and Extracellular Regulated Kinase Pathways in the Induction of Hypoxia-Inducible Factor (HIF)-1 Activity and the HIF-1 Target Vascular Endothelial Growth Factor in Ovarian Granulosa Cells in Response to Follicle-Stimulating Hormone

The aim of the present study was to explore the potential mechanism underlying stathmin 1 (Stmn1) regulation of embryo implantation, as a continuation of previous proteomic research. Adult healthy female mice were mated naturally with fertile males. Murine uterine tissue was collected during the peri-implantation period. Local expression of Stmn1 during embryo implantation was detected by immunohistochemistry (IHC), which showed that Stmn1 was extensively expressed in endometrial glandular epithelium, vascular endothelium, luminal epithelium and the underlying stromal cells at the implantation site on Day 5. The role of Stmn1 during embryo implantation was evaluated by transient knockdown of Stmn1 in vivo using short interference (si) RNA, and some associated factors including Akt, phosphorylated (p-) Akt, hypoxia-inducible factor (HIF)-1α, prolactin (PRL), insulin-like growth factor binding protein (IGFBP) 1 and vascular endothelial growth factor (VEGF) were examined by western blotting analysis and ELISA. The number of embryos implanted after Stmn1-siRNA infusion into the lumen of one uterine horn was lower than that with normal pregnancies (2.2 ± 1.5 vs 8.6 ± 0.5 respectively; P < 0.05). The expression of VEGF, HIF-1α, p-Akt and the decidualisation biomarkers PRL and IGFBP 1 was upregulated at the implantation site on Day 5, but downregulated after Stmn1-siRNA infusion. These findings suggest that during embryo implantation, knockdown of Stmn1 suppresses decidualisation by inhibiting the expression of p-Akt, HIF-1α and VEGF, thus leading to impaired embryo implantation. These findings provide clues for understanding the complicated process of embryo implantation and the potential role of Stmn1 during embryo implantation.

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Induction of Vascular Endothelial Growth Factor by Hypoxia Is Modulated by a Phosphatidylinositol 3-Kinase/Akt Signaling Pathway in Ha-ras-Transformed Cells Through a Hypoxia Inducible Factor-1 Transcriptional Element

Blood ◽

10.1182/blood.v90.9.3322 ◽

1997 ◽

Vol 90 (9) ◽

pp. 3322-3331 ◽

Cited By ~ 335

Author(s):

Nathalie M. Mazure ◽

Eunice Y. Chen ◽

Keith R. Laderoute ◽

Amato J. Giaccia

Keyword(s):

Vascular Endothelial Growth Factor ◽

Growth Factor ◽

Tumor Microenvironment ◽

Kinase Activity ◽

Hypoxia Inducible Factor ◽

Transformed Cells ◽

Vascular Endothelial ◽

Phosphatidylinositol 3 Kinase ◽

Hypoxia Inducible Factor 1 ◽

Endothelial Growth Factor

Abstract Tumor angiogenesis, the development of new blood vessels, is a highly regulated process that is controlled genetically by alterations in oncogene and tumor suppressor gene expression and physiologically by the tumor microenvironment. Previous studies indicate that the angiogenic switch in Ras-transformed cells may be physiologically promoted by the tumor microenvironment through the induction of the angiogenic mitogen, vascular endothelial growth factor (VEGF). In this report, we show Ras-transformed cells do not use the downstream effectors c-Raf-1 or mitogen activated protein kinases (MAPK) in signaling VEGF induction by hypoxia as overexpression of kinase-defective alleles of these genes does not inhibit VEGF induction under low oxygen conditions. In contrast to the c-Raf-1/MAP kinase pathway, hypoxia increases phosphatidylinositol 3-kinase (PI 3-kinase) activity in a Ras-dependent manner, and inhibition of PI 3-kinase activity genetically and pharmacologically results in inhibition of VEGF induction. We propose that hypoxia modulates VEGF induction in Ras-transformed cells through the activation of a stress inducible PI 3-kinase/Akt pathway and the hypoxia inducible factor-1 (HIF-1) transcriptional response element.

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