ABSTRACT
Human fetal development depends on the ability of the embryo to gain access to the maternal circulation. Thus, specialized stem cells of the newly formed placenta, trophoblast, invade the uterus and its arterial network to establish an efficient feto-maternal molecular exchange. To accomplish this task, trophoblast differentiation during the first trimester of pregnancy involves cell proliferation, invasion, and extracellular matrix (ECM) remodelling. Trophoblast invasion shares many features with tumour cell invasion, with the distinction that it is strictly spatially and temporally controlled. We have previously demonstrated that PAR1, the first member of the protease-activated receptor (PAR) family, plays a central role in tumour cell invasion. In the present study we have examined the pattern of expression of PAR1 and other PAR family candidates during early human placental development. We show that PAR1 and PAR3 are highly and spatially expressed between the 7th and 10th weeks of gestation but not at the 12th week and thereafter. Likewise, high expression levels of PAR1 and PAR3 were observed in the cytotrophoblast cells of complete hydatidiform mole as compared to minimal levels in normal age-matched placenta. Together, our data suggest the involvement of PAR1 and PAR3 in restricted and unrestricted pathological trophoblast invasion.
Subject(s)
Placenta/metabolism , Receptors, Thrombin/analysis , Trophoblasts/physiology , Chorionic Villi/metabolism , Down-Regulation/physiology , Extracellular Matrix/metabolism , Female , Humans , Hydatidiform Mole/metabolism , Immunohistochemistry/methods , In Situ Hybridization/methods , Maternal-Fetal Exchange/physiology , Polymerase Chain Reaction/methods , Pregnancy , Pregnancy Proteins/analysis , Pregnancy Trimester, First/physiology , Receptor, PAR-1 , Trophoblasts/cytologyABSTRACT
While protease-activated receptors (PARs) play a traditional role in vascular biology, they emerge with surprisingly new assignments in tumor biology. PAR1 expression correlates with the invasion properties of breast carcinoma, whereas human PAR1 antisense reduces their ability to migrate through Matrigel. Part of the molecular mechanism of PAR1 invasion involves the formation of focal contact complexes on PAR1 activation. PAR1 induces angiogenesis in animal models in vivo and exhibits an oncogenic phenotype of enhanced ductal complexity when overexpressed in mouse mammary glands.
Subject(s)
Epithelial Cells/metabolism , Neoplasm Invasiveness/physiopathology , Neoplasm Metastasis/physiopathology , Receptor, PAR-1/physiology , Animals , Breast/blood supply , Breast/growth & development , Breast Neoplasms/metabolism , Breast Neoplasms/pathology , Cell Division , Cytoskeleton/ultrastructure , Epithelial Cells/pathology , Female , Humans , Integrins/physiology , Mice , Mice, Knockout , Morphogenesis , Neovascularization, Pathologic/physiopathology , Oligonucleotides, Antisense/pharmacology , Placenta/blood supply , Pregnancy , Receptors, Vitronectin/physiology , Thrombin/physiology , Vascular Endothelial Growth Factor A/biosynthesis , Vascular Endothelial Growth Factor A/geneticsABSTRACT
The formation of new blood vessels is a critical determinant of tumor progression. We find that Par1 gene expression plays a central role in blood vessel recruitment in animal models. By in vivo injection of either Matrigel plugs containing Par1-expressing cells or of rat prostatic carcinoma cells transfected with tetracycline-inducible Par1 expression vectors, we show that Par1 significantly enhances both angiogenesis and tumor growth. Several vascular endothelial growth factor (VEGF) splice forms are induced in cells expressing Par1. Activation of PAR1 markedly augments the expression of VEGF mRNAs and of functional VEGFs as determined by in vitro assays for endothelial tube alignment and bovine aortic endothelial cell proliferation. Because neutralizing anti-VEGF antibodies potently inhibited Par1-induced endothelial cell proliferation, we conclude that Par1-induced angiogenesis requires VEGF. Specific inhibitors of protein kinase C (PKC), Src, and phosphatidylinositol 3-kinase (PI3K) inhibit Par1-induced VEGF expression, suggesting the participation of these kinases in the process. We also show that oncogenic transformation by genes known to be part of PAR1 signaling machinery is sufficient to increase VEGF expression in NIH 3T3 cells. These data support the novel notion that initiation of cell signaling either by activating PAR1 or by the activated forms of oncogenes is sufficient to induce VEGF and hence angiogenesis.
Subject(s)
Cell Transformation, Neoplastic , Neoplasms/blood supply , Neovascularization, Pathologic/physiopathology , Receptors, Thrombin/physiology , 3T3 Cells , Animals , Blotting, Northern , Endothelial Growth Factors/genetics , Endothelial Growth Factors/metabolism , Gene Expression , Genes, ras/genetics , Genes, src/genetics , Humans , Intercellular Signaling Peptides and Proteins/genetics , Intercellular Signaling Peptides and Proteins/metabolism , Lymphokines/genetics , Lymphokines/metabolism , Male , Mice , Mice, Inbred BALB C , Neoplasm Transplantation , Neoplasms/genetics , Neoplasms, Experimental/genetics , Neoplasms, Experimental/pathology , Oncogenes/genetics , Phosphatidylinositol 3-Kinases/metabolism , Protein Kinase C/metabolism , RNA, Messenger/genetics , RNA, Messenger/metabolism , Rats , Receptor, PAR-1 , Receptors, Thrombin/genetics , Transfection , Transplantation, Heterologous , Tumor Cells, Cultured , Vascular Endothelial Growth Factor A , Vascular Endothelial Growth Factors , src-Family Kinases/metabolismABSTRACT
OBJECTIVE: The goal of this work was to evaluate the involvement of gonadotropins in the regulation of adhesion of human epithelial ovarian carcinoma. We studied two pathways that were previously implicated in the metastatic implantation of ovarian carcinoma to the peritoneum, namely hyaluronan-CD44 and RGD-integrin mediated adhesion. METHODS: Two cell lines derived from human epithelial ovarian carcinoma (MLS and OC238) were stimulated with luteinizing hormone (LH) and/or follicle stimulating hormone (FSH). Expression of CD44 was evaluated by Western blotting. Expression of alpha(v)-integrins was studied by RT-PCR and Northern blot. Integrin and CD44 mediated adhesion of the cells was analyzed using culture plates coated either with a thrombin derived RGD containing peptide or fibronectin for integrin mediated adhesion or with hyaluronan for CD44 mediated adhesion. RESULTS: MLS cells stimulated with either LH or FSH showed increased adhesion to culture plates coated with hyaluronan, as well as to culture plates coated with fibronectin or with a thrombin derived RGD containing peptide. In these cells, gonadotropin stimulation led to induced expression of the integrin subunit alpha(v) and CD44, the cell surface hyaluronan receptor. On the other hand, OC238 cells showed no expression of the integrin subunit alpha(v) and no hormonal effect on the expression of CD44. Accordingly, adhesion of OC238 cells on either RGD or CD44 was not affected by hormonal stimulation. CONCLUSION: Elevated levels of gonadotropins may in some cases facilitate peritoneal metastatic dissemination of ovarian cancer by increasing cell adhesion, the first essential step in the invasion process.
