Papers by Michelle Letarte
Journal of Immunology, Sep 15, 1988
American Journal of Pathology, Jun 1, 2001
Biochemical Journal, Dec 1, 1988
Biochemical Journal, Sep 1, 1987
Frontiers in Immunology, Mar 20, 2014
PubMed, Sep 15, 2005
Background: Angiogenesis is important in health and several disease states. CD105 is a proliferat... more Background: Angiogenesis is important in health and several disease states. CD105 is a proliferation-associated and hypoxia-inducible transmembrane protein abundantly expressed in angiogenic endothelial cells. CD105 is a receptor for transforming growth factors (TGF)-beta1 and -beta3. The exact mechanisms for CD105 regulation of vascular development have not been fully elucidated. Materials and methods: In this study, an antisense approach to create a murine and a human stably transfected endothelial cell line expressing a reduction in CD105 protein was used. Results: We showed that inhibition of CD105 in cultured murine and human endothelial cells enhanced the ability of TGF-beta1 to suppress growth and migration, and influenced TGF-beta1 promoter activity. TGF-beta1 not only reduced the length of the capillary-like structures, but also caused mortality in CD105-deficient murine antisense cells compared to control cultures. To determine whether CD105 affected TGF-beta1-induced gene expression, a luciferase assay in transiently transfected cells with p3TP-Lux promoter constructs was performed. Both murine and human antisense transfectants showed a significant increase in p3TP-Lux promoter activity. Further studies on the functional importance of CD105 was undertaken in irradiated normoxic and hypoxic cells. The levels of pro- and anti-apoptotic markers were also evaluated. There was an increase in pro-apoptotic marker (p53), but a reduction in anti-apoptotic marker (Bcl-2) in CD105-deficient cells. Conclusion: These results provide direct evidence that CD105 antagonises the inhibitory effects of TGF-beta1 on human and murine vascular endothelial cells and that normal cellular levels of CD105 are required for the formation of new blood vessels.
Proceedings of the National Academy of Sciences of the United States of America, Jun 1, 1987
Developmental Biology, Nov 1, 2009
PubMed, Feb 15, 2000
Steroid hormones have been implicated in the etiology and/or progression of epithelial ovarian ca... more Steroid hormones have been implicated in the etiology and/or progression of epithelial ovarian cancer. As ovarian surface epithelial cells are growth inhibited by transforming growth factor beta (TGF-beta), we tested whether steroid hormones could regulate the expression of TGF-beta1 or its receptors in ovarian cancer cells, as assessed by quantitative reverse transcription-PCR. Treatment of ovarian cancer HEY cells with 500 nM 5alpha-dihydrotestosterone (DHT), but not estradiol-17beta or progesterone, for 60 h down-regulated the expression of mRNA for TGF-beta receptors I and II (TbetaR-I and TbetaR-II), betaglycan, and endoglin but had no effect on TGF-beta1 mRNA levels. Androgen receptor (AR) mRNA expression in HEY cells was compared to other ovarian cancer cell lines. OVCAR-3 cells expressed AR mRNA levels similar to that of androgen-responsive LNCaP prostate cancer cells, whereas SKOV-3 and HEY cells expressed only 3 and 0.01%, respectively. Western blot analysis and saturation binding assays confirmed the expression of AR protein in these three cell lines, but at the limit of detection in SKOV-3 and HEY cells. Treatment of SKOV-3 and HEY cells for 24 h with 1-50 nM DHT resulted in a dose-dependent down-regulation of TbetaR-II mRNA. The AR antagonist hydroxyflutamide did not reverse the effect of DHT on SKOV-3 cells but by itself down-regulated TbetaR-II mRNA. This apparent androgen-mimetic action of hydroxyflutamide and the ability of SKOV-3 and HEY cells to respond to DHT may be due to their expression of AR-associating protein 70, an AR co-activator reported to amplify AR transactivation and to result in agonist activity of AR antagonists. DHT was able to reverse TGF-beta1 growth-inhibitory action in SKOV-3 cells and in a primary culture of ovarian cancer cells derived from ascites. Thus, androgens may promote ovarian cancer progression in part by decreasing TGF-beta receptor levels, thereby allowing ovarian cancer cells to escape TGF-beta1 growth inhibition.
The European respiratory journal, Apr 22, 2009
Molecular Immunology, 1985
Cell and Tissue Research, Apr 23, 1998
Endoglin is a component of the receptor complex for transforming growth factor (TGF)-beta1 and TG... more Endoglin is a component of the receptor complex for transforming growth factor (TGF)-beta1 and TGF-beta3. We analysed its expression by immunohistochemistry in human embryos at 4-8 weeks of gestation and in hearts ranging from 4-13 weeks old. We compared endoglin distribution with that of TGF-beta receptors type I (TbetaR-I), type II (TbetaR-II) and betaglycan. Endoglin was found on endothelial cells in all tissues examined, consistent with its expression in adult blood vessels. TbetaR-I, TbetaR-II and betaglycan were observed on most cell types and had an overall similar pattern of distribution. Endoglin was detected on the endocardium as early as 4 weeks, but was absent from myocardium. It was present at high levels on the endocardial cushion tissue mesenchyme from 5-8 weeks' gestation, during heart septation and valve formation, and subsequently decreased as the valves matured. Endoglin expression in heart extracts was confirmed by Western blot analysis. TbetaR-I, TbetaR-II and betaglycan were mostly found on cardiac myocytes, but were detectable at low levels on endocardium. They were expressed transiently on cushion mesenchyme, albeit at much lower levels than endoglin. All four components of the TGF-beta receptor complex were detected by RT-PCR in embryonic heart. Thus transient up-regulation of the components of the TGF-beta receptor complex, and particulartly of endoglin, is associated with heart septation and valve formation during early human development.
Trends in Cardiovascular Medicine, Oct 1, 2000
Frontiers in Genetics, Feb 13, 2015
PubMed, Dec 1, 1995
We have characterized a murine IgM monoclonal antibody, TEC-11, that recognizes endoglin and may ... more We have characterized a murine IgM monoclonal antibody, TEC-11, that recognizes endoglin and may be suitable for targeting cytotoxic agents to human tumor vasculature. TEC-11 strongly stains endothelial cells in a broad range of solid human tumors while staining endothelial cells in the majority of normal, healthy adult tissues relatively weakly. Human umbilical vein endothelial cells (HUVECs) in sections of the umbilical vein react weakly with TEC-11, whereas proliferating HUVECs in tissue culture react strongly and uniformly. HUVEC cultures grown to confluence and then rested contain two subpopulations having high and low levels of endoglin expression. Flow cytometry revealed that a significant proportion of cells with high endoglin expression are cycling, having markedly increased levels of cellular protein, RNA, and DNA by comparison to low endoglin-expressing cells, which appear to be noncycling. Taken together, the increased binding of TEC-11 to tumor vasculature and to dividing as opposed to noncycling HUVECs in vitro suggests that endoglin is an endothelial cell proliferation-associated marker. An immunotoxin [TEC-11.deglycosylated ricin A chain (dgA)] composed of TEC-11 and dgA was 3000-fold more potent at inhibiting protein synthesis in proliferating HUVEC cultures than in confluent cultures. The confluent cells were no more sensitive to TEC-11.dgA than they were to an isotype-matched immunotoxin of irrelevant specificity. These findings suggest that TEC-11.dgA might have therapeutic value in the treatment of solid tumors in humans by selectively killing dividing endothelial cells which are prevalent in such tumors.
Journal of Biological Chemistry, Jul 1, 2005
Journal of Clinical Investigation, Nov 15, 1999
Human Immunology, Aug 1, 1985
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Papers by Michelle Letarte