Jose M López-Novoa | PubMed Health

PubMed2006

Reduced tumor growth and angiogenesis in endoglin-haploinsufficient mice.

Endoglin is a transforming growth factor-beta(1) (TGF-beta(1)) accessory receptor which is highly expressed in tumor vessels. To study the role of endoglin in tumor growth and angiogenesis we induced a highly vascularized tumor in mice heterozygous for endoglin (Eng+/-) and in their control littermates (Eng+/+) by injecting 10(6) Lewis lung carcinoma (3LL) cells subcutaneously. Nine days after injection, the tumor was removed and weighed. Capillary density (CD31 immunohistochemistry), hemoglobin content and vascular cell adhesion molecule-1 (VCAM-1) expression were used to assess tumor vascularization. Tumor perfusion rate was measured by laser-Doppler technique. Expression of the hypoxia-inducible factor (HIF), endothelial nitric oxide synthase (eNOS) and vascular endothelial growth factor (VEGF) were determined by Western blot analysis. The aerobic metabolism and oxygen dependency were inferred from the measurement of ATP in tumoral tissue. Tumor weight, capillary density, hemoglobin and VCAM-1 were reduced by about 30% in Eng+/- compared to Eng+/+ littermates. The protein levels of eNOS and phosphorylated eNOS were significantly reduced in Eng+/- compared to Eng+/+ mice. HIF expression was slightly reduced whereas VEGF level was slightly increased in Eng+/- compared to Eng+/+. Tumor tissue levels of ATP and ADP were similar in both types of mice. These data demonstrate that endoglin plays a major role in tumor neoangiogenesis.

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PubMed2006

Endoglin regulates cyclooxygenase-2 expression and activity.

The endoglin heterozygous (Eng(+/-)) mouse, which serves as a model of hereditary hemorrhagic telangiectasia (HHT), was shown to express reduced levels of endothelial NO synthase (eNOS) with impaired activity. Because of intricate changes in vasomotor function in the Eng(+/-) mice and the potential interactions between the NO- and prostaglandin-producing pathways, we assessed the expression and function of cyclooxygenase (COX) isoforms. A specific upregulation of COX-2 in the vascular endothelium and increased urinary excretion of prostaglandin E(2) were observed in the Eng(+/-) mice. Specific COX-2 inhibition with parecoxib transiently increased arterial pressure in Eng(+/-) but not in Eng(+/+) mice. Transfection of endoglin in L6E9 myoblasts, shown previously to stimulate eNOS expression, led to downregulation of COX-2 with no change in COX-1. In addition, COX-2 promoter activity and protein levels were inversely correlated with endoglin levels, in doxycyclin-inducible endothelial cells. Chronic NO synthesis inhibition with N(omega)-nitro-l-arginine methyl ester induced a marked increase in COX-2 only in the normal Eng(+/+) mice. N(omega)-nitro-l-arginine methyl ester also increased COX-2 expression and promoter activity in doxycyclin-inducible endoglin expressing endothelial cells, but not in control cells. The level of COX-2 expression following transforming growth factor-beta1 treatment was less in endoglin than in mock transfected L6E9 myoblasts and was higher in human endothelial cells silenced for endoglin expression. Our results indicate that endoglin is involved in the regulation of COX-2 activity. Furthermore, reduced endoglin levels and associated impaired NO production may be responsible, at least in part, for augmented COX-2 expression and activity in the Eng(+/-) mice.

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