Angiogenesis is a complex process, requiring a finely tuned balance between numerous stimulatory and inhibitory signals. ALK1 (activin receptor like-kinase 1) is an endothelial-specific type 1 ...receptor of the transforming growth factor-β receptor family. Heterozygotes with mutations in the ALK1 gene develop hereditary hemorrhagic telangiectasia type 2 (HHT2). Recently, we reported that bone morphogenetic protein (BMP)9 and BMP10 are specific ligands for ALK1 that potently inhibit microvascular endothelial cell migration and growth. These data lead us to suggest that these factors may play a role in the control of vascular quiescence. To test this hypothesis, we checked their presence in human serum. We found that human serum induced Smad1/5 phosphorylation. To identify the active factor, we tested neutralizing antibodies against BMP members and found that only the anti-BMP9 inhibited serum-induced Smad1/5 phosphorylation. The concentration of circulating BMP9 was found to vary between 2 and 12 ng/mL in sera and plasma from healthy humans, a value well above its EC50 (50 pg/mL). These data indicated that BMP9 is circulating at a biologically active concentration. We then tested the effects of BMP9 in 2 in vivo angiogenic assays. We found that BMP9 strongly inhibited sprouting angiogenesis in the mouse sponge angiogenesis assay and that BMP9 could inhibit blood circulation in the chicken chorioallantoic membrane assay. Taken together, our results demonstrate that BMP9, circulating under a biologically active form, is a potent antiangiogenic factor that is likely to play a physiological role in the control of adult blood vessel quiescence.
INTRODUCTION: Understanding the multiple biological functions played by human mesenchymal stem cells (hMSCs) as well as their development as therapeutics in regenerative medicine or in cancer ...treatment are major fields of research. Indeed, it has been established that hMSCs play a central role in the pathogenesis and progression of tumours, but their impact on tumour growth remains controversial. METHODS: In this study, we investigated the influence of hMSCs on the growth of pre-established tumours. We engrafted nude mice with luciferase-positive mouse adenocarcinoma cells (TSA-Luc+) to obtain subcutaneous or lung tumours. When tumour presence was confirmed by non-invasive bioluminescence imaging, hMSCs were injected into the periphery of the SC tumours or delivered by systemic intravenous injection in mice bearing either SC tumours or lung metastasis. RESULTS: Regardless of the tumour model and mode of hMSC injection, hMSC administration was always associated with decreased tumour growth due to an inhibition of tumour cell proliferation, likely resulting from deep modifications of the tumour angiogenesis. Indeed, we established that although hMSCs can induce the formation of new blood vessels in a non-tumoural cellulose sponge model in mice, they do not modify the overall amount of haemoglobin delivered into the SC tumours or lung metastasis. We observed that these tumour vessels were reduced in number but were longer. CONCLUSIONS: Our results suggest that hMSCs injection decreased solid tumour growth in mice and modified tumour vasculature, which confirms hMSCs could be interesting to use for the treatment of pre-established tumours.
Endocrine gland-derived vascular endothelial growth factor (EG-VEGF) and its homolog Bombina variegata (Bv8), also termed prokineticin-1 and -2 (PK1 and PK2) respectively, are newly identified ...peptides with specific mitogenic activity on endocrine gland-derived endothelial cells. In the present study, we analyzed the sites of expression of EG-VEGF/PK1, Bv8/PK2, and their receptors (PKR1 and PKR2) in the adrenal cortex and checked for new biological functions of these factors on the endocrine cell compartment. RT-PCR and immunostaining analyses revealed that glomerulosa and fasciculata cells express both factors and both receptors. EG-VEGF/PK1 had no effect on the steroidogenic activity of both bovine glomerulosa and fasciculata cells but appeared to be mitogenic for both cell types. Binding of EG-VEGF/PK1 to fasciculata cells stimulated the phosphorylation of ERK1/2. Pretreatment with pertussis toxin suppressed this effect, indicating that it was Gi mediated. EG-VEGF/PK1 also increased the phosphorylation of Akt in endocrine cells of the adrenal cortex. EG-VEGF/PK1 and Bv8/PK2 thus represent new regulatory peptides acting as autocrine mitogens for endocrine cells.
Cardiac dysfunction with progressive fibrosis is a hallmark of Chagas disease. To evaluate the involvement of transforming growth factor (TGF)–β1 in this disease, TGF-β1 levels in patients were ...measured at 3 stages: asymptomatic indeterminate (IND), cardiac with no or slight heart dysfunction (Card 1), and cardiac with moderate or severe heart dysfunction (Card 2). All patients had significantly higher circulating levels of TGF-β1 than did healthy persons, and 27% of patients in the Card 1 group had higher TGF-β1 levels than did patients in the IND group. Immunohistochemical analysis of cardiac biopsy specimens showed strong fibronectin staining in the extracellular matrix and staining for phosphorylated Smad 2 (activation of the TGF-β1 signaling pathway) in cell nuclei. The higher levels of latent TGF-β1 observed in patients with myocardiopathy, together with intracellular activation of the TGF-β1 pathway and tissue fibrosis, suggest that TGF-β1 plays an important role in Chagas disease. TGF-β1 may represent a new target for preventive and curative treatments of Chagas disease
Vascular endothelial growth factor-A (VEGF-A) is highly subjected to alternative pre-mRNA splicing that generates several splice variants. The VEGF.sub.xxx and VEGF.sub.xxxb families encode splice ...variants of VEGF-A that differ only at the level of six amino acids in their C-terminal part. The expression level of VEGF.sub.xxx splice variants and their function as pro-angiogenic factors during tumor neo-angiogenesis have been well-described. The role of VEGF.sub.xxxb isoforms is less well known, but they have been shown to inhibit VEGF.sub.xxx-mediated angiogenesis, while being partial or weak activators of VEGFR receptors in endothelial cells. On the opposite, their role on tumor cells expressing VEGFRs at their surface remains largely unknown. In this study, we find elevated levels of VEGF.sub.165b, the main VEGF.sub.xxxb isoform, in 36% of non-small cell lung carcinoma (NSCLC), mainly lung adenocarcinoma (46%), and show that a high VEGF.sub.165b/VEGF.sub.165 ratio correlates with the presence of lymph node metastases. At the molecular level, we demonstrate that VEGF.sub.165b stimulates proliferation and invasiveness of two lung tumor cell lines through a VEGFR/beta1 integrin loop. We further provide evidence that the isoform-specific knockdown of VEGF.sub.165b reduces tumor growth, demonstrating a tumor-promoting autocrine role for VEGF.sub.165b in lung cancer cells. Importantly, we show that bevacizumab, an anti-angiogenic compound used for the treatment of lung adenocarcinoma patients, increases the expression of VEGF.sub.165b and activates the invasive VEGFR/beta1 integrin loop. Overall, these data highlight an unexpected role of the VEGF.sub.165b splice variant in the progression of lung tumors and their response to anti-angiogenic therapies.
Vascular endothelial growth factor-A (VEGF-A) is highly subjected to alternative pre-mRNA splicing that generates several splice variants. The VEGFxxx and VEGFxxxb families encode splice variants of ...VEGF-A that differ only at the level of six amino acids in their C-terminal part. The expression level of VEGFxxx splice variants and their function as pro-angiogenic factors during tumor neo-angiogenesis have been well-described. The role of VEGFxxxb isoforms is less well known, but they have been shown to inhibit VEGFxxx-mediated angiogenesis, while being partial or weak activators of VEGFR receptors in endothelial cells. On the opposite, their role on tumor cells expressing VEGFRs at their surface remains largely unknown. In this study, we find elevated levels of VEGF165b, the main VEGFxxxb isoform, in 36% of non-small cell lung carcinoma (NSCLC), mainly lung adenocarcinoma (46%), and show that a high VEGF165b/VEGF165 ratio correlates with the presence of lymph node metastases. At the molecular level, we demonstrate that VEGF165b stimulates proliferation and invasiveness of two lung tumor cell lines through a VEGFR/β1 integrin loop. We further provide evidence that the isoform-specific knockdown of VEGF165b reduces tumor growth, demonstrating a tumor-promoting autocrine role for VEGF165b in lung cancer cells. Importantly, we show that bevacizumab, an anti-angiogenic compound used for the treatment of lung adenocarcinoma patients, increases the expression of VEGF165b and activates the invasive VEGFR/β1 integrin loop. Overall, these data highlight an unexpected role of the VEGF165b splice variant in the progression of lung tumors and their response to anti-angiogenic therapies.
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