Rabbit Anti-JAG1 monoclonal antibody, clone KG07-17

Rare inherited cardiovascular diseases are frequently caused by mutations in genes that are essential for the formation and/ or function of the cardiovasculature. Hereditary Haemorrhagic Telangiectasia is a familial disease of this type. The majority of patients carry mutations in either Endoglin (ENG) or ACVRL1 (also known as ALK1) genes, and the disease is characterized by arteriovenous malformations and persistent haemorrhage. ENG and ACVRL1 encode receptors for the TGF beta superfamily of ligands, that are essential for angiogenesis in early development but their roles are not fully understood. Our goal was to examine the role of Acvrl1 in vascular endothelial cells during vascular development and to determine whether loss of endothelial Acvrl1 leads to arteriovenous malformations. Acvrl1 was depleted in endothelial cells either in early postnatal life or in adult mice. Using the neonatal retinal plexus to examine angiogenesis, we observed that loss of endothelial Acvrl1 led to venous enlargement, vascular hyperbranching and arteriovenous malformations. These phenotypes were associated with loss of arterial Jag1 expression, decreased pSmad1/5/8 activity and increased endothelial cell proliferation. We found that Endoglin was markedly down-regulated in Acvrl1-depleted ECs showing endoglin expression to be downstream of Acvrl1 signalling in vivo. Endothelial-specific depletion of Acvrl1 in pups also led to pulmonary haemorrhage, but in adult mice resulted in caecal haemorrhage and fatal anaemia. We conclude that during development, endothelial Acvrl1 plays an essential role to regulate endothelial cell proliferation and arterial identity during angiogenesis, whilst in adult life endothelial Acvrl1 is required to maintain vascular integrity.

Purpose: Although the existence of cancer stem cells (CSC) in adenoid cystic carcinoma (ACC) has been proposed, lack of assays for their propagation and uncertainty about molecular markers prevented their characterization. Our objective was to isolate CSC from ACC and provide insight into signaling pathways that support their propagation. Experimental Design: To isolate CSC from ACC and characterize them, we used ROCK inhibitor-supplemented cell culture, immunomagnetic cell sorting, and in vitro/in vivo assays for CSC viability and tumorigenicity. Results: We identified in ACC CD133-positive CSC that expressed NOTCH1 and SOX10, formed spheroids, and initiated tumors in nude mice. CD133(+) ACC cells produced activated NOTCH1 (N1ICD) and generated CD133(+) cells that expressed JAG1 as well as neural differentiation factors NR2F1, NR2F2, and p27Kip1. Knockdowns of NOTCH1, SOX10, and their common effector FABP7 had negative effects on each other, inhibited spheroidogenesis, and induced cell death pointing at their essential roles in CSC maintenance. Downstream effects of FABP7 knockdown included suppression of a broad spectrum of genes involved in proliferation, ribosome biogenesis, and metabolism. Among proliferation-linked NOTCH1/FABP7 targets, we identified SKP2 and its substrate p27Kip1. A gamma-secretase inhibitor, DAPT, selectively depleted CD133(+) cells, suppressed N1ICD and SKP2, induced p27Kip1, inhibited ACC growth in vivo, and sensitized CD133(+) cells to radiation. Conclusions: These results establish in the majority of ACC the presence of a previously uncharacterized population of CD133(+) cells with neural stem properties, which are driven by SOX10, NOTCH1, and FABP7. Sensitivity of these cells to Notch inhibition and their dependence on SKP2 offer new opportunities for targeted ACC therapies. (C) 2016 AACR.