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Articles by P Angel
Total Records ( 2 ) for P Angel
  W Lederle , B Hartenstein , A Meides , H Kunzelmann , Z Werb , P Angel and M. M. Mueller

Matrix metalloproteinases (MMPs) such as MMP13 promote tumour growth and progression by mediating extracellular matrix (ECM) reorganization and regulating the biological activity of cytokines. Using Mmp13–/– mice, we demonstrate an essential role of this single collagenase for highly malignant and invasive growth in skin squamous cell carcinoma (SCC). Lack of host MMP13 strongly impaired tumour growth of malignant SCC cells, leading to small, mostly avascular cysts. While initial stromal activation in tumour transplants of Mmp13+/+ and Mmp13–/– animals was similar, MMP13 was essential for maintenance of angiogenesis and for invasion. MMP13 was induced in fibroblasts of the wild-type animals at the onset of invasion and correlated with a strong increase in vascular endothelial growth factor (VEGF) protein and its association with vascular endothelial growth factor receptor-2 on endothelial cells in invasive areas. In contrast, VEGF protein in the stroma was barely detectable and tumour invasion was downregulated in Mmp13–/– animals, despite ongoing VEGF messenger RNA expression. Taken together with in vitro data showing the release of VEGF from the ECM by MMP13 expressing fibroblasts, these data strongly suggest a crucial role of MMP13 in promoting angiogenesis via releasing VEGF from the ECM and thus allowing the invasive growth of the SCC cells.

  B Hu , K Lefort , W Qiu , B. C Nguyen , R. D Rajaram , E Castillo , F He , Y Chen , P Angel , C Brisken and G. P. Dotto

Epithelial–mesenchymal interactions are key to skin morphogenesis and homeostasis. We report that maintenance of the hair follicle keratinocyte cell fate is defective in mice with mesenchymal deletion of the CSL/RBP-J gene, the effector of "canonical" Notch signaling. Hair follicle reconstitution assays demonstrate that this can be attributed to an intrinsic defect of dermal papilla cells. Similar consequences on hair follicle differentiation result from deletion of Wnt5a, a specific dermal papilla signature gene that we found to be under direct Notch/CSL control in these cells. Functional rescue experiments establish Wnt5a as an essential downstream mediator of Notch–CSL signaling, impinging on expression in the keratinocyte compartment of FoxN1, a gene with a key hair follicle regulatory function. Thus, Notch/CSL signaling plays a unique function in control of hair follicle differentiation by the underlying mesenchyme, with Wnt5a signaling and FoxN1 as mediators.

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