RESUMO
Angiogenesis is controlled by several regulatory mechanisms, including the Notch and fibroblast growth factor (FGF) signaling pathways. FGF1, a prototype member of FGF family, lacks a signal peptide and is released through an endoplasmic reticulum-Golgi-independent mechanism. A soluble extracellular domain of the Notch ligand Jagged1 (sJ1) inhibits Notch signaling and induces FGF1 release. Thrombin, a key protease of the blood coagulation cascade and a potent inducer of angiogenesis, stimulates rapid FGF1 release through a mechanism dependent on the major thrombin receptor protease-activated receptor (PAR) 1. This study demonstrates that thrombin cleaves Jagged1 in its extracellular domain. The sJ1 form produced as a result of thrombin cleavage inhibits Notch-mediated CBF1/Suppressor of Hairless [(Su(H)]/Lag-1-dependent transcription and induces FGF1 expression and release. The overexpression of Jagged1 in PAR1 null cells results in a rapid thrombin-induced export of FGF1. These data demonstrate the existence of novel cross-talk between thrombin, FGF, and Notch signaling pathways, which play important roles in vascular formation and remodeling.
Assuntos
Proteínas de Ligação ao Cálcio/metabolismo , Fármacos Cardiovasculares/metabolismo , Fator 1 de Crescimento de Fibroblastos/metabolismo , Peptídeos e Proteínas de Sinalização Intercelular/metabolismo , Proteínas de Membrana/metabolismo , Fragmentos de Peptídeos/metabolismo , Trombina/farmacologia , Animais , Proteínas de Ligação ao Cálcio/química , Linhagem Celular , Células Endoteliais/efeitos dos fármacos , Células Endoteliais/metabolismo , Fator 1 de Crescimento de Fibroblastos/genética , Humanos , Peptídeos e Proteínas de Sinalização Intercelular/química , Proteína Jagged-1 , Proteínas de Membrana/química , Camundongos , Peso Molecular , Células-Tronco Multipotentes/citologia , Células-Tronco Multipotentes/efeitos dos fármacos , Células-Tronco Multipotentes/metabolismo , Crista Neural/citologia , Estrutura Terciária de Proteína , Transporte Proteico/efeitos dos fármacos , Receptor PAR-1/metabolismo , Receptores de Fatores de Crescimento de Fibroblastos/metabolismo , Receptores Notch/metabolismo , Receptores de Trombina , Proteínas Serrate-Jagged , Transdução de Sinais/efeitos dos fármacos , Transcrição Gênica/efeitos dos fármacosRESUMO
Notch functions as an oncogene or tumor inhibitor in various cancers, and decreases in Notch2 expression are associated with increasing grade of human breast cancer. We constitutively activated Notch signaling with intracellular domain (ICD) expression in the human adenocarcinoma line MDA-MB-231. Notch2 signaling increased apoptosis, whereas Notch4ICD (int3) significantly increased cell proliferation and growth. Cells with activated Notch2 or Notch4 were injected into nu/nu mice for analysis of in vivo tumor xenograft phenotype. Tumor growth was significantly altered depending on the receptor activated. Notch2ICD potently suppressed tumor take and growth, leading to a 60% decrease in tumors and significantly smaller, necrotic tumors. Despite this, Notch2ICD tumors were highly vascularized, although the vessels were smaller and comprised a more immature network compared with Notch4ICD tumors. Notch4ICD tumors were highly aggressive and well vascularized, indicating a role for Notch4 signaling in the promotion of the malignant phenotype in addition to its transforming ability. Although both NotchICD groups expressed angiogenic factors, Notch4ICD had selective vascular endothelial growth factor-D in both tumor and host stroma, suggesting a differential regulation of cytokines that may impact vascular recruitment and autocrine tumor signaling. Our results demonstrate that Notch2 signaling is a potent inhibitory signal in human breast cancer xenografts.