RESUMO
Angiogenesis is a coordinated process tightly regulated by the balance between Delta-like-4 (DLL4) and Jagged-1 (JAG1) in endothelial cells. Here we show that galectin-3 (gal-3), a glycan-binding protein secreted by cancer cells under hypoxic conditions, triggers sprouting angiogenesis, assisted by hypoxic changes in the glycosylation status of endothelial cells that enhance binding to gal-3. Galectin-3's proangiogenic functions were found to be predominantly dependent on the Notch ligand JAG1. Differential direct binding to JAG1 was shown by surface plasmon resonance assay. Upon binding to Notch ligands, gal-3 preferentially increased JAG1 protein half-life over DLL4 and preferentially activated JAG1/Notch-1 signaling in endothelial cells. JAG1 overexpression in Lewis lung carcinoma cells accelerated tumor growth in vivo, but this effect was prevented in Lgals3-/- mice. Our findings establish gal-3 as a molecular regulator of the JAG1/Notch-1 signaling pathway and have direct implications for the development of strategies aimed at controlling tumor angiogenesis.
Assuntos
Galectina 3/metabolismo , Proteína Jagged-1/metabolismo , Neoplasias/metabolismo , Neoplasias/patologia , Neovascularização Patológica/metabolismo , Receptores Notch/metabolismo , Animais , Proteínas Sanguíneas , Modelos Animais de Doenças , Células Endoteliais/metabolismo , Galectina 3/genética , Galectinas , Humanos , Hipóxia/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Ligantes , Proteínas de Membrana/metabolismo , Camundongos , Camundongos Knockout , Modelos Biológicos , Neoplasias/genética , Neovascularização Patológica/genética , Ligação Proteica , Transdução de SinaisRESUMO
OBJECTIVE: To investigate the use of the National Cancer Institute's hollow fiber assay (HFA) to evaluate and prioritize novel treatment strategies for clinical trials in the Ewing's sarcoma family of tumors (ESFT). STUDY DESIGN: The growth and morphology of ESFT cell lines in hollow fibers (HFs) was characterized in vitro and in vivo. Reliability and reproducibility were evaluated using doxorubicin. RESULTS: The numbers of viable cells in all 6 ESFT cell lines increased with time in vitro (0 to 96 hours). The SKES-1 and A673 cell lines grew exponentially after implantation of HFs in nude mice at subcutaneous and intraperitoneal sites. ESFT cells formed highly organized distinctive morphology within the HFs in vitro and in vivo. The number of viable ESFT cells within the HFs decreased in a time-dependent (24 to 96 hours) and dose-dependent (1 to 10 mg/kg) manner after treatment with doxorubicin in vivo. CONCLUSIONS: The HFA is a versatile short-term in vivo model that may be exploited to predict efficacy of potential anticancer agents in ESFT cells. Tumor markers and pharmacodynamic endpoints may be quantified in the pure population of ESFT cells from within the HFs.