The Notch ligand delta-like 3 promotes tumor growth and inhibits Notch signaling in lung cancer cells in mice.

Although it has been suggested that Dll3, one of the Notch ligands, promotes the proliferation and inhibits the apoptosis of cancer cells, the role of Dll3 in cancers remains unclear. In this study, we found that in the murine Lewis lung carcinoma (LLC) cells, the level of Dll3 mRNA changed upon tumor microenvironment (TME) stimulation, namely, decreased under hypoxia or stimulated with tumor necrosis factor (TNF)-α. Dll3 was also expressed at higher level in human lung carcinoma tissues than in the para-carcinoma tissues. Overexpression of Dll3 in LLC cells promoted cell proliferation and reduced apoptosis in vitro, and enhanced tumor growth when inoculated in vivo in mice. The Dll3-mediated proliferation could be due to increased Akt phosphorylation in LLC cells, because an Akt inhibitor counteracted Dll3-induced proliferation. Moreover, Dll3 overexpression promoted PI3K/Akt signaling through inhibiting Notch signaling.

miR-342-5p Is a Notch Downstream Molecule and Regulates Multiple Angiogenic Pathways Including Notch, Vascular Endothelial Growth Factor and Transforming Growth Factor ß Signaling.

BACKGROUND: Endothelial cells (ECs) form blood vessels through angiogenesis that is regulated by coordination of vascular endothelial growth factor (VEGF), Notch, transforming growth factor ß, and other signals, but the detailed molecular mechanisms remain unclear. METHODS AND RESULTS: Small RNA sequencing initially identified miR-342-5p as a novel downstream molecule of Notch signaling in ECs. Reporter assay, quantitative reverse transcription polymerase chain reaction and Western blot analysis indicated that miR-342-5p targeted endoglin and modulated transforming growth factor ß signaling by repressing SMAD1/5 phosphorylation in ECs. Transfection of miR-342-5p inhibited EC proliferation and lumen formation and reduced angiogenesis in vitro and in vivo, as assayed by using a fibrin beads-based sprouting assay, mouse aortic ring culture, and intravitreal injection of miR-342-5p agomir in P3 pups. Moreover, miR-342-5p promoted the migration of ECs, accompanied by reduced endothelial markers and increased mesenchymal markers, indicative of increased endothelial-mesenchymal transition. Transfection of endoglin at least partially reversed endothelial-mesenchymal transition induced by miR-342-5p. The expression of miR-342-5p was upregulated by transforming growth factor ß, and inhibition of miR-342-5p attenuated the inhibitory effects of transforming growth factor ß on lumen formation and sprouting by ECs. In addition, VEGF repressed miR-342-5p expression, and transfection of miR-342-5p repressed VEGFR2 and VEGFR3 expression and VEGF-triggered Akt phosphorylation in ECs. miR-342-5p repressed angiogenesis in a laser-induced choroidal neovascularization model in mice, highlighting its clinical potential. CONCLUSIONS: miR-342-5p acts as a multifunctional angiogenic repressor mediating the effects and interaction among angiogenic pathways.