Endothelial Dll4 overexpression reduces vascular response and inhibits tumor growth and metastasization in vivo

This work was supported by the Portuguese Foundation for Science and Technology (FCT; http://www.fct.pt/index.phtml.en), Project PTDC/CVT/115703/2009 to AD; PTDC/SAU-ONC/116164/2009 and PTDC/SAU-ONC/121742/2010 to AT. DD, JG and LM are PhD students supported by grants SFRH/BD/29447/2006, SFRH/BD/73264/2010 and SFRH/BD/74229/2010 from FCT. AT is a Postdoctoral Researcher supported by grants SFRH/BPD/47079/2008 and SFRH/BPD/110174/2015 from FCT. CIISA has provided support through Project UID/CVT/00276/2013, funded by FCT. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. EditorBackground: The inhibition of Delta-like 4 (Dll4)/Notch signaling has been shown to result in excessive, nonfunctional vessel proliferation and significant tumor growth suppression. However, safety concerns emerged with the identification of side effects resulting from chronic Dll4/Notch blockade. Alternatively, we explored the endothelial Dll4 overexpression using different mouse tumor models. Methods: We used a transgenic mouse model of endothelial-specific Dll4 overexpression, previously produced. Growth kinetics and vascular histopathology of several types of solid tumors was evaluated, namely Lewis Lung Carcinoma xenografts, chemically-induced skin papillomas and RIP1-Tag2 insulinomas. Results: We found that increased Dll4/Notch signaling reduces tumor growth by reducing vascular endothelial growth factor (VEGF)-induced endothelial proliferation, tumor vessel density and overall tumor blood supply. In addition, Dll4 overexpression consistently improved tumor vascular maturation and functionality, as indicated by increased vessel calibers, enhanced mural cell recruitment and increased network perfusion. Importantly, the tumor vessel normalization is not more effective than restricted vessel proliferation, but was found to prevent metastasis formation and allow for increased delivery to the tumor of concomitant chemotherapy, improving its efficacy. Conclusions: By reducing endothelial sensitivity to VEGF, these results imply that Dll4/Notch stimulation in tumor microenvironment could be beneficial to solid cancer patient treatment by reducing primary tumor size, improving tumor drug delivery and reducing metastization. Endothelial specific Dll4 overexpression thus appears as a promising anti-angiogenic modality that might improve cancer control. © 2017 The Author(s).publishersversionpublishe