Background: The tissue microenvironment plays a major role in tumor development and recurrence. It is known that leptin secreted by cancer and adipose cells can modify the tumor stroma, which is composed of immune, fibroblast, and endothelial cells (EC). Leptin affects both normal and cancer associated fibroblasts. We have previously shown that leptin can modify EC directly via an increase of angiogenic features; which was linked to VEGFR signaling and Notch expression independent of VEGF. It is hypothesized that leptin induces a communication between fibroblast and endothelial cells via induction of Notch signaling, which may be related to exosome production.

Methods: Non-expressing Ob-R fibroblasts, and fibroblasts transfected with Ob-R plasmid, were used to investigate leptin's actions on Notch activation. Fibroblasts were challenged with leptin (0.6, 1.2, 6.2 nM) and an inhibitor of Notch signaling activation (DAPT). Fibroblast culture supernatants were added to and human umbilical vein endothelial cells (HUVEC) cultures. Notch proteins and RNA expression and molecular markers of activated fibroblasts and derived exosomes were determined via Western blot, RT-PCR, and multiplex analyses, respectively. EC angiogenic features were also determined.

Results: Our findings suggest that leptin induces fibroblast activation, which triggers the expression of Notch and the development of angiogenic features by EC.

Conclusions: A novel mechanism is proposed by which leptin promotes tumor stroma development via Notch activation and a crosstalk between fibroblasts and EC. Cancer therapies targeting leptin signaling could be a new strategy for interfering with cellular processes that promotes changes of tumor stroma towards a more aggressive tumor environment.

Citation Format: Viola Lanier. Leptin induces a fibroblast and endothelial cell crosstalk in tumor stroma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 227.