Lymphangiogenesis in the uterine horns: Implication of the Netrin-1 and UNC5B signaling pathway in physiology and cancer

The lymphatic system consists of an open, unidirectional network of lymphatic vessels maintaining tissue homeostasis, intestinal absorption, immunosurveillance and immunomodulation. These vessels are lined by lymphatic endothelial cells (LECs). Lymphangiogenesis, defined as sprouting of new lymphatic vessels from pre-existing vessels or embryonic veins, is the main mechanism driving the formation and expansion of lymphatic networks during embryogenesis and in adults under physiological conditions. This process involves numerous molecules, most notably VEGF-C, but also axon-guidance cues such as Netrins (Hu et al., 2024). Lymphangiogenesis shares many features with angiogenesis, which depends mainly on VEGF-A, but also Netrin-1. Netrin-1, acting through its receptor UNC5B, regulates vascular endothelial migration and branching, thereby stabilizing the vascular network (Lu et al., 2004). In our laboratory, scRNAseq analysis of murine uterine horns revealed that Netrin-1 and UNC5B are specifically expressed by LECs. The lymphatic network of uterine horns has never been investigated, nor has the role of the Netrin-1 and UNC5B in lymphangiogenesis in general. We hypothesize that Netrin-1 and UNC5B contributes to lymphatic network development by regulating LEC migration and tubulogenesis. Our preliminary in vivo data describe the expression patterns of Netrin-1 and UNC5B during lymphatic development in murine uterine horns. UNC5B and Netrin-1 knockout models are being generated to define their functional roles. In vitro studies on human dermal LECs are assessing Netrin-1 effects on migration and tubulogenesis. The lymphatic system is a key route for metastatic dissemination, notably in endometrial cancer (Donoghue et al., 2007). Uterine horns are continuously lined by the endometrium, suggesting that lymphatic vessels within uterine horns may provide a pathway for endometrial cancer cell dissemination. Although Netrin-1 is normally absent in adult tissues, it is re-expressed in tumors, where it promotes tumor progression. If Netrin-1 contributes to lymphangiogenesis in uterine horns, it may similarly modulate lymphatic vessel formation and thereby facilitate metastasis in endometrial cancer. Consistent with this, preliminary results showed that the neutralizing antibody anti-Netrin-1 in mice grafted with endometrial cancer cells significantly reduces lung metastases. The knockout models will help define how Netrin-1 and UNC5B could regulate lymphatic-dependent metastatic spread. This project aims to characterize lymphangiogenesis in uterine horns and to define the roles of Netrin-1 and UNC5B in physiological and tumor contexts. Ultimately, this work may support new therapeutic applications for the anti-Netrin-1 antibody developed in our laboratory, currently in phase II clinical trial.