Ets family members induce lymphangiogenesis through physical and functional interaction with Prox1

Abstract

SummaryProx1 plays pivotal roles during embryonic lymphatic development and maintenance of adult lymphatic systems by modulating the expression of various lymphatic endothelial cell (LEC) markers, such as vascular endothelial growth factor receptor 3 (VEGFR3). However, the molecular mechanisms by which Prox1 transactivates its target genes remain largely unknown. Here, we identified Ets-2 as a candidate molecule that regulates the functions of Prox1. Whereas Ets-2 has been implicated in angiogenesis, its roles during lymphangiogenesis have not yet been elucidated. We found that endogenous Ets-2 interacts with Prox1 in LECs. Using an in vivo model of chronic aseptic peritonitis, we found that Ets-2 enhanced inflammatory lymphangiogenesis, whereas a dominant-negative mutant of Ets-1 suppressed it. Ets-2 also enhanced endothelial migration towards VEGF-C through induction of expression of VEGFR3 in collaboration with Prox1. Furthermore, we found that both Prox1 and Ets-2 bind to the VEGFR3 promoter in intact chromatin. These findings suggest that Ets family members function as transcriptional cofactors that enhance Prox1-induced lymphangiogenesis.

Interaction of tumor cells and lymphatic vessels in cancer progression

“…4 During early steps of lymphatic endothelial cell specification, Ets-family transcription factors are also abundantly expressed in blood vascular endothelial cells and, when co-expressed with Prox-1, enhance the transcriptional activator activities of Prox-1. 5 Prox-1, with or without Ets and the later expressed transcription factor COUP-TFII, upregulates the expression of further lymphangiogenic signaling molecules such as vascular endothelial growth factor receptor 3 (VEGFR-3) and integrin a9. Lymphatic endothelial progenitor cells expressing Prox-1 migrate from the cardinal veins into the adjacent mesenchyme, where they form the primary lymphatic plexus.…”

Bone morphogenetic protein-9 inhibits lymphatic vessel formation via activin receptor-like kinase 1 during development and cancer progression

“…We used a mouse model of chronic aseptic peritonitis to examine whether BMP-9 inhibits inflammatory lymphangiogenesis (30). To examine the effects of BMP-9, adenoviruses (Ad) encoding lacZ (control) and BMP9 were intraperitoneally administered with thioglycollate medium (a proinflammatory agent) to immune-competent BALB/c mice.…”

Ets-1 Is Required for the Activation of VEGFR3 during Latent Kaposi's Sarcoma-Associated Herpesvirus Infection of Endothelial Cells

“…KSHV also induces Prox-1 in blood endothelial cells, and therefore, Prox-1 and Ets-1 could synergize to induce the VEGFR3 promoter in KSHV-infected cells to achieve optimal VEGFR3 expression. This was reported to be the case in human umbilical vein endothelial cells (HUVEC) (66). However, in TIME cells or HEK293 cells, Prox-1 did not synergistically increase VEGFR3 promoter activation by Ets-1 (data not shown).…”

“…Interestingly, podoplanin, another lymphatic endothelial cell-specific gene, is highly induced by KSHV, even when Ets-1 is blocked, indicating that Ets-1 is specific to VEGFR3 and is not involved in overall lymphatic reprogramming. A previous study in macrovascular endothelial cells showed that Prox-1 acts synergistically with Ets-2 to induce lymphangiogenesis and that Ets-2, and to a much lesser extent Ets-1, can bind to Prox-1 and potentiate its activation of VEGFR3 (66). We found that Ets-1 activates the promoter of VEGFR3 in the absence of Prox-1 expression in endothelial cells, as well as in nonendothelial cells; however, relatively little is known about the regulation of the VEGFR3 promoter.…”