Abstract LB-367: Wnt-dependent transcription factor LEF-1 controls endothelial cell invasion through changes of MMP-2 expression

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC Background: Wnt signaling is involved in many events including embryogenesis, stem cell regulation, morphogenesis, cell fate determination, and oncogenesis. The role of Wnt pathway in angiogenesis is proposed, however the mechanism is still unclear. Most cancers express elevated levels of different Wnts when compared to normal cells. LEF-1 is a participant in and a target gene of the Wnt/ -catenin pathway. LEF-1 increases the in vitro invasiveness of cancer cells. Hypothesis: We suggest that LEF-1 controls the invasion also in endothelial cells. We hypothesize further that cancer affects local tumor angiogenesis via Wnt pathway-dependent up-regulation of LEF-1 in endothelial cells (EC). Methods: To test this hypothesis we construct a model system: endothelial cell line EaHy926 treated with Wnt3a (mostly known as a canonical Wnt signal) conditioned medium or grown in co-culture with L-cells producing Wnt3a. Results: Wnt3a increases nuclear s-catenin in human endothelial cell line, and up-regulates LEF/TCF-dependent promoter activity. Wnt3a augments its target gene's LEF-1 promoter activity and LEF-1 mRNA concentration, demonstrating involvement of some transcription factors with E-tails. Both Wnt3a treatment and LEF-1 overexpression elevate MMP-2 mRNA level. Elimination of Wnt-dependent induction of MMP-2 gene expression by LEF-1 siRNA confirms the LEF-1 role in the MMP-2 control mechanism. Loosening up the extracellular matrix MMPs allows the cells to move around. These enzymes are integral part of invasion process. Indeed, LEF-1 up-regulates endothelial cells invasiveness in Matrigel matrix. LEF-1 increases also EC proliferation, in agreement with published data for parental primary endothelial culture HUVEC. Conclusions: In endothelial cells canonical (s-catenin) Wnt signaling enhances invasiveness of EC via LEF-1 - dependent regulation of MMP-2 expression. There is a number of similarities between primary cells HUVEC, studied by others, and cell line EAhy926 in their response to Wnt3a. This indicates that EAhy926 cell line conserves many components of angiogenesis control by Wnt/β-catenin pathway and could serve as a simplified model to study this regulation, replacing primary endothelial cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-367.