Background & Aims: Esophageal squamous cell carcinoma (ESCC) is known to be a highly angiogenic tumor. Here, we investigated the role of the stromal fibroblasts in the ESCC-induced angiogenic response using a novel 3-dimensional model. Methods: A novel assay was developed where cocultures of ESCC and esophageal fibroblasts induced human microvascular endothelial cell (HMVEC) vascular network formation in a 3-dimensional collagen gel. Biochemical studies showed that the ESCC-induced activation of the fibroblasts was required to induce vascular network formation via a transforming growth factor (TGF)-β and vascular endothelial growth factor (VEGF)-dependent pathway. Results: Conditioned media from a panel of 4 ESCC lines transdifferentiated normal esophageal fibroblasts into myofibroblasts via TGF-β signaling. The presence of fibroblasts was essential for efficient HMVEC network formation, and the addition of ESCC cells to these cultures greatly enhanced the angiogenic process. The role of TGF-β in this process was shown by the complete inhibition of network formation following TGF-β inhibitor treatment. Finally, we showed that ESCC-derived TGF-β regulates angiogenesis through the release of VEGF from the fibroblasts and that the VEGF release was blocked following TGF-β inhibition. Conclusions: This study shows the essential role of fibroblasts in the ESCC angiogenic-induced response and suggests that the pharmacologic targeting of the TGF-β signaling axis could be of therapeutic benefit in this deadly disease.
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