Abstract 1566: A cancer-stroma-cancer interacting loop promotes peritoneal metastasis of ovarian cancer through TNFα-TGFα-EGFR
Authors: Lau Tat-San , Chan Loucia Kit-Ying , Wong Chi-Hang , Man Chi-Wai , Cheung Tak-Hong , Yim So-Fan , Lee Jacqueline Ho-Sze , Chung Tony Kwok-Hung , Kwong Joseph 
Published: July 2016

Abstract
Peritoneum is the commonest site for ovarian cancer metastasis. In peritoneum, stromal fibroblasts are the second most common cell types. In this study, we aimed to investigate the role of tumor-stromal interaction in peritoneal metastasis of ovarian cancer. Using three-dimensional (3D) organoid co-culture model, we found that the interaction between metastatic human ovarian cancer cells and normal human stromal fibroblasts promotes cancer colony formation. Using cytokine antibody array, we identified a group of cytokines are de novo produced in the 3D co-culture. Among them, transforming growth factor alpha (TGF-α) was produced anew from normal stromal fibroblasts in the 3D co-culture. In the co-culture, transcription of TGF-α in normal stromal fibroblasts is activated by tumor necrosis factor alpha (TNF-α) that derived by ovarian cancer cells. By epigenetic studies, we discovered that over-expression of TNF-α in human ovarian cancer cells is due to DNA hypomethylation and chromatin remodeling in TNF-α promoter. TGF-α is a ligand of epidermal growth factor receptor (EGFR), and we confirmed EGFR is over-expressed in a significant portion of human ovarian cancer. When applying EGFR-specific inhibitors (AG1478, Gefitini, and Erlotinib) in our 3D organoid models (3D mono-cultures and 3D co-cultures), we further found that the fibroblast-derived TGF-α promotes colony formation of metastatic ovarian cancer cells in vitro through EGFR activation. In fact, TGF-α activates Hippo/YAP signaling pathway in human ovarian cancer cells via EGFR. In addition, our in vivo experiments showed that normal stromal fibroblasts promote peritoneal metastasis of ovarian cancer through EGFR activation in a xenograft model. Finally, the TNFα-TGFα-EGFR interacting loop was detected in cancer-stroma-cancer compartments of omental metastases of ovarian cancer patients by immunohistochemistry. Based on our experimental results, we proposed a cancer-stroma-cancer interacting loop that promotes peritoneal metastasis of ovarian cancer through TNFα-TGFα-EGFR. The proposed mechanism involves: 1) TNF-α is over-expressed in human ovarian cancer cells by promoter DNA hypomethylation and chromatin remodeling; 2) the ovarian cancer cell-derived TNF-α induces de novo TGF-α production in normal human omental stromal fibroblasts; and 3) the fibroblast-derived TGF-α, in turn, promotes colony formation of metastatic ovarian cancer cells through EGFR-mediated Hippo/YAP signaling pathway. Our results thereby suggest that peritoneal metastasis in the ovarian cancer patients after cytoreductive surgery can be prevented by EGFR-targeted therapy.
Citation Format: Tat-San Lau, Loucia Kit-Ying Chan, Chi-Hang Wong, Chi-Wai Man, Tak-Hong Cheung, So-Fan Yim, Jacqueline Ho-Sze Lee, Tony Kwok-Hung Chung, Joseph Kwong. A cancer-stroma-cancer interacting loop promotes peritoneal metastasis of ovarian cancer through TNFα-TGFα-EGFR. [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 1566.