Normal Fibroblasts Induce E-Cadherin Loss and Increase Lymph Node Metastasis in Gastric Cancer

Background: A tumor is considered a heterogeneous complex in a three-dimensional environment that is flush with pathophysiological and biomechanical signals. Cell-stroma interactions guide the development and generation of tumors. Here, we evaluate the contributions of normal fibroblasts to gastric cancer. Methodology/Principal Findings: By coculturing normal fibroblasts in monolayers of BGC-823 gastric cancer cells, tumor cells sporadically developed short, spindle-like morphological characteristics and demonstrated enhanced proliferation and invasive potential. Furthermore, the transformed tumor cells demonstrated decreased tumor formation and increased lymphomatic and intestinal metastatic potential. Non-transformed BGC-823 cells, in contrast, demonstrated primary tumor formation and delayed intestinal and lymph node invasion. We also observed E-cadherin loss and the upregulation of vimentin expression in the transformed tumor cells, which suggested that the increase in metastasis was induced by epithelial-to-mesenchymal transition. Conclusion: Collectively, our data indicated that normal fibroblasts sufficiently induce epithelial-to-mesenchymal transition in cancer cells, thereby leading to metastasis.