Cancer-associated fibroblasts induce epithelial-mesenchymal transition through secreted cytokines in endometrial cancer cells

Endometrial cancer (EC) is the most common malignant gynecological disease. Cancer-associated fibroblasts (CAFs) serve an important role in the development and progression of EC through epithelial-mesenchymal transition (EMT). The aim of the present study was to examine the association between CAFs and EMT, and the possible mechanisms of action. Firstly, the CAFs and normal fibroblasts (NFs) were isolated and cultured, then an immunofluorescence assay was performed to analyze the purity and level of activation of CAFs and NFs, and then the conditional medium (CM) of CAFs and NFs was prepared. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) and western blotting examined the expression levels of epithelial (E)-cadherin, neural (N)-cadherin and vimentin. A Matrigel(®) invasion assay and wound healing assay were used to analyze the effect of the CM on invasion and migration. An ELISA assay also measured the levels of various cytokines in the CM. In addition, EMT-associated proteins in metastatic lung tissues were detected by immunohistochemical assay. The results indicated that the CM of CAFs may decrease the level of E-cadherin, and increase the levels of N-cadherin and vimentin, while increasing the levels of invasion and metastasis in EC cells. The concentration of epidermal growth factor, transforming growth factor-β, hepatic growth factor and fibroblast growth factor in the CM of CAFs increased significantly, in comparison with the NFs group (P<0.05). The exogenous growth factors induced migration and invasion of EC cells. CAFs induced lung metastasis and the EMT process in vivo. These data suggested that cancer-associated fibroblasts may induce EMT through the secreted cytokines in endometrial cancer cells.