The tumor microenvironment is known to play a critical role in tumor progression, invasion and metastasis. The epithelial-to-mesenchymal transition (EMT) is understood as a process of tumor invasion and metastasis. Therefore, we investigated the relation between the EMT and the microenvironment of colorectal carcinoma (CRC). The histological features and expression of EMT markers in tumor cells and surrounded stromal cells were obtained from the surgically resected tissues of 39 patients using microscopic review and immunohistochemistry. The loss of expression of E-cadherin was more prominent in the invasive front of tumor than the surface, where α-smooth muscle actin-positive carcinoma-associated fibroblasts (CAFs) are accumulated. The signaling molecules of the Wnt and TGF-β1-Smad pathway were expressed more frequently in the tumor cells and/or CAFs of the invasive margin than those of the tumor surface. The expressions of related transcription factors, such as SNAIL and ZEB1, were increased in the tumor cells and CAFs. The process of EMT may be activated in the tumor margin of CRC under the control of CAFs. Related signaling molecules and transcription factors might be induced by paracrine effects of the surrounding CAFs.
Keywords: Colorectal carcinoma; carcinoma-associated fibroblasts; epithelial-to-mesenchymal transition; microenvironment.