Chemokine (C-C motif) ligand 21/C-C chemokine receptor type 7 triggers migration and invasion of human lung cancer cells by epithelial-mesenchymal transition via the extracellular signal-regulated kinase signaling pathway

C-C chemokine receptor type 7 (CCR7) has been implicated in lymph node metastasis of various cancers. Previous studies have revealed that epithelial-mesenchymal transition (EMT) is involved in the chemotactic process mediated by CCR7 and its ligands in various types of carcinoma. However, the underlying mechanism of this process remains to be fully elucidated. The present study investigated whether chemokine (C-C motif) ligand 21 (CCL21)/CCR7 may activate EMT of lung cancer cells and their associated signaling pathways. A549 and H520 lung cancer cell lines were examined in vitro in the present study. The results indicated that A549 and H520 expressed CCR7, but reduced levels of CCL21. Following stimulation of lung cancer cell lines with CCL21, the expression of the epithelial marker E-cadherin was downregulated, and the mesenchymal markers Vimentin/Slug and extracellular signal-regulated kinase (ERK) were upregulated. In addition, the ERK inhibitor PD98059 may inhibit EMT caused by CCL21, and decreased cell migration and invasion initiated by CCL21. Furthermore, lung adenocarcinoma tissues from 50 patients who underwent lung cancer operations were investigated by immunohistochemistry. The findings revealed that CCR7, Slug and Vimentin were highly expressed in lung carcinoma tissues, and were significantly associated with lymph node metastasis and clinical pathological stages, respectively. CCR7 expression was correlated positively with expression levels of Slug and Vimentin. CCL21 was expressed positively in the endothelium of lymphatic vessels adjacent to cancer cells, and weakly in lung cancer cells. Collectively, these results demonstrated that CCL21/CCR7 may activate EMT in lung cancer cells via the ERK1/2 signaling pathway. The current study provides evidence that a close interaction exists between CCL21/CCR7chemotaxis and EMT procedures in lung cancer metastasis, providing a basis for the development of therapeutic targets.