YKL-40 regulated epithelial-mesenchymal transition and migration/invasion enhancement in non-small cell lung cancer

Background: YKL-40 is a secreted inflammatory protein that its overexpression has been reported to correlate with poor outcome of various malignant diseases, especially in cancer. However, the function of this protein is still unclear. Methods: The clinical prognosis of non-small cell lung cancers (NSCLC) patients and their clinical YKL-40 expressions were obtained from the Prognoscan database. The expressions of YKL-40 in patient samples were determined by Western Blotting assay. YKL-40 gene knockdown and overexpression were performed on NSCLC cancer cells (CL1-1 and CL1-5). The cells were investigated for their epithelial-mesenchymal transition (EMT) markers gene modulation through Western Blotting and RT-PCR. Further cell metastatic abilities were assessed by transwell migration and invasion assay. Result: In this study, YKL-40 was observed to be highly expressed in NSCLC specimens. Furthermore, determined by the PrognoScan database analysis, patients with high expression levels of YKL-40 were found with poor prognosis. In the in vitro study, different characteristics of NSCLC cell lines (CL1-1, H23, H838, CL1-5, and H2009) were used as study models, where YKL-40 expression levels were determined to correlate with the phenotypic characteristics of cancer metastasis. In this study, YKL-40 was demonstrated to regulate EMT marker expressions such as Twist, Snail, Slug, N-cadherin, Vimentin, and E-cadherin. The protein's affects in cancer cell migration and invasion were also observed in YKL-40 overexpression or knock down NSCLC cell lines. Conclusion: All of results from this study suggest that YKL-40 is a major factor in NSCLC metastasis. Thus, YKL-40 may serve as therapeutic target for NSCLC patients in the future.