YBX1 regulates tumor growth via CDC25a pathway in human lung adenocarcinoma
Wei Guo，Chundong Gu
Y-box binding protein 1 (YBX1) is involved in the multi-tumor occurrence and development. However, the regulation of YBX1 in lung tumorigenesis and the underlying mechanisms, especially its relationship with CDC25a, was remains unclear. In this study, we analyzed the expression and clinical significance of YBX1 and CDC25a in lung adenocarcinoma and identified their roles in the regulation of lung cancer growth. The retrospective analysis of 116 patients with lung adenocarcinoma indicated that YBX1 was positively correlated with CDC25a expression. The Cox-regression analysis showed only high-ranking TNM stage and low CDC25a expression were an independent risk factor of prognosis in enrolled patients. High expression of YBX1 or CDC25a protein was also observed in lung adenocarcinoma cells compared with HLF cells. ChIP assay demonstrated the binding of endogenous YBX1 to the CDC25a promoter region. Overexpression of exogenous YBX1 up-regulated the expression of the CDC25a promoter-driven luciferase. By contrast, inhibition of YBX1 by siRNA markedly decreased the capability of YBX1 binding to CDC25a promoter in A549 and H322 cells. Inhibition of YBX1 expression also blocked cell cycle progression, suppressed cell proliferation and induced apoptosis via the CDC25a pathway in vitro. Moreover, inhibition of YBX1 by siRNA suppressed tumorigenesis in a xenograft mouse model and down-regulated the expression of YBX1, CDC25a, Ki67 and cleaved caspase 3 in the tumor tissues of mice. Collectively, these results demonstrate inhibition of YBX1 suppressed lung cancer growth partly via the CDC25a pathway and high expression of YBX1/CDC25a predicts poor prognosis in human lung adenocarcinoma.We analyzed the expression of YBX1 and CDC25a in 116 patients with complete surgical resection of lung adenocarcinoma by IHC staining. Among the total patients, 56 (48.3%) patients had CDC25a high expression which predominantly located in nucleus and a small portion in cytoplasm. Meanwhile, 43 (37.1%) patients had YBX1 high expression which was usually seen in cytoplasm and a little in nucleus or extracellular matrix (Figure
1). More interestingly, the patients with MIA, a less aggressive subtype of adenocarcinoma, had neither YBX1 nor CDC25a high expression in accordance with IASLC/ATS/ERS international multidisciplinary classification. Similarly, the higher pathological component risk rating, the more proportion of YBX1 and CDC25a expression in tumor lesions. Subsequently, we explored the expression and location of YBX1 and CDC25a in vitro by immunofluorescence assay (Figure
2A). YBX1 was mainly presented in cytoplasm of human lung adenocarcinoma cell lines (A549, H322 and Hcc827) but little in normal human embryonic lung fibroblasts cell line (HLF). Moreover, A549, H322 and Hcc827 cells had obvious YBX1 nuclear translocation compared with HLF cells. CDC25a was also found to be highly expressed in nucleus of A549, H322 and Hcc827 cells. The same result was confirmed using the total, nuclei and cytoplasm proteins extracted from HLF, A549, H322 and Hcc827 cells by Western blot analysis (Figure 2B–2D).Three human lung adenocarcinoma cell lines (A549, H322 and Hcc827) and one normal human embryonic lung fibroblasts cell line (HLF) were obtained from American Type Culture Collection (ATCC, Manassas, VA). All Cells were cultured in ATCC-recommended medium supplemented with 10% fetal bovine serum (FBS) and maintained at 37°C in a humidified atmosphere containing 5% CO2.This work was supported by grants from the National Natural Science Foundation of China (81173453), Natural Science Foundation of Liaoning Province, China (2016, to Gu Chundong) and Municipal Science and Technology Program of Dalian, China (2012E15SF141). Appreciate Dr. Sun from the First Affiliated Hospital of Dalian Medical University for pathological assistance.CONFLICTS OF INTERESTThe authors declare no conflict of interest.