Research paperSOX9 promotes nasopharyngeal carcinoma cell proliferation, migration and invasion through BMP2 and mTOR signaling
Introduction
Nasopharyngeal carcinoma (NPC) is one of the most common malignancies occurring in southern China. Although NPC patients in stage I and stage II have better therapeutic outcomes, about 85% of NPC patients are initially diagnosed when they are in stage III and IV (Tsao et al., 2017). Late stage NPC is often poorly differentiated and highly malignant, leading to distant metastasis, which is the primary cause of NPC treatment failures (Liu et al., 2017). Discovering novel therapeutic targets and exposing the underlying mechanisms will greatly improve the clinical treatment of NPC metastases.
SRY-related high-mobility-group box family is a group of transcription factors that mediate cell fate by activating genes that maintain pluripotency, direct cell lineage differentiation, and sustain adult tissue homeostasis (Symon and Harley, 2017). SOX9 and SOX10 compose SOX transcription group and share a bipartite transactivation mechanism (Haseeb and Lefebvre, 2019). SOX10 was shown to induce epithelial-mesenchymal transition and contribute to NPC progression (He and Jin, 2018). However, the role of SOX9 in NPC was still unknown. Evidence has shown that SOX9 regulates some of its target genes through large clusters of transcriptional enhancers abundant in Histone H3 acetylated at lysine 27 (H3K27ac) (Zhang et al., 2016). Through this regulation pattern, SOX9 controls many cancer cell processes, including cell metastasis. SOX9 directly binds to the promoter of COL10A1 and activates its transcription, resulting in the invasion and metastasis of gastric cancer (Li et al., 2018). SOX9 also binds to the promoter of S100P, resulting in the overexpression of S100P and enhanced invasiveness and metastasis of colon cancer cells (Shen et al., 2015). However, the biological functions of SOX9 in NPC remain unclear.
In the present study, we evaluated the role of SOX9 in the migration and invasion of NPC cells. Moreover, SOX9-endowed migration and invasion abilities were induced by its direct binding to the promoter of BMP2 and enhanced BMP2 expression, followed by BMP2-induced mTOR signaling activation. Taken together, our results provide an understanding of novel anti-metastatic therapeutic strategies in NPC by targeting SOX9.
Section snippets
Cell lines and cell culture
NPC cell lines 6-10B and 5-8F were purchased from the Typical Culture Preservation Commission Cell Bank (Chinese Academy of Sciences, Shanghai, China). Cells were cultured in Dulbecco's Modified Eagle medium (DMEM) supplemented with 10% fetal bovine serum (Gibco, USA), 100 μg/ml streptomycin, and 100 U/ml penicillin.
Plasmid construction
The full-length cDNA of human SOX9 or BMP2 was cloned into the pSin-puro vector (Focus Bioscience Co., Ltd., Nanchang, China). All recombinant plasmids were verified by DNA
The expression of SOX9 is up-regulated in NPC tissues and cell lines
To evaluate the expression of SOX9 in NPC tissues, we obtained SOX9 expression data for 30 NPC tissues and 10 adjacent non-tumorous tissues from the Oncomine database (https://www.oncomine.org/resource/login.html). SOX9 expression was significantly higher in NPC tissues than in the adjacent non-tumor tissues (P < 0.001) (Fig. 1A). To analyze further SOX9 expression in NPC cell lines, we prepared five NPC cell lines (CNE1, Hone1, Sune1, 6-10B and 5-8F) and the NP69 nasopharyngeal epithelial
Discussion
In the present study, we noted that the expression of SOX9 was up-regulated in NPC tissues and NPC cells. Interestingly, the expression of SOX9 is higher in NPC cells with high metastasis potential, such as 5-8F and Hone1, but lower in cells with low metastasis potential, such as 6-10B. The ectopic expression of SOX9 was also observed in late stage NPC patients (stage IV). Exogenetic expression of SOX9 promoted NPC cell 6-10B proliferation, migration and invasion, while siRNA-mediated knockdown
Conclusion
Our study demonstrated for the first time that SOX9 is upregulated in NPC and contributes to cell proliferation, migration and invasion through directly enhancing the transcription of BMP2 and subsequently activating mTOR signaling. This study provides strategies for targeting SOX9 that might be considered as novel clinic treatments for NPC.
Funding information
The Military Logistics Research Project (number CWH17C017 to Linhai Li) Science and Technology Program of Guangzhou, China (number 201804010186 to Bin Xiao) the Natural Science Foundation of Guangdong Province, China (number 2018A030310014 to Bin Xiao) the National Natural Science Foundation of China (NSFC) (number 81802634 to Bin Xiao).
Declaration of Competing Interest
The authors declare that no conflicts of interest exist.
Acknowledgements
We thank Focus Bioscience Co., Ltd. (Nanchang, China) for kindly providing the plasmids used in this study.
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2020, GeneCitation Excerpt :During ovarian development, BMP2 expression is regulated by FOXL2 and the Wnt signaling pathway factor Wnt4 (Kashimada et al., 2011). In nasopharyngeal carcinoma cells, the transcription factor Sox9 directly binds to the bmp2 promoter region to promote its expression (Xiao et al., 2019), and BMP2 can promote the proliferation and invasion of nasopharyngeal carcinoma cells by activating the mTORC1 signaling pathway (Wang et al., 2017; Xiao et al., 2019). We know that the network of signals in cells is intricate.
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These authors contributed equally to this work.