. In addition, a volcano plot was made by using the ggplot2 package to identify the differential expression genes (DEGs) with statistical significance between the tumor and nontumor groups. Hierarchical clustering and heatmap plot analyses were performed for the DEGs of DElncRNAs, DEmiRNAs, and DEmRNAs by using ComplexHeatmap \[[@B14]\] package in R.

2.3. Collection of mRNA-lncRNA-miRNA Interactions Data {#sec2.3}
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The lncRNA-miRNA interactions data were predicted from the miRcode database (<http://www.mircode.org/>) and the starBase v3.0 (<http://starbase.sysu.edu.cn/>). The lncRNA-miRNA interactions were then obtained according to the intersection of the 2 databases. In addition, miRNA-mRNA interactions data were predicted using miRcode (<http://www.mircode.org/>), miRDB (<http://www.mirdb.org/>), miRanda (<http://www.microrna.org/microrna/home.do>), miRTarBase (<http://mirtarbase.mbc.nctu.edu.tw/>), and TargetScan database (<http://www.targetscan.org/>). The intersection of the lncRNA-miRNA interaction pairs predicted by at least 3 of these databases was considered as the final lncRNA-miRNA interactions.

2.4. Constructing the ceRNA Network Analysis {#sec2.4}
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To investigate the potential interactions between lncRNAs and mRNAs, we constructed the ceRNA coregulated network using DElncRNAs, DEmiRNAs, and DEmRNAs. The coexpression analysis was performed by using Pearson\'s correlation coefficient (PCC) to identify correlation pairs according to the expression levels between significantly dysregulated DElncRNAs and DEmRNAs. The Pearson correlation cutoff value \>0.7 or \<−0.7 with *P* \< 0.001 was defined as the screening threshold for retaining the RNAs in the analysis. Finally, the coregulated network was constructed using Cytoscape (version 3.7.0) \[[@B15]\] to illustrate the ceRNA network.

2.5. GO and KEGG Functional Enrichment Analysis of DEGs {#sec2.5}
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