2.5. PPI network and module analysis

The STRING database (Search Tool for the Retrieval of Interacting Genes https://string-db.org)^[7–10] is commonly performed to predict and trace out PPI network in bioinformatics. We uploaded significant genes into website and downloaded information for further analysis. Cytoscape (version 3.6.0), a free visualization software, was used to examine relationship between these DEGs (maximum number of interactors = 0 and confidence score ≥0.4). Meanwhile, MCODE software in Cytoscape was applied to screen central nodes in PPI network (degree cut-off = 2, node score cut-off = 0.2, k-core = 2, and maximum depth = 100).