Figure 6 Construction of protein–protein interaction (PPI) network and identification of the top genes. (A) The PPI network of DEIOSGs. According to the importance of key nodes, the top 3 are selected as hub genes. Since the third of the top 3 had 2 genes in our research, 4 genes (MMP2, COL1A1, CASP3, and HIF-1α) were actually obtained. (B) Expression of hub genes in GSE96804. (C) The receiver operating characteristic (ROC) curves of hub genes in GSE96804. (D) Validation of hub genes in the external dataset GSE30528. Except for COL1A1, the area under the ROC curve areas of all other genes were >0.7 in the GSE30528 dataset. (R version 4.2.1.).