ESR1 and breast cancer: All of the 10 upregulated hub genes (CDK1, CCNB1, CCNA2, CDC20, TOP2A, CCNB2, MAD2L1, BUB1, KIF11, and RRM2) were dramatically upregulated in breast cancer, whereas five of the 10 downregulated hub genes (ESR1, IGF1, PDGFRB, PXN, and ZEB1) were significantly downregulated in breast cancer.