CCNE2 and breast cancer: The IHC map of CCRGs is shown in Figure 7 and confirmed that CCNE2, CCNB1, CCNB2, TTK, CDC20 and PTTG1 were significantly overexpressed in BC tissues compared with normal mammary tissues (p<0.05); however, BUB1B was not confirmed to be significantly overexpressed in BC tissues due to the lack of data available in the Human Protein Atlas.