CCNE1 and breast cancer: In our analysis, CCNE1 was significantly upregulated in BRCA1/2-mutant BC, compared with wild-type BC, suggesting that BRCA1/2 genes could regulate cell cycle in tumors via CCNE1 reflected by the fact that cell cycle phase transition, especially cell cycle G1/S transition were significantly enriched in mutant breast cancer from the GSEA results.