In MCF7 cells, which belong to the estrogen receptor (ER) positive human breast cancer (BC) cell line with a positive response to estrogen induction, ERα-E2 (17β-estradiol) directly upregulates CXXC5 expression through the interaction with estrogen response element (ERE), and CXXC5 subsequently regulates the expression of downstream genes in an estrogen-dependent or independent manner [23, 24]. This evidence concerns the gene ESR1 and breast cancer.