ATF3 and breast cancer: After the analysis of ATF3 expression level in different cell lines, it was found out that the mRNA expression level of ATF3 was also remarkably higher in breast cancer cell lines T47D, ZR751, MCF7, HBL100 and SUM159 than that in normal human mammary epithelial cell line MCF10A (all P < 0.05, Figure 2C).