To study the mechanism of paeoniflorin toxicity on ER + BC cells, we detected the expression of the SIRT4 protein in T47D and MCF-7 cells after stimulating them with 60 μM of paeoniflorin for 48 hours and found that paeoniflorin strongly increased the SIRT4 expression in both cell lines (Figure 4(a)). Here, SIRT4 is linked to breast cancer.