It was revealed that there was a distinct drop in the number of apoptosis cells in the si-circRASSF2 group (Figure 3(d), p < 0.01); PCNA protein expression was significantly decreased, and the protein levels of cleaved-PARP and cleaved-caspase3 were significantly increased in the cells (Figure 2(e), p < 0.01), suggested that the decrease of circRASSF2 expression can promote apoptosis in BC cells. Here, PCNA is linked to breast cancer.