PCNA and cancer: Furthermore, the other possible cause of the cytotoxic activity of BAPPN is the decrement of the cancer cell lines’ proliferation through downregulation of PCNA and Ki67, which are cell proliferation markers, in HepG2 cells (Figure 7C,D); HCT-116 cells (Figure 8C,D); MCF-7 (Figure 9); and A549 cells (Figure 10).