PCNA and prostate cancer: Additionally, multiple proteins, such as PCNA, MCM6, MCM3, and MCM4, involved in the pathways of DNA replication and the cell cycle, were significantly downregulated in both the nifedipine and nortriptyline groups (Figure 5D), and consequently may play central roles in nifedipine- and nortriptyline-induced inhibition of cell proliferation in prostate cancer cells.