As the half maximal inhibitory concentration (IC50) of PCNA-I1 in cancer cell growth (IC50, 0.17 ± 0.07 μM) is low enough compared to normal cell growth (IC50, 1.60 ± 0.36 μM), PCNA-I1 together with other PCNA-Is can be used as potential PCNA-targeted cancer therapies [82,84]. Here, PCNA is linked to cancer.