According to the IC50 data in Table 2, in several cancer cell lines, the Skp2 inhibitor exerted stronger inhibitory effects than the Skp2-inhibiting compounds, especially the natural Skp2 inhibitor gentian violet, which disrupted the binding between Skp2 and p27, with a IC50 of 0.4 μM in human cervical cancer cell HeLa, and 0.6 μM in murine breast cancer cell tsFT210, comparing to the 5.3 μM in normal NIH3T3 cells (Ooi et al., 2013). Here, CDKN1B is linked to breast carcinoma.