PLK1 and cancer: Compared with the PBS and M1-20mut groups, the intraperitoneal injection of M1-20 resulted in the inhibition of cancer growth (Fig. 6B), and significantly reduced the size and weight of engrafted cancers (Fig. 6C), corresponding to the decreased levels of proliferation-related CDC25B, PLK1, PCNA, and increased levels of apoptosis-related Bax and Caspase 3 in M1-20-treated cancer samples (Supplemental Fig. 9A, B).