As shown in Fig. S7, overexpression of HDAC1 or E2F1 partially reversed the inhibitory effect of HR488B on cell viability and the co-expression of HDAC1 and E2F1 was more effective to reverse the inhibitory effect of HR488B, which confirmed that HR488B executed its anti-cancer effect via the HDAC1-E2F1 axis. Here, E2F1 is linked to cancer.