PBK and malignant colon neoplasm: Treatment of HCT‐15, HCT‐116, SW 620, or DLD‐1 colon cancer cells with acetylshikonin decreased the levels of phosphorylated TOPK (Thr9), phosphorylated ERK (Thr202/Tyr204), phosphorylated RSK (Ser380), and phosphorylated c‐Jun (Ser73; Figure 4a).