PIK3CA and cancer: PIP3 in turn activates protein kinase B (AKT) and downstream molecules, leading to the promotion of cell growth, proliferation, and survival.7 In many types of cancer cells, the PI3K‐AKT pathway is frequently activated through gain‐of‐function mutations in PIK3CA, which encodes p110α, the catalytic subunit of PI3K.8 Therefore, PI3K is considered a potential drug target for cancer therapy.9, 10 Although liphagal was reported to exhibit cytotoxic effects in human colon cancer cells,4 the effects of siphonodictyal B on human cancer cell have never been evaluated.