Honokiol induces cell cycle arrest and apoptosis via inhibition of survival signals in adult T-cell leukemia

► Honokiol had cytotoxic activity against HTLV-1-infected T-cell lines and ATL cells. ► Honokiol reduced the expression of cyclins D1, D2, E, CDKs 2, 4, 6 and c-Myc. ► Apoptosis was induced via reduced expression of cIAP-2, XIAP and survivin. ► Honokiol was effective in mice harboring tumors of HTLV-1-infected T-cell origin. ► Inhibition of survival signals including NF-κB, AP-1, STATs and Akt confers effects.