Resveratrol suppresses cell proliferation via inhibition of STAT3 phosphorylation and Mcl-1 and cIAP-2 expression in HTLV-1-infected T cells

Adult T-cell leukemia (ATL) is an aggressive malignancy of peripheral T cells infected with human T-cell leukemia virus type 1 (HTLV-1). The prognosis of patients with aggressive ATL remains poor because ATL cells acquire resistance to conventional cytotoxic agents. Therefore, development of novel agents is urgently needed. We examined the effects of resveratrol, a well-known polyphenolic compound, on cell proliferation and survival of HTLV-1-infected T-cell lines, MT-2 and HUT-102. We found that resveratrol suppressed cell proliferation and induced cell death of MT-2 and HUT-102 cells. Immunoblot analysis showed inhibition of myeloid cell leukemia sequence (Mcl)-1 and cellular inhibitor of apoptosis protein (cIAP)-2 expression as well as signal transducers and activators of transcription (STAT) 3 phosphorylation at Tyr705 and Ser727 in resveratrol-treated cells. We also observed cleavage of caspase-3 and poly(ADP-ribose) polymerase in resveratrol-treated cells, indicating that resveratrol induces caspase-dependent apoptosis in MT-2 and HUT-102 cells. In addition, the STAT3 inhibitor S3I-201 not only induced cell growth arrest and cell death but also activated caspase-3 in MT-2 and HUT-102 cells, indicating that STAT3 may be a therapeutic target for ATL. These results suggest that resveratrol presents a potent anti-proliferative effect in part via the suppression of STAT3 phosphorylation and Mcl-1 and cIAP-2 expression in HTLV-1-infected T cells. Resveratrol merits further investigation as a potential chemotherapeutic agent for ATL.