Piceatannol

Piceatannol is a selective Syk inhibitor with IC50 of ~10 μM. Piceatannol is a plant secondary natural product which inhibits the purified thymocyte p40 kinase (the catalytic fragment of Syk), by competing for the peptide or protein substrate binding site with Ki of 15 μM. Piceatannol also inhibits the activity of the p56lck protein-tyrosine kinase in LSTRA cell membranes or intact cells. Piceatannol preferentially inhibits the activity of Syk in comparison to Lyn in in vitro kinase assays. Selective inhibition of Syk by Piceatannol blocks receptor-mediated down-stream cellular responses (inositol 1,4,5-trisphosphate production, secretion, ruffling, and spreading). Piceatannol is a potent inducer of apoptosis in the lymphoma cell line BJAB by causing a concentration-dependent activation of caspase-3 and mitochondrial permeability transition. Piceatannol but not resveratrol is a very efficient inducer of apoptosis in ex vivo assay with leukemic lymphoblasts of 21 patients suffering from childhood lymphoblastic leukemia (ALL). Piceatannol inhibits TNF-induced NF-κB activation and NF-κB-mediated gene expression through suppression of IκBα kinase and p65 phosphorylation. Piceatannol inhibits the growth of colorectal cancer cell lines and arrests Caco-2 cells in the S phase of the cell cycle. Sequential treatment with Piceatannol and Ara-C yields synergistic growth inhibitory effects against HL-60 cells because of remarkably increased Ara-CTP formation after Piceatannol preincubation. Exposure of different-stage PC-3 prostate cancer (CaP) cells to Piceatannol also results in cell-type-specific downregulation of mTOR and its upstream and downstream effector proteins, AKT and eIF-4E-BP1.