Stat3 Inhibitor VIII, 5,15-DPP

Stat3 Inhibitor VIII, 5,15-DPP is a cell-permeable porphyrin compound that binds Stat3 (STAT3, K_D = 880 nM by SPR) and prevents Stat3 SH2 domain-mediated ligand binding (IC₅₀ = 280 nM) and dimerization (~60% inhibition at 50 μM in HEK293), while exhibiting much reduced activity against STAT1 ligand binding (IC₅₀ = 10 μM) and no activity againt Grb2 ligand binding even at concentrations as high as 20 μM. 5,15-DPP pre-treatment (50 μM) of MDA-MB-468 cultures is shown to greatly inhibit IL-6-induced Stat3, but not STAT1/5a/5b, nuclear translocation (by >90%) and nuclear Stat3 c-myc promoter binding activity, resulting in a more than 90% reduction in cellular c-myc protein level.