SI-2 targets the receptor-interacting domain (RID) of steroid receptor coactivators (SRCs) and suppresses cellular transcriptional activity (Effec. conc. >/= 5 nM in cell-based SRC-1, SRC-2, and SRC-3 reporter assays) by downregulating SRCs protein, but not transcript level (Effec. conc. >/= 12.5 nM against SRC-3, >/= 25 nM against SRC-1 and SCR-2 in MDA-MB-468 culture). SI-2 is cytotoxic to breast cancer cultures (IC50 = 1.5 nM/BT-474, 3.4 nM/MDA-MB-468, 22 nM/MCF-7), but not to normal hepatocytes even at 500 nM concentration. SI-2 is reported to be orally available in mice and, when administered intraperitoneally (2 mg/kg b.i.d.), effectively suppress MDA-MB-468-derived tumor expansion in mice in vivowith good pharmacokinetics (Cmax = 30 μM, tmax = 0.25 h, t1/2 = 1.0 h; 20 mg/kg i.p.) and no apparent adverse effects to the animals.
SI-2 targets the receptor-interacting domain (RID) of steroid receptor coactivators (SRCs) and suppresses cellular transcriptional activity.
