OSU-03012 (AR-12)

OSU-03012 induces apoptotic death in PC-3 cells with IC50 of 5 µM and reduces the activity of immunoprecipitated p70^S6K. OSU-03012 completely suppress cell growth in a diverse range of tumor cell lines at concentrations of 3–5 μm, as compared with the concentration of at least 50 μm. ^[1] OSU-03012 promotes cell killing to a greater extent in glioma cells than in nontransformed astrocytes. OSU-03012 causes a dose-dependent induction of cell death that is not altered by p53 mutation, expression of ERBB1 VIII, or loss of phosphatase and tensin function due to a homolog deletion on chromosome 10. OSU-03012 and ionizing radiation cause an additive, caspase-independent elevation in cell killing. OSU-03012 lethality as a single agent or when combined with signaling modulators is not modified in cells lacking expression of BIM or of BAX/BAK. OSU-03012 promotes the release of cathepsin B from the lysosomal compartment and that of AIF from mitochondria. The lethality of OSU-03012 is attenuated in protein kinase R-like endoplasmic reticulum kinase-/- cells, which correlated with the reduced cleavage of BID and suppression of cathepsin B and AIF release into the cytosol. ^[2] OSU-03012 inhibits thyroid cancer cell (NPA, WRO, and ARO cells) proliferation, migration and induces apoptosis, which results in an increase of cells in the S phase without an increase of cells in G2. OSU-03012 is an ATP-competitive inhibitor of PAK activity and suppresses the phosphorylation of AKT in thyroid cancer cells. ^[3] OSU-03012 inhibits cell growth of hepatocellular carcinoma cell lines including Huh7, Hep3B and HepG2 cells with IC50 values below 1 μM. OSU-03012 does not suppress PDK1 or AKT activity or induce cellular apoptosis but induces autophagy in Huh7 cells. Moreover, accumulation of reactive oxygen species (ROS) is detected after OSU-03012 treatment. ^[4] A recent study shows that OSU-03012 could enhance the susceptibility of (Bcr)-Abl mutant cell lines to -induced apoptosis. ^[5]

The effect of OSU-03012 on PC-3 cell viability is assessed by using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assay in six replicates. Cells are grown in 10% FBS- supplemented RPMI 1640 in 96-well, flat-bottomed plates for 24 hours. They are exposed to various concentrations of OSU-03012 (0-10 μM) dissolved in DMSO (final concentration ≤0.1%) in 1% serum-containing RPMI 1640 for different time intervals (~72 hours). Controls receive DMSO vehicle at a concentration equal to that in OSU-03012-treated cells. The medium is removed and replaced by 200 μL of 0.5 mg/mL 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide in 10% FBS-containing RPMI 1640. The cells are incubated in the CO₂ incubator at 37 °C for 2 hours. Supernatants are removed from the wells, and the reduced 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide dye is solubilized in 200 μL DMSO per well. Absorbance at 570 nm is determined by using a plate reader.

OSU-03012 suppresses tumor growth by 57.59% and increases cleaved LC3 in Huh7 tumor xenografts at 200 mg/kg. ^[4] OSU-03012 remarkably decreases expression of EGFR protein in the tumors by 48% compared with vehicle controls and also prevents YB-1 from binding to the EGFR promoter in MDA-MB-435/LCC6 xenografts. ^[6] OSU-03012 is well tolerated and inhibits the growth of HMS-97 schwannoma xenografts by 55% after oral administration. ^[7]