Dinaciclib (SCH727965)S2768

Dinaciclib is also a potent DNA replication inhibitor that blocks thymidine (dThd) DNA incorporation in A2780 cells with IC50 of 4 nM. Dinaciclib strongly suppresses phosphorylation of Rb on Ser 807/811 at concentrations >6.25 nM, which is in agreement with the observation that 4 nM concentrations are required for 50% inhibition of dThd DNA incorporation in the same cell model. Significantly, complete suppression of Rb phosphorylation is correlated with the onset of apoptosis, as indicated by the appearance of the p85 PARP cleavage product in cells exposed to >6.25 nM Dinaciclib. Dinaciclib is active against a broad spectrum of human tumor cell lines. ^[1] Addition of Dinaciclib during hydroxyurea exposure also suppresses accumulation of γ-H2AX, in a dose-dependent manner. ^[2] Dinaciclib inhibits melanoma cell proliferation, and drives melanoma cells into massive apoptosis. ^[3] Dinaciclib induces the apoptosis of several osteosarcoma cell lines including those resistant to doxorubicin and dasatinib. Dinaciclib attenuates the phosphorylation of RNAP II at serine 2 and the phosphorylation of the CDK inhibitor p27^Kip1 at threonine 187. Reductions in phosphorylation activity occurrs at 12 - 40 nM Dinaciclib (4 to 16 hours post-Dinaciclib addition). Dinaciclib also reduces the phosphorylation of Rb at serine 807/811. Dinaciclib induces the apoptosis of mock- and p53-depleted U2OS cells to a similar extent. ^[4]