OSU-03012, a Novel Celecoxib Derivative, Is Cytotoxic to Myeloma Cells and Acts through Multiple Mechanisms

Abstract

OSU-03012 is a novel celecoxib derivative, without cyclooxygenase-2 inhibitory activity, capable of inducing apoptosis in various cancer cells types, and is being developed as an anticancer drug. We investigated the in vitro activity of OSU-03012 in multiple myeloma (MM) cells. U266, ARH-77, IM-9, and RPMI-8226, and primary myeloma cells were exposed to OSU-03012 for 6, 24, or 72 h. Cytotoxicity, caspase activation, apoptosis, and effects on intracellular signaling pathways were assessed. OSU-03012 was cytotoxic to MM cells with mean LC50 3.69 +/- 0.23 and 6.25 +/- 0.86 micromol/L and at 24 h for primary MM cells and cell lines, respectively. As a known PDK-1 inhibitor, OSU-03012 inhibited the PI3K/Akt pathway with downstream effects on BAD, GSK-3beta, FoxO1a, p70S6K, and MDM-2. However, transfection of MM cells with constitutively active Akt failed to protect against cell death, indicating activity against other pathways is important. Phospho (p)-signal transducers and activators of transcription 3 and p-MAP/ERK kinase 1/2 were down-regulated, suggesting that OSU-03012 also inhibited the Janus-activated kinase 2/signal transducer and activator of transcription 3 and mitogen-activated protein kinase pathways. Although expression of Bcl-2 proteins was unchanged, OSU-03012 also down-regulated survivin and X-linked inhibitor of apoptosis (XIAP), and also induced G2 cell cycle arrest with associated reductions in cyclins A and B. Finally, although OSU-03012 induced cleavage of caspases 3, 8 and 9, caspase inhibition did not prevent cell death. We conclude that OSU-03012 has potent activity against MM cells and acts via different mechanisms in addition to phosphoinositide-3-kinase/Akt pathway inhibition. These studies provide rationale for the clinical investigation of OSU-03012 in MM.