BPR0Y007, a bis-benzylidenecyclopentanone derivative (2,5-bis- (4-hydroxy-3-methoxybenzylidene) cyclopentanone), was identified in our laboratory as a novel
antineoplastic agent with a broad spectrum of antitumor activity against many human
cancer cells. A previous study showed that
BPR0Y007 inhibited
DNA topoisomerase I (Top 1) activity and prevented
tubulin polymerization. Notably, no cross-resistance with
BPR0Y007 was observed in
camptothecin-, VP-16- or
vincristine-resistant cell lines. In this study, we further investigated the cellular and molecular events underlying the antitumoral function of this compound in human oral
epidermoid carcinoma KB cells, focusing on the early cytotoxic effect. Treatment of KB cells with BPR0Y007-induced G(2)/M phase arrest followed by sub-G(1) phase accumulation.
Annexin-V-
propidium iodide (PI) binding assay and DNA fragmentation assay further indicated that BPR0Y007-induced cell death proceeded through an apoptotic pathway as opposed to via
necrosis. This compound produced a time-dependent activation of caspases-3 and -8, however, another
caspase-3 initiator,
caspase-9, was only marginally activated at later time point. We further demonstrated that the activation of the
caspases cascade and nuclear fragmentation was not associated with inactivated Bcl-2 and perturbed mitochondrial membrane potential by
BPR0Y007. The finding that BPR0Y007-induced apoptosis through a membrane-mediated mechanism was supported by up-regulated expression of Fas (CD95/APO-1), but not Fas-L. Furthermore, up-regulation of p53 and its affected gene, MDM2, in KB cells was found after
BPR0Y007 exposure. Overall, our results demonstrated that the
BPR0Y007 could induce an early cytotoxic apoptosis through a caspase-8-dependent but mitochondrial-caspase-9 independent pathway, and involving upregulation of p53.