Adenovirus-mediated E2F-1 gene transfer induces an apoptotic response in human gastric carcinoma cells that is enhanced by cyclin dependent kinase inhibitors

E2F-1 is a transcription factor that regulates cell cycle progression into S-phase. Deregulation of E2F-1 activity has been associated with cellular c ommitment to apoptosis. Also critical in the regulation of S-phase are the actions of the cyclin dependent kinases, Cdk2 and cdc2. Inhibition of these cyclin dependent kinases has been similarly associated with disrupting ord erly S-phase progression and causing subsequent apoptosis in certain cancer cells. In this study, we examine the ability of adenovirus-mediated E2F-1 overexpression to induce apoptosis in human gastric carcinoma cells. Furthe rmore, we investigate the effect of the cyclin dependent kinase inhibitors, olomoucine and roscovitine, on E2F-1-mediated apoptosis in human gastric c arcinoma cells. AGS and SNU-1 gastric adenocarcinoma cells were infected wi th adenoviral vectors expressing E2F-1 (Ad5CMVE2F-1) or control viruses exp ressing beta-galactosidase (Ad5CMVLacZ) or lacking a transgene (Ad5). Gastr ic adenocarcinoma cells were then independently treated with roscovitine or olomoucine. Finally, gastric adenocarcinoma cells were infected with the v arious adenoviral vectors in combination with roscovitine or olomoucine. E2 F-1 overexpression resulted in an 85% reduction in cell viability at 72 h c ompared to controls. Combining E2F-1 overexpression with roscovitine result ed in >99% reduction in cell viability by 72 h. Overexpression of E2F-1 res ulted in premature S-phase entry and G2/M arrest at 24 h, followed by apopt osis by 72 h. Combining E2F-1 overexpression with roscovitine resulted in a n earlier G2/M attest, followed by a more complete, widespread apoptotic re sponse by 24 h. Caspase 3/CPP32 activation and PARP cleavage in response to E2F-1 overexpression, alone and in combination with roscovitine, implicate the caspase cascade in E2F-1-mediated apoptosis of gastric cancer cells. B ar levels also increased in response to E2F-1 gene transfer, alone and in c ombination with roscovitine. E2F-1 overexpression induces widespread apopto sis in human gastric carcinoma cells. Combining E2F-1 overexpression with c yclin-dependent kinase inhibitors results in an enhanced apoptotic response , causing nearly complete gastric tumor cell death within 72 h. E2F-1 gene therapy in combination with cyclin dependent kinase inhibitors is a potenti ally active chemogene therapy strategy for the treatment of human gastric c ancer.