Cytochrome C-dependent Fas-independent apoptotic pathway in HeLa cells induced by Δ12-prostaglandin J2

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Abstract
Cyclopentenone prostaglandins (PGs) have antiproliferative activity on various tumor cell growth in vitro. Particularly, 9-deoxy-(9,12)-13,14-dihydro PGD2( Δ12-PGJ2) was reported for its antineoplastic and apoptotic effects on various cancer cells, but its mechanism inducing apoptosis is still not clear. In this study, we have characterized apoptosis induced by Δ12-PGJ2in HeLa cells. Treatment of Δ12-PGJ2induced apoptosis as indicated by DNA fragmentation, chromatin condensation, and formation of apoptotic body. We also observed release of cytochrome c from mitochondria and activation of caspase cascade including caspase-3, -8, and -9. And the pan-caspase inhibitor z-Val-Ala-Asp (OMe) fluoromethyl-ketone (z-VAD-fmk) and Q-Val-Asp (OMe)-CH2-OPH (Q-VD (OMe)-OPH) prevented cell death induced by Δ12-PGJ2 showing participation of caspases in this process. However, protein expression level of Bcl-2 family was not altered by Δ12-PGJ2, seems to have no effect on HeLa cell apoptosis. And ZB4, an antagonistic Fas-antibody, exerted no effect on the activation of caspase 8 indicating that Fas receptor-ligand interaction was not involved in this pathway. Treatment of Δ12-PGJ2 also leads to suppression of nuclear factor κB (NF-κB) as indicated by nuclear translocation of p65/RelA and c-Rel and its DNA binding ability analyzed by EMSA. Taken together, our results suggest that Δ12-PGJ2-induced apoptosis in HeLa cell utilized caspase cascade without Fas receptor-ligand interaction and accompanied with NF-κB inactivation.

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