Fenretinide activates caspases and induces apoptosis in gliomas

The synthetic retinoid fenretinide (N-[4-hydroxyphenyl] retinamide or 4HPR) has been shown to not only inhibit cell growth but also to induce apoptosi s in a variety of malignant cell lines. It is being tested presently for it s potential as a chemopreventive agent against several cancers, A related r etinoid, 13-cis-retinoic acid (cRA), has been shown to have activity agains t gliomas in vitro as well as in a recent clinical study. The present study aimed at assessing the activity of fenretinide against glioma cells in vit ro and comparing it with that of cRA at pharmacologically relevant doses. W e hypothesized that the ability of fenretinide to induce apoptosis would ma ke it more potent against gliomas than cRA, Four glioma cell lines (D54, U2 51, U87MG, and EFC-2) were treated with fenretinide (1-100 mu M) and showed dose- and time-dependent induction of cell death. At pharmacologically rel evant doses, fenretinide was more active against glioma cells than cRA beca use of its ability to induce apoptosis, Flow cytometric studies using D54 c ells demonstrated no significant changes in the cell cycle distribution com pared with untreated control, but a sub-G, fraction consistent with apoptos is was detected, Terminal deoxynucleotidyl transferase-mediated nick end la beling assay indicated that the apoptotic fraction was cell cycle nonspecif ic. Fenretinide treatment resulted in cleavage of poly ADP-ribose polymeras e, indicating an activation of the caspase 3, Immunofluorescence studies us ing the nuclear stain 4',6-diamidine-2'-phenylindole dihydrochloride showed nuclear condensation and an apoptotic morphology, Hence, this study demons trates that, at clinically relevant doses, fenretinide is a potent inducer of apoptosis in gliomas acting via the caspase pathway. We also show that a t clinically achievable doses, fenretinide has more activity against glioma s than comparable doses of cRA, The favorable side effect profile seen in p revious clinical studies and the in vitro activity against gliomas demonstr ated in this study suggest that fenretinide could be a promising therapeuti c agent against gliomas.