Fenretinide stimulates redox-sensitive ceramide production in breast cancer cells: potential role in drug-induced cytotoxicity

The synthetic retinoid N-(4-hydroxphenyl) retinamide (4HPR) has manifold actions, which may contribute to its chemopreventive effects on breast cancer cell growth and progression. A role for ceramide as a stress-response signal is investigated here during the cytotoxic action of 4HPR in MCF-7 cells. N-(4-hydroxphenyl) retinamide induced a dose-dependent decline in cell growth and survival associated with a maximal 10-fold increase in ceramide production at 10 muM. N-(4-hydroxphenyl) retinamide exhibited a greater potency than all-trans retinoic acid (ATRA) on growth inhibition and ceramide production. The synthetic peroxisome proliferator-activated receptors agonist troglitazone (TGZ), but not the native ligand 15-deoxy-delta 12,14-prostaglandin J(2), abrogated both these actions of 4HPR but not that of ATRA. The antioxidant N-acetylcysteine mimicked the abrogative effect of TGZ on 4HPR action, while the exogenous oxidant H2O2 also stimulated ceramide production. The inhibitors of de novo ceramide synthesis, fumonisin B-1 and myriocin, blocked the ceramide response to 4HPR and partially reversed the apoptotic response, but did not prevent the overall decline in cell survival. The pancaspase inhibitor Z-VAD fmk reduced the decrease in cell survival caused by 4HPR, but did not affect the ceramide response. These findings describe a novel redox-sensitive elevation of ceramide levels associated with the cytotoxic response of breast cancer cells to 4HPR. However, a major mediatory role for this sphingolipid in this context remains equivocal.