Fenretinide (4-HPR) is a synthetic retinoid that is cytotoxic to several T-cell acute lymphoblastic leukemia (ALL) cell lines, and has demonstrated activity in a variety of cancer cell lines in vitro. Reported mechanisms of action for fenretinide include both increased reactive oxygen species (ROS) generation in some cell lines and increased dihydroceramide levels. Dihydroceramides are the product of N-acylation of sphinganine with fatty acid chains varying in carbon length and degree of saturation. Although synthetic, short-acyl chain dihydroceramides have been reported to be non-cytotoxic in cell culture in vitro, the cytotoxic potencies of native-acyl chain dihydroceramides are unknown. In the current study, increased synthesis of specific native-acyl chain dihydroceramides was targeted through a novel cell culture method employing concurrent exogenous administration of sphinganine, GT-11, a dihydroceramide desaturase inhibitor, and specific individual fatty acids. Sphingolipids were analyzed using LC/MS/MS. Cytotoxicity was measured using the fluorescence-based cytotoxicity assay DIMSCAN. Non-parametric correlation analysis of cytotoxicity and absolute sphingolipid levels revealed a strong positive correlation between cytotoxicity and C22:0-dihydroceramide (α = 0.75, P < 0.001) and C24:0-dihydroceramide (α = 0.84, P < 0.001) in the CCRF-CEM ALL cell line, with similar results observed independently in MOLT-4, COG-LL-317 and COG-LL-332 ALL cell lines. Additionally, fenretinide cytotoxicity was significantly increased by co-treatment with C22:0-fatty acid in association with an increase of C22:0- and C24:0-dihydroceramides. These findings suggest that the addition of specific fatty acids, perhaps in a tumor-type specific manner, through simple dietary or intravenous supplementation, or via concurrent incorporation into drug delivery vehicles, may improve the clinical efficacy of dihydroceramide-increasing anticancer agents, such as fenretinide.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4661. doi:1538-7445.AM2012-4661