Effects of specific fatty acids on 4-HPR-induced dihydroceramide levels and cytotoxicity.

<p><i>A</i>) Effects on dihydroceramide levels. COG-LL-317h and COG-LL-332h cells were treated with 4-HPR (1 µM) with or without C18:0- or C22:0-fatty acids (5 µM) for six hours and sphingolipids analyzed. Data were normalized to cells that received 4-HPR without fatty acid supplementation and plotted as fold change (Z-axis). Significant (<i>P</i> ≤ 0.001) differences from 4-HPR without fatty acid indicated by asterisks (*). <i>B</i>) Effects on cytotoxicity. CCRF-CEM, MOLT-4, COG-LL-317h, and COG-LL-332h cell lines were treated with 4-HPR (0-9 µM) ± C18:0- or C22:0-fatty acids (5 µM) and cytotoxicity assessed at +48 hours by DIMSCAN cytotoxicity assay. Data were normalized to controls and represented as Survival Fraction (Y-axis). Error bar, SEM. Significant (<i>P</i> ≤ 0.001) differences in cytotoxicity from 4-HPR without fatty acid are indicated by asterisks (*).