Figure 5.

ABTL0812 induces accumulation of long-chain dihydroceramides in cancer cells and tumors. (a) Scheme representing the pathway of de novo sphingolipid biosynthesis. Serine palmitoyltransferase (SPT) catalyzes the condensation of palmitoyl-CoA and serine to produce 3-ketosdihydrosphingosine. KDSR (3-ketodihydrosphingosine reductase) reduces 3-ketodihydrosphingosine to dihydrosphingosine. Then, ceramide synthases (CERSs) convert dihydrosphingosine into the different molecular species of dihydroceramides, which are transformed to ceramides by the insertion of a 4,5-trans double bond catalyzed by the enzyme DEGS1. (b) ABTL0812 effect on levels of total cellular ceramides and dihydroceramides. MiaPaca2 cells were treated with 100 µmol/L ABTL0812 for the times indicated, pelleted and lipid content extracted and analyzed by UPLC-TOF-Ms. Data are expressed in pmol of sphingolipid per 10⁶ cells. Each value is the mean ± SD of three different determinations. (c) Levels of molecular species of dihydroceramides at 6 h (left histogram) and 24 h of ABTL0812 treatment (right histogram) in MiaPaca2 cells. Each value is the mean ± SD of three different determinations. (d) Levels of dihydroceramides in endometrial cancer Ishikawa cells after 6 h of ABTL0812 treatment. Total dihydroceramides and molecular species are shown in the left and right panels, respectively. Each value is the mean ± SD of three different determinations. (e,f) ABTL0812 effect on levels of dihydroceramides in tumors. *, P < 0.05; **, P < 0.005; ***, P < 0.001 from vehicle-treated cells