Induction of Apoptosis by Sphingosine, Sphinganine, and C₂-Ceramide in Human Colon Cancer Cells, but not by C₂-Dihydroceramide

C2-ceramide generates DNA fragmentation, indicative of apoptosis, in HCT-116 human colon cancer cells, whereas C₂-dihydroceramide has no effects. Subconfluent HCT-116 cells were cultured without sphingolipids (control, Ctr), or with C₂-ceramide (Cer), or C₂-dihydroceramide (Dhcer) at 20 μM for 24 h. The DNA was extracted and analyzed using gel electrophoresis on a 2% agarose gel at 100 V. M, DNA marker (123 bp).

Sphingoid bases arrest the cell cycle at G₂/M phase in HCT-116 human colon cancer cells. Subconfluent cells were cultured in the absence (control, Ctr) or presence of sphingosine (SO) and sphinganine (SA) at 35 μM for 12 h. The DNA was then stained with propidium iodide, the cell cycle was examined via flow cytometric analysis, and the percentage of cells in each stage of the cell cycle was determined using the multi-cycle DNA content and cell cycle analysis software. The A₀ (sub-G₀/G₁) cell population was not included in the calculation of the cell population. Representative data are the mean±SEM (n=2).