Figure 1.

Sphingosine and sphingosine-1-phosphate (S1P), but not ceramide (Cer), are upregulated by ionizing radiation. PPC-1 prostate cancer cell cultures were irradiated (mock or 5 Gy) and collected at the indicated time points after irradiation. Cell pellets and culture media were prepared and lipids were extracted for mass spectrometry as mentioned in Materials and Methods. (a) Intracellular C₁₆ Cer (shaded bars), C₂₄ Cer (hatched bars), sphingosine (Sph, striped bars), S1P (diamond bars), and total Cer (dotted bars) expression levels are represented as percent of nonirradiated cells. (b) S1P levels in PPC-1 culture media from irradiated or control cells. Results shown are mean ± SD of three replicates from one of two independent, representative experiments. ^*P < 0.05, ^**P < 0.01 compared with nonirradiated cells.