Importantly, the activity of another ceramidase enzyme, human alkaline ceramidase 2 (ACER2), which increases the levels of both Sph and S1P, while simultaneously decreasing the levels of Cer, has been shown to be involved in the p53–mediated DNA damage response, as well as in regulation of cell cycle arrest and cellular senescence in colon cancer cells [20]. The gene discussed is TP53; the disease is colonic neoplasm.