“…Of interest, sphingosine kinase (SPHK), the enzyme that catalyzes the phosphorylation of sphingosine, is activated by growth and survival factors, including platelet-derived growth factor (PDGF), serum [13], nerve growth factor [14], and vitamin D3 [15], as well as activation of protein kinase C [16], resulting in increased intracellular levels of SPP. Abundant evidence indicates that SPP promotes cell growth, proliferation, and resistance to apoptosis [17,18].…”