One of the mechanisms explaining the ability of IGFBP-3 to potentiate breast cancer cell growth is the ability of IGFBP-3 to activate sphingosine kinase, an enzyme that incorporates phosphate group into sphingosine and the inhibition of sphingomyelinase, an enzyme that generates ceramide from sphingosine (Figure 4). The gene discussed is IGFBP3; the disease is breast carcinoma.