Sphingosine kinase isoforms, SPHK 1 and SPHK 2 , catalyze the phosphorylation of sphingosine to sphingosine-1-phosphate (S1P). S1P exhibits a broad spectrum of biological activities including cell proliferation, survival, migration, cytoskeletal organization, and morphogenesis.{11895,12477,10628} Sphingosine kinase inhibitor 2 is an inhibitor of sphingosine kinase 1 (SPHK1) with an IC50 value of 0.5 µM for non-ATP-competitive inhibition of human recombinant SPHK1.{11597} It is selective for SPHK1 over ERK2, PI3K, and PKC? at concentrations up to 60 µM. Sphingosine kinase inhibitor 2 inhibits proliferation of several cancer cell lines, including T-24, MCF-7, NCI/ADR, and MCF-7/VP (IC50s = 0.9-4.6 µM).