With the emergence of chemical biology, the use of pharmacological inhibitors in biological research has been expanding. SP600125 is a low-molecular weight compound that has been widely used to inhibit c-Jun-N-terminal kinase (JNK). A recent publication by Tanemura et al. (J. Biochem. 145:345-354, 2009) indicated that SP600125 also inhibits phosphatidylinositol 3-kinase (PI3K) in an isoform-sel...