The IC₅₀s for inhibition of the different catalytic subunits of class I PI3Ks by the compounds used in this study are listed. Chemical structures of the inhibitors are shown in Figure S1. Data have been drawn from the appropriate patent and publication information (see “Materials and methods”); concentrations of ATP used in the relevant in vitro PI3K assays were TGX-221 (100 μM), IC87114 (200 μM), YM-024 (2 μM), and AS-252424 (each PI3K isoform was assayed at its respective K_m for ATP—that is, 89 μM, 70 μM, 23 μM, and 59 μM for the α, β, γ, and δ isoforms, respectively). We have also generated analogous data comparing each of these compounds in the same in vitro assay at 2 μM ATP (Table S1).