To investigate whether inhibition of one of the PI3K isoforms is sufficient to sensitize cancer cells to TRAIL-induced apoptosis, we treated HeLa cells with TRAIL in the presence or absence of pharmacological inhibitors that have been reported to be isoform specific (PIK-75 (p110α), TGX-221 (p110β), AS-252424 (p110γ) and IC-87114 (p110δ)) (for IC50 values see Supplementary Figure S1a). Here, PIK3CD is linked to cancer.