STUB1 and cancer: More importantly, we proposed p42 as an inhibitor of phosphoinositide 3-kinase (PI3K), a well-known oncogene in various human cancers, through degradation of the p85 regulatory domain of PI3K, and demonstrated that p42 dramatically reduced p85 protein levels by linking p85 to proteasomal degradation mediated by the HSP70/CHIP E3 ligase complex12.