STUB1 and breast cancer: Furthermore, we provide convincing evidence that the C-terminal domain of p42 (fragments 183–394 and 280–394), which are able to bind HSP70/CHIP complex is sufficient for the tumor suppressor activity of p42 in glioma cells and certain breast cancer cells in vitro and in vivo; our data indicate that fragment 280–394 may be a minimal functional unit of p42 and might have implications for the design of peptide inhibitors of PI3K in the future.