Oncogenic function of p34SEI-1 via NEDD4‑1‑mediated PTEN ubiquitination/degradation and activation of the PI3K/AKT pathway.

A 34-KD protein encoded by the SEI-1 gene (p34(SEI‑1)), is a relatively recently discovered oncoprotein that has multiple important biological functions. Our data show that p34(SEI-1) enhances cancer cell survival and promotes tumorigenesis by downregulating the tumor suppressor PTEN, a negative regulator of the PI3K/AKT signaling pathway, and therefore activating the PI3K/AKT signaling pathway. In this process, p34(SEI-1) positively affects NEDD4-1 gene expression both at the transcriptional and protein levels. Furthermore, the expression levels of p34(SEI-1) and NEDD4-1 were found to be coordinated in tumor tissues obtained from patients with breast cancer. We also show that p34(SEI-1) affects the subcellular localization of PTEN.