PTPIP51 inhibits non-small-cell lung cancer by promoting PTEN-mediated EGFR degradation

Protein tyrosine phosphatase interacting protein 51 (PTPIP51) interacts with two non-receptor tyrosine phosphatases and induces apoptosis. In the present study, we showed that PTPIP51 is downregulated in non-small cell lung cancer (NSCLC), and its elevated expression correlates with improved outcomes. PTPIP51 overexpression in NSCLC cells significantly inhibits downstream epidermal growth factor receptor (EGFR) signaling in PI3K/Akt, RAS/RAF/ERK, and JAK/STAT3 pathways. The efficacy of the EGFR inhibitor gefitinib improves in combination with PTPIP51 to accelerate apoptosis and inhibit NSCLC growth in vivo and in vitro. Here, we demonstrated that PTPIP51 interacts with phosphatase and tensin homolog (PTEN) to form a PTPIP51-PTEN-CK2 complex, which induces phosphorylation of the C-tail region of PTEN (p-PTEN Thr382 and Thr383). This subsequently induces ubiquitylation of EGFR and its degradation via lysosomes. Therefore, PTPIP51 acts as a tumor suppressor in NSCLC by inducing PTEN phosphorylation and by promoting EGFR degradation.