PTPN23-dependent activation of PI3KC2α is a therapeutic vulnerability of BRAF-mutant cancers.

Abstract

BRAF mutations drive initiation and progression of various tumors. While BRAF inhibitors are effective in BRAF-mutant melanoma patients, intrinsic or acquired resistance to these therapies is common. Here, we identify non-receptor-type protein tyrosine phosphatase 23 (PTPN23) as an alternative effective target in BRAF-mutant cancer cells. Silencing PTPN23 selectively kills BRAF-mutant melanoma cells but not those with wild-type BRAF. Mechanistically, PTPN23, a catalytically inactive phosphatase, intriguingly induces WNK3-mediated phosphorylation of phosphoinositide 3-kinase class II alpha (PI3KC2α) at serine 329, enhancing its catalytic activity. This activation promotes production of PI(3,4)P2 and subsequent AKT2 activation at endosomes to support cell survival. Genetic or pharmacological targeting of the PTPN23-PI3KC2α-AKT2 signaling axis, alone or in combination with BRAF inhibitors, effectively inhibits the growth of BRAF-mutant melanoma and other cancers in vitro and in vivo. We also demonstrate that melanocyte-specific knockout of PTPN23 significantly inhibits BRAFV600E-driven melanomagenesis. Altogether, our findings demonstrate that targeting PTPN23/PI3KC2α offers a new and viable therapeutic strategy for BRAF-mutant cancers.