PTPN2 regulates the activation of KRAS and plays a critical role in proliferation and survival of KRAS-driven cancer cells

Zhangsen Huang,Mingzhu Liu,Donghe Li,Yun Tan,Ruihong Zhang,Zhizhou Xia,Peihong Wang,Bo Jiao,Ping Liu,Ruibao Ren

doi:10.1074/jbc.ra119.011060

Zhangsen Huang, Mingzhu Liu + Show 8 more

Open Access

https://doi.org/10.1074/jbc.ra119.011060

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Abstract

RAS genes are the most commonly mutated in human cancers and play critical roles in tumor initiation, progression, and drug resistance. Identification of targets that block RAS signaling is pivotal to develop therapies for RAS-related cancer. As RAS translocation to the plasma membrane (PM) is essential for its effective signal transduction, we devised a high-content screening assay to search for genes regulating KRAS membrane association. We found that the tyrosine phosphatase PTPN2 regulates the plasma membrane localization of KRAS. Knockdown of PTPN2 reduced the proliferation and promoted apoptosis in KRAS-dependent cancer cells, but not in KRAS-independent cells. Mechanistically, PTPN2 negatively regulates tyrosine phosphorylation of KRAS, which, in turn, affects the activation KRAS and its downstream signaling. Consistently, analysis of the TCGA database demonstrates that high expression of PTPN2 is significantly associated with poor prognosis of patients with KRAS-mutant pancreatic adenocarcinoma. These results indicate that PTPN2 is a key regulator of KRAS and may serve as a new target for therapy of KRAS-driven cancer.

Highlights

RAS proteins are small GTPases that regulate diverse cellular processes, including proliferation, differentiation, migration, apoptosis, and senescence [1]
To identify genes required for KRAS membrane trafficking, we developed an image-based screening assay that monitors the degree of KRASG12D membrane association (Fig. 1A)
We found that the majority of GFP-KRASG12D proteins are localized to the plasma membrane (PM) (Fig. 1B)

Summary

Introduction

RAS proteins are small GTPases that regulate diverse cellular processes, including proliferation, differentiation, migration, apoptosis, and senescence [1]. KRAS4A and KRAS4B result from an alternative splicing at the C terminus of the KRAS gene [2]. Inhibiting protein–protein interactions and KRAS localization are novel approaches to target mutant KRAS and block oncogenic KRAS signaling [14,15,16], the efficacy in clinical is still unknown. Targeting the KRAS effector signaling pathways could prove efficacious in treating tumors with KRAS mutations, as the inhibitors have entered clinical trials demonstrating promising clinical activity in KRAS mutant tumor [17, 18]. KRAS interacts with downstream effectors only when it associates with the plasma membrane (PM) [14, 22,23,24], so inhibition of KRAS localization is a valid therapeutic approach to block signal transmission by oncogenic KRAS. Inhibitors targeting FTase and GGTase in combination have been proved too toxic to be clinically useful [27]

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