Proteomic Profiling of BRAFV600E Mutant Colon Cancer Cells Reveals the Involvement of Nucleophosmin/c-Myc Axis in Modulating the Response and Resistance to BRAF Inhibition by Vemurafenib.

Petra Grbčić,Sandra Kraljević Pavelić,Tania Gamberi,Mirela Sedić,Dora Fučkar Čupić

doi:10.3390/ijms22126174

Petra Grbčić, Sandra Kraljević Pavelić + Show 3 more

Open Access

https://doi.org/10.3390/ijms22126174

Copy DOI

Abstract

BRAFV600E mutations are found in approximately 10% of colorectal cancer patients and are associated with worse prognosis and poor outcomes with systemic therapies. The aim of this study was to identify novel druggable features of BRAFV600E-mutated colon cancer (CC) cells associated with the response and resistance to BRAFV600E inhibitor vemurafenib. Towards this aim, we carried out global proteomic profiling of BRAFV600E mutant vs. KRAS mutant/BRAF wild-type and double wild-type KRAS/BRAF CC cells followed by bioinformatics analyses. Validation of selected proteomic features was performed by immunohistochemistry and in silico using the TCGA database. We reveal an increased abundance and activity of nucleophosmin (NPM1) in BRAFV600E-mutated CC in vitro, in silico and in tumor tissues from colon adenocarcinoma patients and demonstrate the roles of NPM1 and its interaction partner c-Myc in conveying the resistance to vemurafenib. Pharmacological inhibition of NPM1 effectively restored the sensitivity of vemurafenib-resistant BRAF-mutated CC cells by down-regulating c-Myc expression and activity and consequently suppressing its transcriptional targets RanBP1 and phosphoserine phosphatase that regulate centrosome duplication and serine biosynthesis, respectively. Altogether, findings from this study suggest that the NPM1/c-Myc axis could represent a promising therapeutic target to thwart resistance to vemurafenib in BRAF-mutated CC.

Highlights

BRAFV600E mutations are found in approximately 10% of colorectal cancer (CRC) patients and are associated with sustained cell proliferation, diminished apoptosis and acquired resistance to standard and targeted chemotherapies [1]
Treatment with single-agent BRAFV600E inhibitor vemurafenib (PLX4032) resulted in promising response rates in metastatic melanoma patients harboring the BRAFV600E mutation, clinically meaningful activity was not achieved in BRAF mutant metastatic CRC patients, which implies that the BRAFV600E-regulated response and resistance to therapy mirror tissue- and cancer-type specific biological contexts defined by the BRAFV600E mutation
We described up-regulated proteomic features that could be associated with the BRAFV600E mutation in colon cancer cells

Summary

Introduction

BRAFV600E mutations are found in approximately 10% of colorectal cancer (CRC) patients and are associated with sustained cell proliferation, diminished apoptosis and acquired resistance to standard and targeted chemotherapies [1]. Treatment with single-agent BRAFV600E inhibitor vemurafenib (PLX4032) resulted in promising response rates in metastatic melanoma patients harboring the BRAFV600E mutation, clinically meaningful activity was not achieved in BRAF mutant metastatic CRC patients, which implies that the BRAFV600E-regulated response and resistance to therapy mirror tissue- and cancer-type specific biological contexts defined by the BRAFV600E mutation. The heterogeneous clinical response to targeted therapies observed in BRAFV600E mutant CRC patients has spurred investigation into the molecular basis underlying these differences, which has led to the discovery of two gene expression-based subgroups of BRAFV600E-mutated CRC, one exerting KRAS/AKT pathway activation, mTOR/4EBP deregulation and epithelial–mesenchymal transition (EMT), and the other showing dysregulation of the cell cycle [3]. The same study indicated that these two subtypes have different sensitivities in silico to targeted chemotherapy drugs including BRAF and MEK inhibitors, reflecting their observed molecular differences

Objectives

Methods

Findings

Conclusion