Musashi-2 (MSI2) regulates epidermal growth factor receptor (EGFR) expression and response to EGFR inhibitors in EGFR-mutated non-small cell lung cancer (NSCLC)

Petr Makhov,Nikolay Karnaukhov,Igor Bychkov,Hossein Borghaei,Mark Voloshin,Martin J Edelman ,Rushaniya Fazliyeva,Anna S Nikonova,Leonid Kharin ,Essel Dulaimi,Bulat Faezov,Alexander E Kudinov ,Oleg I Kit,Kathy Q Cai,Iuliia Topchu,Elena Mikhaylovna Frantsiyants ,Rohan Brebion,Ilya G Serebriiskii,Émmanuelle Nicolas ,Erica A Golemis,Eleanor Avril,Alexander Y Deneka ,Yanis Boumber

doi:10.1038/s41389-021-00317-y

Abstract

Non-small cell lung cancer (NSCLC) has limited treatment options. Expression of the RNA-binding protein (RBP) Musashi-2 (MSI2) is elevated in a subset of non-small cell lung cancer (NSCLC) tumors upon progression, and drives NSCLC metastasis. We evaluated the mechanism of MSI2 action in NSCLC to gain therapeutically useful insights. Reverse phase protein array (RPPA) analysis of MSI2-depleted versus control KrasLA1/+; Trp53R172HΔG/+ NSCLC cell lines identified EGFR as a MSI2-regulated protein. MSI2 control of EGFR expression and activity in an NSCLC cell line panel was studied using RT-PCR, Western blots, and RNA immunoprecipitation. Functional consequences of MSI2 depletion were explored for cell growth and response to EGFR-targeting drugs, in vitro and in vivo. Expression relationships were validated using human tissue microarrays. MSI2 depletion significantly reduced EGFR protein expression, phosphorylation, or both. Comparison of protein and mRNA expression indicated a post-transcriptional activity of MSI2 in control of steady state levels of EGFR. RNA immunoprecipitation analysis demonstrated that MSI2 directly binds to EGFR mRNA, and sequence analysis predicted MSI2 binding sites in the murine and human EGFR mRNAs. MSI2 depletion selectively impaired cell proliferation in NSCLC cell lines with activating mutations of EGFR (EGFRmut). Further, depletion of MSI2 in combination with EGFR inhibitors such as erlotinib, afatinib, and osimertinib selectively reduced the growth of EGFRmut NSCLC cells and xenografts. EGFR and MSI2 were significantly co-expressed in EGFRmut human NSCLCs. These results define MSI2 as a direct regulator of EGFR protein expression, and suggest inhibition of MSI2 could be of clinical value in EGFRmut NSCLC.

Highlights

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related deaths in the world[1]
Reverse Phase Protein Array (RPPA) analysis shows MSI2 depletion alters expression of ERBB family proteins in NSCLC cell lines We previously identified KrasLA1/+;P53R172HΔG/+ murine NSCLC cell lines expressing high (344SQ) versus low
As homodimers and heterodimers involving EGFR, ERBB2/HER2, and ERBB3/HER3 contribute to oncogenic signaling in in NSCLC3,9,12, and given that some antibodies used on Reverse phase protein array (RPPA) panels are not optimized[13], we further investigated MSI2 control of this ERBB protein family in detail using a panel of NSCLC cell models

Summary

Introduction

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related deaths in the world[1]. In EGFRmut NSCLC, tyrosine kinase inhibitors (TKIs) of EGFR have shown response rates of ~40–70%, with. Makhov et al Oncogenesis (2021)10:29 dramatic improvements in progression-free survival (PFS) in metastatic EGFRmut NSCLC patients compared to cytotoxic chemotherapy[3]. Five EGFR-targeting TKIs (gefitinib, erlotinib, afatinib, dacomitinib, and osimertinib) are FDA-approved frontline agents for patients with EGFR sensitizing mutations[3,4,5]. Amongst the contributing factors that influence which tumors respond to EGFR-targeted inhibitors are the type of EGFR mutation, as well as differences in the expression level of EGFR and of additional ERBB family members (ERBB2/ HER2, and ERBB3/HER3) with which EGFR can heterodimerize to signal. Given the variability of patient response to EGFR-targeted therapeutics, it is important to develop a clear understanding of which factors govern response

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