Whole exome sequencing identifies mTOR and KEAP1 as potential targets for radiosensitization of HNSCC cells refractory to EGFR and β1 integrin inhibition.

Erik Klapproth,Falk Zakrzewski,Ellen Dickreuter,Andreas Petzold,Barbara Klink,Nils Cordes,Evelin Schröck,Andreas Dahl,Michael Seifert

doi:10.18632/oncotarget.24266

Abstract

Intrinsic and acquired resistances are major obstacles in cancer therapy. Genetic characterization is commonly used to identify predictive or prognostic biomarker signatures and potential cancer targets in samples from therapy-naïve patients. By far less common are such investigations to identify specific, predictive and/or prognostic gene signatures in patients or cancer cells refractory to a specific molecular-targeted intervention. This, however, might have a great value to foster the development of tailored, personalized cancer therapy. Based on our identification of a differential radiosensitization by single and combined β1 integrin (AIIB2) and EGFR (Cetuximab) targeting in more physiological, three-dimensional head and neck squamous cell carcinoma (HNSCC) cell cultures, we performed comparative whole exome sequencing, phosphoproteome analyses and RNAi knockdown screens in responder and non-responder cell lines. We found a higher rate of gene mutations with putative protein-changing characteristics in non-responders and different mutational profiles of responders and non-responders. These profiles allow stratification of HNSCC patients and identification of potential targets to address treatment resistance. Consecutively, pharmacological inhibition of mTOR and KEAP1 effectively diminished non-responder insusceptibility to β1 integrin and EGFR targeting for radiosensitization. Our data pinpoint the added value of genetic biomarker identification after selection for cancer subgroup responsiveness to targeted therapies.

Highlights

Intrinsic and acquired resistance are major obstacles in cancer therapy [1,2,3]
Pharmacological inhibition of mechanistic target of rapamycin (mTOR) and Kelch Like ECH Associated Protein 1 (KEAP1) effectively diminished non-responder insusceptibility to β1 integrin and EGFR targeting for radiosensitization
We found a higher rate of gene mutations with putative protein-changing characteristics in non-responders, mutational profiles of responders and non-responders that allow stratification of head and neck squamous cell carcinoma (HNSCC) patients, and pharmacological inhibition of Kelch Like ECH Associated Protein 1 (KEAP1) and mechanistic target of rapamycin to effectively diminish non-responder insusceptibility to β1 integrin and EGFR targeting for radiosensitization

Summary

Introduction

Intrinsic and acquired resistance are major obstacles in cancer therapy [1,2,3]. The plethora of factors creating this resistance spans from gene mutations, over epigenetic alterations to microenvironmental cues. While some successes document the feasibility and translatability of these approaches, similar investigations for identifying biomarker signatures in patients and cancer cells refractory to a specific molecular-targeted intervention have been rarely accomplished [7, 8]. Such experimental approaches might have a great added value to discriminate between responding and non-responding patients before start of treatment or uncover treatment failure early after start of treatment. The former could be made feasible by exposing tumor biopsies to the treatment of choice and monitor a particular marker or endpoint over a reasonable, clinically accountable short period of time

Methods

Results

Conclusion