Metabolic characterization of colorectal cancer cells upon acquired resistance to anti-EGFR therapy

Details

Supervisors

Corbet, Cyril

Faculty

Faculté de pharmacie et des sciences biomédicales

Degree label

Master [120] en sciences biomédicales, à finalité approfondie

Abstract

Colorectal cancer (CRC) is the third most common cancer and the second leading cause of cancer death worldwide. Despite the implementation of personalized medicine, patients with metastatic CRC (mCRC) still have a dismal overall survival due to the frequent occurrence of acquired resistance mechanisms. Indeed, for mCRC patients who can be initially treated with anti-EGFR (epidermal growth factor receptor) targeted therapies (cetuximab), the clinical benefit is often temporary, and resistance invariably ensues, thereby leading to clinical relapse. Understanding molecular mechanisms that support acquired resistance to cetuximab in mCRC is therefore clinically relevant and key to improving patient outcomes. The general aim of my Master thesis was to characterize the metabolic alterations of CRC cells upon acquired resistance to cetuximab. After validation of the cetuximab-resistant DiFi and LIM1215 CRC cell models, a metabolic profiling was initiated via the dosage of extracellular and intracellular metabolites, 13C metabolic tracing, real-time bioenergetics analysis, viability assays with specific metabolic inhibitors, RT-qPCR, and western blot. We observed distinct metabolic changes between cetuximab-resistant DiFi and LIM1215 cell populations, with in particular an increased glycolytic activity in KRAS-mutant cetuximab-resistant LIM1215 but not in KRAS-amplified resistant DiFi cells. Interestingly, we showed that these cells had the capacity to recycle glycolysis-derived lactate to sustain their growth. This was associated with an upregulation of the lactate importer MCT1 at both transcript and protein levels. Pharmacological inhibition of MCT1, with either AR- C155858 or syrosingopine, reduced the uptake and oxidation of lactate in cetuximab- resistant LIM1215 cells. Transcriptomic analyses also identified PADI2 gene, encoding the peptidyl arginine deiminase 2, as being consistently downregulated in cetuximab-resistant CRC cells, and this was confirmed at the protein level. This protein may be related to the control of beta-catenin expression via a citrullination-based post-translational modification. All these results reveal new potential metabolism-related therapeutic targets that could be considered to overcome acquired resistance to cetuximab in mCRC.