Gene expression changes associated with acquired resistance to anti-EGFR therapy (cetuximab) in colorectal cancer cells

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 thereby leading to clinical relapse. Understanding molecular mechanisms that support acquired resistance to anti-EGFR targeted therapy in mCRC is therefore clinically relevant and key to improving patient outcomes. Here, we observe distinct metabolic changes between cetuximab-resistant CRC cell populations, with in particular an increased glycolytic activity in KRAS-mutant cetuximab-resistant LIM1215 but not in KRAS-amplified resistant DiFi cells. We show that cetuximab-resistant LIM1215 cells have the capacity to recycle glycolysis-derived lactate to sustain their growth capacity. This is associated with an upregulation of the lactate importer MCT1 at both transcript and protein levels. Pharmacological inhibition of MCT1, with AR-C155858, reduces the uptake and oxidation of lactate and impairs growth capacity in cetuximab-resistant LIM1215 cells. This study identifies MCT1-dependent lactate utilization as a clinically actionable, metabolic vulnerability to overcome KRAS-mutant-mediated acquired resistance to anti-EGFR therapy in CRC. To study the metabolic adaptation of CRC cells upon acquired resistance to cetuximab treatment, we used two human colon cancer cell lines LIM1215 and DiFi, initially cetuximab-sensitive (denoted as -S), and for which populations with acquired resistance (-R1 and -R2) had been previously established upon chronic exposure for several months with the drug (Misale et al Nature 2012). While DiFi-R cells harbored EGFR gene copy number reduction and KRAS gene amplification, LIM1215-R cells were reported to display KRAS activating mutations. We then carried out gene expression profiling analysis using RNA-seq data obtained from cetuximab-resistant (-R1 and -R2) and cetuximab-sensitive (-S) DiFi and LIM1215 CRC cells.