EGFR blockade reverts resistance to KRAS G12C inhibition in colorectal cancer

Most KRAS G12C mutant non-small cell lung cancer (NSCLC) patients experience clinical benefit from selective KRAS G12C inhibition, while patients with colorectal cancer (CRC) bearing the same mutation rarely respond. To investigate the cause of the limited efficacy of KRAS G12C inhibitors in CRC, we examined the effects of AMG510 in KRAS G12C CRC cell lines. Unlike NSCLC cell lines, KRAS G12C CRC models have high basal receptor tyrosine kinase (RTK) activation and are responsive to growth factor stimulation. In CRC lines, KRAS G12C inhibition induces higher phospho-ERK rebound than in NSCLC cells. Although upstream activation of several RTKs interferes with KRAS G12C blockade, we identify EGFR signaling as the dominant mechanism of CRC resistance to KRAS G12C inhibitors. The combinatorial targeting of EGFR and KRAS G12C is highly effective in CRC cells, patient-derived organoids and xenografts, suggesting a novel therapeutic strategy to treat KRAS G12C CRC patients.