By deep sequencing of the parental cell lines, they uncovered that 0.2% of the parental Lim1215 CRC cells harboured the mutant KRAS G12D genotype which eventually became predominant, leading the authors to conclude that cetuximab exerted a selection advantage to the small proportion of cells that were resistant, and was able to expand and repopulate the tumour when sensitive cells were killed. The gene discussed is KRAS; the disease is neoplasm.