KRAS and colorectal carcinoma: Genetic and molecular mechanisms determining the ratio of high-affinity/low-affinity EGFR ligands, other than KRAS mutation status, should be elucidated through further comparative analyses of the therapeutic effects of GC1118 on CRC PDXs secreting mainly high- or low-affinity EGFR ligands using a larger panel of heterogenous CRC PDXs.