NRAS and colorectal cancer: No cell lines in the four groups possessed mutations in the homologous NRAS gene, but 2 cell lines from the quadruple mutated group had homo-deletions of the NRAS locus at chromosome 1p13.2, an alteration that is rarely observed in colorectal cancer patient samples, with a prevalence of 0.7% in the colorectal cohort from TCGA.