KRAS and colorectal neoplasm: We selected the KRAS wild type (WT) colorectal tumour cell line, LIM1215 as a model [26] and used AAV gene targeting to introduce one of three different oncogenic mutant KRAS alleles (enconding p.G12D, p.G12S and p.G12V) into the endogenous KRAS gene at position glycine 12 [27] (Fig 1A and S1 Fig).