Clonal biases dictate availability of colonic cancer driver mutations for transformation

Aged normal tissues harbour cancer mutations predisposing to transformation. However, previous studies of human colon have not allowed a comparison of the prevalence and behaviours of different pro-oncogenic events. Here, having detected cancer driver mutations in histologically normal FFPE tissue using targeted amplicon sequencing, we perform spatial transcriptomics to investigate whether monoallelic cancer driver clones can be phenotypically profiled in normal tissue. We found that KRAS mutant clones are associated with a profound shift in their transcriptome and were able to create a signature of 628 genes. The results highlighted phenotypic heterogeneity in KRAS mutant clones of the same genotype, with mixed lineage presentation seen in a proportion of them, a state that has been linked with increased risk of transformation in other organs. REG4 was also identified as a surrogate protein marker of KRAS mutant clones, the use of which could be further validated in a clinical setting for patient stratification. Overall design: Human FFPE samples of normal colon tissue with previously identified cancer driver mutations (based on targeted-amplicon sequencing) were subjected to 10X Visium. Targeted-amplicon sequecing had allowed the spatial localisation of the mutant areas, so only these parts of the tissue, togetther with some adjacent normal, were subjected to sequencing.