Somatic whole exome sequencing of colorectal carcinoma in young patients from sub-Saharan Africa reveals novel insights

Colorectal carcinoma (CRC) is a frequent cause of morbidity and mortality in sub-Saharan Africa. The incidence of early-onset, microsatellite stable (MSS) CRC is on the rise, and the tumour biology of these lesions is poorly categorised. Preliminary data from one centre in Nigeria found differences in the frequencies of mutations in driver genes and altered signalling pathways. We sought to investigate potential alternative driver genes and signalling pathways by whole exome sequencing. Eighty-three cases passed quality control filters and were included in the analysis (77 MSS, 4 microsatellite instability-high, and 2 POLE mutant). APC, TP53, and KRAS were among the most frequently mutated driver genes, although at a lower frequency than expected. BRAF V600E mutations were absent in our cohort. Although there were differences in the frequencies of mutations in the major driver genes, the frequencies of oncogenic pathway alterations were found to be similar. FAT4 (26%) and TET2 (15%) emerged as important mutated driver genes and potential therapeutic targets for further investigation. We have highlighted distinct differences in driver gene mutations in our cohort of young CRC from sub-Saharan Africa and have identified FAT4 and TET2 as potential drivers that are more common and are potential therapeutic targets.