MRC1 and mismatch repair cancer syndrome 1: Moreover, the mutational spectra we recorded do not show discernible contributions from MMR-associated COSMIC mutational signatures (i.e. SBS6, 14, 15, 20, 21, 26 and 44), supporting the view that the SBS11-like mutational spectra we observed were unlikely to reflect MMR deficiency in addition to alkylating agent exposure.