APOBEC3A and neoplasm: Since too few tumour cells in the scRNA-seq datasets from lung, breast and urothelial cancer that we analysed (Table EV1) expressed APOBEC3A to permit co-expression analysis, we examined APOBEC3A expression (Fig. EV2A), GRHL3 expression (Fig. EV2B) and GRHL3 activity (Fig. EV2C) in bulk RNA-seq data from The Cancer Genome Atlas (TCGA).