Finally, while APOBEC3A expression was largely confined to IVL+ve/MKI67−ve (non-cycling) tumour cells, the correlation between APOBEC3A and IVL expression was weaker in the SCC datasets than in the normal tonsil epithelial cells, and in the UMAPs from the Southampton HNSCC dataset, APOBEC3A expression was apparent in IVL−ve cells, which also displayed high predicted GRHL3 activity (Fig. 5A). Here, IVL is linked to head and neck squamous cell carcinoma.