Similarly, while spatial transcriptomics and immunohistochemistry of sections from these HNSCCs revealed widespread APOBEC3B expression (particularly in HPV +ve cases, as expected), APOBEC3A was not expressed in all cases and in those tumours where expression was observed, it was restricted to areas of high GRHL3 activity (Fig. 5). Here, GRHL3 is linked to neoplasm.