[Human Papillomavirus Carcinogenesis Mediated by APOBEC Mutagenesis]

Persistent infection with oncogenic human papillomaviruses (HPVs) is necessary for the development of cervical cancer, although the accumulation of somatic mutations in the host genome is also required for the generation of invasive cervical cancer. Recent studies have demonstrated concomitant genetic changes in the HPV genome; however, their relevance to cervical carcinogenesis is poorly understood. Here we review our recent study investigating the within-host genetic diversity of HPV and its relationship with cervical cancer progression through deep sequencing analyses of viral whole-genome sequences in clinical specimens. Intriguingly, HPV genomes within individual clinical samples show an astonishingly high level of nucleotide variation across all histological grades of cervical lesions. Among the various substitution patterns, C-to-T and C-to-A substitutions are the predominant changes observed in the HPV genomes. Analysis of the trinucleotide context for substituted bases reveals that TpCpN (N is any nucleotide), which is a preferred target sequence for the cellular apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like (APOBEC) proteins, is the major target for C-to-T substitutions in the HPV genomes. These mutational signature analyses strongly imply that within-host HPV variations are mostly generated through APOBEC-mediated mutagenesis. Because the HPV oncogenes E6 and E7 harbor APOBEC-related mutations, we propose a potential role for APOBEC-mediated mutagenesis in cervical carcinogenesis.