Characterization of Epigenomic Alterations in HPV16+ Head and Neck Squamous Cell Carcinomas

Epigenetic changes associated with human papillomavirus (HPV)-driven tumors have been described; however, HPV type-specific alterations are less well understood. We sought to compare HPV16-specific methylation changes with those in virus-unassociated head and neck squamous cell carcinomas (HNSCC).

Within The Cancer Genome Atlas, 59 HPV16+ HNSCC, 238 nonviral HNSCC (no detectable HPV or other viruses), and 50 normal head and neck tissues were evaluated. Significant differentially methylated regions (DMR) were selected, and key associated genes were identified. Partial least squares models were generated to predict HPV16 status in additional independent samples.

HPV infection in HNSCC is associated with type-specific methylomic profiles. Multiple significant DMRs were identified between HPV16+, nonviral, and normal samples. The most significant differentially methylated genes, SYCP2, MSX2, HLTF, PITX2, and GRAMD4, demonstrated HPV16-associated methylation patterns with corresponding alterations in gene expression. Phylogenetically related HPV types (alpha-9 species; HPV31, HPV33, and HPV35) demonstrated a similar methylation profile to that of HPV16 but differed from those seen in other types, such as HPV18 and 45 (alpha-7).

HNSCC linked to HPV16 and types from the same alpha species are associated with a distinct methylation profile. This HPV16-associated methylation pattern is also detected in cervical cancer and testicular germ cell tumors. We present insights into both shared and unique methylation alterations associated with HPV16+ tumors and may have implications for understanding the clinical behavior of HPV-associated HNSCC.

HPV type-specific methylomic changes may contribute to understanding biologic mechanisms underlying differences in clinical behavior among different HPV+ and HPV- HNSCC.