DNA methylation and copy number alterations in the progression of HPV-associated high-grade vulvar intraepithelial lesion

Abstract

Human papillomavirus (HPV)-associated high-grade vulvar intraepithelial lesion (HSIL) is a precursor of vulvar squamous cell carcinoma (VSCC). Because of the 8% cancer risk, many vulvar HSIL patients undergo aggressive and mutilating treatments. Characterizing HSIL by their progression risk can help individualize treatment strategies. Accordingly, copy number alterations (CNAs) and DNA methylation have been identified as biomarkers for cancer risk stratification of HSIL. Here, we assessed their potential correlation, and relation to HPV16 (sub)lineages and progression to vulvar cancer. Eighty-two vulvar formalin-fixed paraffin-embedded (FFPE) samples, including controls, HSIL, HSIL adjacent to VSCC and VSCC, with previously determined DNA methylation profiles, were analysed for CNAs using mFAST-SeqS. Genome-wide z-scores were calculated to determine overall aneuploidy (aneuploidy scores), and compared to the methylation levels and status of marker panel ZNF582/SST/miR124-2. For 52 HPV16-positive cases, HPV (sub)lineages were determined by Sanger sequencing. HPV16 lineage A was predominant (86.4%), followed equally by lineages B, C, and D. Frequent chromosomal alterations included chr1pq, chr3q, chr9q gains, and chr2q, chr4q losses. Median aneuploidy scores increased across disease categories, from 0 in controls, to 3 in HSIL, 16 in HSIL adjacent to VSCC and 29 in VSCC. A positive relationship between aneuploidy scores and DNA methylation levels was found (ρ = 0.61, Spearman's rank correlation test). Aneuploidy scores were significantly higher in methylation-positive samples (p < .001). In conclusion, we showed that DNA methylation and CNAs both rise with increasing severity of disease, indicating their prognostic value for cancer risk stratification of HSIL, while no relation to HPV16 (sub)lineages was found.