Methylation of CpG sites in the upstream regulatory region, physical status and mRNA expression of HPV-6 in adult-onset laryngeal papilloma.

Zeyi Deng,Tao Zhang,Hiroyuki Maeda,Chunlin Zhang,Taro Ikegami,Sen Matayoshi,Takayuki Uehara,Akira Ganaha,Mikio Suzuki,Asanori Kiyuna

doi:10.18632/oncotarget.19898

Abstract

The methylation status of HPV-6 upstream regulatory region (URR) in adult-onset laryngeal papillomatosis (AO-LP) remains unclear. The purpose of this study was to investigate the methylation status of URR and the physical status of HPV-6, as well as the dynamic variations of viral load and mRNA expression in AO-LP. We examined 18 specimens from 11 patients with AO-LP by real-time polymerase chain reaction (PCR), bisulfite-sequencing PCR, and amplification of papilloma oncogene transcripts. HPV-6 was identified in 9 of 11 patients (81.8%), and all the 15 specimens derived from 9 HPV-6-positive cases contained only episomal HPV-6 transcripts with intact E2. Three HPV-6-positive patients developed recurrent lesions, and HPV-6 copy numbers and mRNA expression decreased after surgical treatment. Among the 96 CpG sites (16/case), 67 (69.8%) were unmethylated, while 23 (30.2%) were heterogeneous (≥ 1 methylated CpG clone). High viral loads and episomal status of HPV-6 were frequently observed in AO-LP; thus, persistent E6/E7 mRNA expression of LR-HPV-6 may be associated with AO-LP recurrences. Hypomethylation and scattered patterns of methylated CpGs at the URR of HPV-6 were identified in AO-LP.

Highlights

Human papillomaviruses (HPVs) are small icosahedral viruses containing 8 or 9 genes on circular double-stranded DNA
High viral loads and episomal status of HPV-6 were frequently observed in adult-onset laryngeal papillomatosis (AO-LP); persistent E6/E7 mRNA expression of low-risk human papillomaviruses (LR-HPVs)-6 may be associated with AO-LP recurrences
We studied only HPV-6 because this virus is a unique subtype found in AO-LP populations

Summary

Introduction

Human papillomaviruses (HPVs) are small icosahedral viruses containing 8 or 9 genes on circular double-stranded DNA. More than 150 types have been identified to date. HPV infection can stimulate benign tumors, promote oncogenic changes, or be asymptomatic in epithelial cells [1]. Adult-onset laryngeal papillomatosis (AO-LP), usually a benign tumor of the larynx, is induced by low-risk human papillomaviruses (LR-HPVs), especially HPV-6 and -11 [2, 3]. AO-LP is characterized by recurrences and warty exophytic lesions in the larynx, but can spread to the whole respiratory tract including the lungs in up to 20% of adult patients [2, 4]. The recurrent nature of AO-LP could be due to persistent viral reservoirs and activation of asymptomatic HPV infections [5]. But this has been reported in less than 3% of cases [6, 7]

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