DNA methylation analysis from oral brushing reveals a field cancerization effect in proliferative verrucous leukoplakia.

Objectives: The aim of the present study was to analyze the methylation status in patients who presented with an Oral Squamous Cell Carcinoma (OSCC) concomitantly with multifocal Proliferative Verrucous Leukoplakia (PVL)(PVL-OSCC).

Methods: Nine patients with OSCC and concomitant PVL lesions were selected. Two brushing samples were collected simultaneously from OSCC and PVL lesions in contralateral mucosa from each patient. 15 genes (272 CpGs) were used to compare methylation profiles of PVL-OSCC and paired OSCC. CpGs with a methylation level superimposable between PVL-OSCC and contralateral OSCC were selected for a comparative analysis between PVL-OSCC, 8 PVL patients with no history of OSCC (PVL) and 23 healthy donors. Samples were also tested using an algorithm that was recently validated for epigenetic alterations in OSCC.

Results: 220/272 CpGs islands (80%) showed a superimposable methylation level in OSCC and in PVL-OSCC. 10 genes (88 CpGs) and in particular and 100% of the studied CpGs) were able to stratify PVL-OSCC from PVL and healthy donors. 3/4 (75%) PVL-OSCC patients with a "positive" algorithm score developed second neoplastic events compared to only 1/5 (20%) patients with a "negative" score.

Conclusions: The present study provides evidence that PVL shares an aberrant methylation profile with contralateral OSCC. In agreement with the theory of field cancerization, our data point towards the potential role of epigenetics in patients at risk of developing multiple neoplastic events.