Differential expression of nicotinamide N-methyltransferase in primary and recurrent ameloblastomas and odontogenic keratocysts

Background: Odontogenic tumours are a group of rare heterogeneous diseases that range from hamartomatous tissue proliferations to benign and malignant neoplasms. Recurrences can occur after 10 years, so long-term clinical and radiological follow-up is required. The study of the molecular mechanisms involved in the development of these lesions is necessary to identify new prognostic markers. In this study, we evaluate the possible role of nicotinamide N-methyltransferase (NNMT) in ameloblastomas (AM) and odontogenic keratocysts (OKC). Materials and methods: A total of 105 surgical specimens of primary and recurrent lesions were obtained from 55 patients (25 AM, 30 OKC). In particular, 50 AMs (25 primary, 25 recurrences) and 55 OKCs (30 primary, 25 recurrences) were retrieved. We carried out immunohistochemical analyses to evaluate the cytoplasmic expression of NNMT, measuring the percentage of positive cells and the value of NNMT expression intensity. Results: NNMT expression was significantly higher in recurrent than primary AMs (P =.0430). This result was confirmed by staining intensity, showing more cases with moderate/intense staining in recurrent AMs (P =.0470). NNMT expression was significantly lower in recurrent than primary OKC (P =.0014). Staining intensity showed more cases with moderate/intense staining in primary OKCs (P =.0276). Conclusions: This report is the first to evaluate NNMT expression in odontogenic lesions and to demonstrate a differential expression in recurrent AMs and OKCs, suggesting that there is potential for use of NNMT as prognostic marker. © 2020 Stichting European Society for Clinical Investigation Journal Foundation. Published by John Wiley & Sons Ltd