Epigenetic Modification of Muscarinic Acetylcholine Receptors in Squamous Cell Carcinoma of the Head and Neck

Abstract

Background/aim: The five members of the mammalian muscarinic acetylcholine receptor family are encoded by the cholinergic receptor, muscarinic, 1-5 (CHRM1-5) genes. CHRM genes are incriminated in formation of various cancer types, but their roles in head and neck squamous cell carcinoma (HNSCC) are improperly understood. Aberrant epigenetic modifications of specific tumor-suppressor genes and oncogenes are known to promote cancer development. We aimed to analyze the connection between methylation of CHRM genes and HNSCC recurrence, with specific reference to human papillomavirus (HPV)-positive oropharyngeal carcinoma.

Materials and methods: We investigated the methylation state of CHRM1-CHRM5 genes expressed in 305 samples of primary HNSCCs by quantitative methylation-specific polymerase chain reaction. We explored associations between methylation of these genes and the clinicopathological characteristics of HNSCC (location of the tumor as well as recurrence) Results: We found 1.08±0.94 methylated genes per sample (range=0-5), with promoters of CHRM1-5 genes methylated in 85.9%, 47.5%, 10.2%, 17.7%, and 19.3%, respectively, of the evaluated samples. Methylation levels of CHRM2 were significantly raised in HNSCC samples compared to corresponding normal tissues (p<0.001). Although there was no significance of tumor location, analysis by Kaplan-Meier estimate and multivariate Cox proportional hazard methods showed that methylated CHRM2 was significantly associated with increased recurrence of HNSCC with HPV-positive oropharyngeal cancer.

Conclusion: CHRM methylation status is associated with HNSCC pathogenesis.

Keywords: G protein-coupled receptor; Muscarinic acetylcholine receptors; Q-MSP; epigenetic markers; oropharyngeal cancer.