RARβ2 suppression in head and neck squamous cell carcinoma correlates with site, histology and age

Abstract

Abstract. Retinoids as important growth and differentiation regulating agents have a potential role in the chemoprevention of head and neck squamous cell carcinoma (HNSCC). Despite the promising preclinical and early clinical findings, limitations of application are raised by intrinsic resistance acquired during carcinogenesis. Retinoic acid receptor ß2 (RARß2) is one of the proximate mediators of retinoid signalling and its expression is often diminished in early stages of head and neck carcinogenesis. One form of retinoid resistance has been associated with the methylation-induced silencing of the RARß gene. We studied primary HNSCC samples of different anatomical sites in respect of methylation, expression and allelic loss of RARß gene. A strong correlation (p<0.01) was found between hypermethylation and reduced expression of RARß2, however the allelic loss at 3p24, the locus of RARß, did not considerably influence its mRNA level. Hypopharynx tumors showed significantly lower hypermethylation (p<0.05) and higher mRNA expression levels of RARß2 compared to the tumors located at other sites of the head and neck. We could also provide evidence that poorly differentiated grade 3 tumors had significantly higher RARß2 expression and lower methylation levels (p<0.05) than better differentiated grade 1 and grade 2 tumors. In addition, we found a good correlation between the methylation degree of the RARß2 promoter and the ages of patients. Collectively, our results suggest that evaluation of several factors such as tumor location, age, histology and methylation state of the RARß gene might contribute to the selection of patients for retinoid-based chemoprevention.

Methylation in oral cancer and pre-cancerous lesions (Review)

“…furthermore, the prevalence was reported to increase with a higher grade of dysplasia (23). olazs et al (31), among others, analyzed the effects of hypermethylation and loss of heterogeneity in genes that transcribe rArβ 2 receptors, studying their role in retinoid therapy and chemoprevention. In their study of 89 primary head and neck tumours, methylation was the major cause of suppression of these receptors and was found in the tumour and as an early event in the carcinogenesis.…”

“…In their study of 89 primary head and neck tumours, methylation was the major cause of suppression of these receptors and was found in the tumour and as an early event in the carcinogenesis. rArβ 2 methylation was not associated with tumour localization, stage or metastasis but was related to higher age, apparently due to the longer contact time between carcinogenic elements and mucosa (31). It also appears to be significantly related to tumours with an aggressive phenotype and to a poor survival prognosis (29).…”

“…some authors use formalin-fixed and paraffinembedded tissue for pathology and immunohistochemistry studies, cutting it into 5-µm sections, which are kept in gelatine capsules for haematoxylin-eosin staining (26,28,36). Other authors freeze samples at -80˚C and cut them with a microtome (16,(18)(19)(20)(21)(22)27,31,38). others have used both procedures in the same study, freezing tissue samples of normal mucosa, mild dysplasia, severe dysplasia and OSCC at -70˚C and cutting them into 5-µm sections (haematoxylin-eosin staining) and fixing samples from healthy patients with alcohol and embedding them in paraffin (23).…”

Expression of the tumor suppressor gene hypermethylated in cancer 1 in laryngeal carcinoma

“…According to Smigiel et al (17), CDKN2A hypermethylation is reflected by a high grade of histological differentiation of the tumor (G3) (17). Olasz et al (18) reported that RARβ2 hypermethylation is observed in patients with well-differentiated lesions.…”

“…Improper methylation status of the following genes has been identified thus far in laryngeal cancer: Retinoic acid receptor β (RARβ), death-associated protein kinase (DAPK), cyclin-dependent kinase inhibitor 2A (CDKN2A), MGMT, RASSF1A, fragile histidine triad, chromodomain-helicase-DNA-binding protein 5, cellular retinol binding protein 1 and HIC1 (12)(13)(14)(15)(16)(17)(18)(19). The majority of the studies reported certain correlations between the clinical course of the disease and the molecular changes identified.…”