Abstract 1065: RASSF- 1A methylation in squamous cell carcinoma of the lower lip using pyrosequencing technique

Abstract

Background: Chronic exposure to UVB radiation can cause hypermethylation and silencing of the tumor suppressor gene RASSF-1A. The protein encoded by this gene has multiple important functions in cell cycle control. Objective: to investigate the clinical significance of the methylation profile of RASSF-1A and of its protein expression in lower lip squamous cell carcinoma (SCC). Methods: The demographic and clinical-pathological data of 87 patients with a confirmed diagnosis were collected from the medical records. DNA was extracted from paraffin-embedded tissue samples and treated with sodium bisulfite. 2ug of treated and intact DNA was submitted to PCR amplification using a specific primer targeting the RASSF-1A promoter segments 1 and 2. RASSF1A methylation was investigated by pyrosequencing; the complementary strand was synthesized automatically and the signal emitted during the reaction was detected with a camera and transformed into peaks on a pyrogram. Results: Lower lip SCC was more frequent in men than women, with a proportion of 2.4:1. The mean patient age was 63.3 years. Lymph node involvement was absent (N0) in 73 (83.1%) of cases and present (N+) in 14 (16.1%). In group N0, most patients (n = 49, 67.1%) were in an early clinical stage (CS I and II). Analysis of the methylation of RASSF1A_01 was possible in 29 of the SCC cases. Hypermethylation was observed in 15 (51.7%) cases, one (3.4%) of them being associated with metastasis to regional lymph nodes. Analysis of RASSF1A_02 was possible in 20 cases and hypermethylation was observed in only 9 (45.0%). No significant correlation was found between the clinical-pathological parameters (age, gender, clinical stage) and aberrant methylation of the promoter region studied (p>0.05). Conclusions: Hypermethylation of the two RASSF-1A segments studied was observed in approximately 50% of SCC cases, but was not correlated to clinicopathologic parameters. Citation Format: Estela Kaminagakura, Cláudia Coutinho-Camillo, Luciana Strieder, Danyel Perez, Fernando Soares, Kátia Oliveira, Luiz Paulo Kowalski. RASSF- 1A methylation in squamous cell carcinoma of the lower lip using pyrosequencing technique. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1065. doi:10.1158/1538-7445.AM2015-1065