EVALUATING THE METHYLATION STATUS OF RB1 GENE PATIENTS WITH RETINOBLASTOMA

Abstract

OBJECTIVES: The most frequently diagnosed malignant ocular tumor of infancy and childhood is Retinoblastoma. Due to the mutation on the q14 on chromosome 13 causes the retinoblastoma. There are two types of basic gene mutations: genetic and sporadic. This cancer is initiated by RB1 mutation, responsible for the cell cycle regulation and genome stability in the cells of the retina in children under 5 years old. The retinoblastoma comprises about 40% inherited mutations, 10% of germline mutations of RB1 inherited from an affected parent, and 30% from de-novo germline mutations. MATERIAL&METHODS: Methylation of the RB1 gene on promoter region is unknown. The results obtained by MLPA analysis and sequence analysis were investigated for RB1 gene methylation in patients without RB1 mutation. The methylation determination is done with OneStep qMethyl-PCR Kit using a Real-Time PCR system. Methylation changes were investigated in peripheral blood samples of 60 patients with retinoblastoma, 18% of the patients (11/60) had bilateral and 82% of patients (49/60) had unilateral disease and 52 healthy controls. RESULTS: The mean methylation levels of 60 retinoblastoma patients and 52 healthy controls were 35% and 34%, respectively. Mann Whitney U test was compared between the patient and healthy controls and no statistically significant difference was detected between the two groups (p = 0.882). CONCLUSIONS: The promoter methylation levels in RB1 gene patients having familial history was believed to be large deletion and duplication and small indel absence mutations in the RB1 gene are not effective especially in the etiology of heritable retinoblastoma. Keywords: Retinoblastoma, RB1 gene mutation, Promoter Methylation