Association study of LMP-1 expression and promoter methylation status of tumor suppressor gene RASSF1A in nasopharyngeal carcinoma

Abstract

Nasopharyngeal carcinoma (NPC) is a cancer originating fromnasopharyngeal epithelial tissue. Genetic susceptibility,
exposure to carcinogens, and Epstein-Barr virus (EBV) infection are the main factors in NPC development. Latent
membrane protein 1 (LMP-1) is a product of EBV genome, which is able to interact with various intracellular signaling
pathways that leads to expression of many proteins, e.g DNA methyltransferase. The increase expression of DNA
methyltransferase could induce hypermetylation of tumor suppressor genes (TSG). Ras-association domain family
1A (RASSF1A) is one of TSG that frequently hypermethylated in NPC cases. The aim of this study is to determine
the association between LMP-1 expression and promoter methylation status of RASSF1A in NPC patients. The
research subjects were 36 NPC patients of the Dr. Sardjito Hospital, Yogyakarta, Indonesia. Latent membrane
protein 1was stained immunohistochemically using monoclonal antibody OT21C. Ras-association domain family 1A
methylation statuswas examined by methylation specific PCR (MSP) of DNA isolated fromnasopharyngeal brushing.
Chi-square analysis was conducted to examine the association between LMP-1 expression and methylation status of
RASSF1A with 95%confidence interval. Latent membrane protein 1 was expressed in 44.4%subjects. The scores
of LMP-1 expression were ranged from 0-8 (average of 1.56±2.16). Ras-association domain family 1A methylated
in 66.7% of subjects. Statistical analysis showed that there was a relationship between LMP-1 expression and
methylation status of RASSF1A (p<0.05). Statistical analysis also showed association between LMP-1 expression
score and RASSF1A methylation status (p<0.05). It can be concluded that there was an association between the
expression of LMP-1 and RASSF1A methylation status in NPC patients.
Keywords: LMP1 - RASSF1A – NPC – hypermethylation - DNA methyltransferase - methylation specific PCR