Estrogen Receptor Alpha Codon 594 G> A Polymorphism; A Risk Study for Early Onset Breast Cancer in Yogyakarta
ABSTRACT: Background: Early-onset breast cancer has a much poorer prognosis and lower survival rate. The pathogenesis of early onset breast cancer is influenced by both environmental and genetic factors. Studies on the association between ER-alpha codon 594 G>A polymorphism with a risk for breast cancer have been conducted on various populations in the world with contradicting results. This study has not yet been done in Indonesia. Purpose: To examine the proportion and correlation between ER-alpha codon 594 polymorphism (rs2228480) with a risk for early onset breast cancer in Yogyakarta. Method: Blood DNA were obtained from breast cancer patients registered at RS Dr. Sardjito in 2006-2012. Samples were chosen based on two age groups; <40 and > 55 years old. PCR-RFLP method was used to examine the G>A polymorphism. The association between the frequency of certain gene and allele variants with a risk for early onset breast cancer was analyzed using Chi-square, Z-test and Odds Ratio (OR). Result: Out of 206 samples, there are 116 (56.3%) with genotype G/G, 80 (38.8%) with genotype A/G and 10 (4.9%) with genotype A/A. Genotype and allele proportion between samples aged <40 years and >55 years showed no statistical differences (p = 0.982 and 0.642, respectively). Right-tailed Z-test (Alpha=5%) for difference in genotype and allele proportion between the two age groups gave Z values >1.645. OR for developing early onset breast cancer were 1.148 (95%CI = 0.315 to 4.180) for GG vs AA, 1.334 (95%CI = 0.754 to 2.362) for GG vs AG, and 1.202 (95%CI = 0.766 to 1.888) for allele G vs allele A. Conclusion: Genotype G/G was the most observed genotype variant, followed by genotype A/G and A/A. There was no statistically significant association between ER-alpha codon 594 risk allele A with a risk for early onset breast cancer in Yogyakarta.
