HER-2 [Ile655Val] polymorphism in association with breast cancer risk: a population-based case-control study in Slovakia

Abstract

Breast cancer belongs to the most frequent types of cancer affecting women and it occurs at any age. Around 1600-1800 women are getting ill annually in the Slovak republic. One of the most important factors in connection with cancer genesis refers to changes in specific genes. HER-2 proto-oncogene belongs to low penetrating genes, which increase susceptibility to breast cancer genesis. Clinical studies demonstrated an association between polymorphism at codon 655 of this gene and increased risk for breast cancer development. The aim of this case-control based prospective study was to determine the distribution of HER-2 genotype and its association with risk factors of breast cancer in the population of women in Slovak republic. HER-2 genotypes were determined with PCR-RFLP method. The DNA was isolated from white blood cell nuclei. The frequency of Val allele in the cancer group was 29.79% and was higher than in the control group 15.84% (p<0.05). The presence of the heterozygote (Ile/Val) genotype was identified in 46.81% of patients in the case group and in 28.33% in healthy individuals, and the homozygote (Val/Val) genotype in 6.38% and 1.67, respectively (p<0.01). The risk of breast cancer development for carriers of one valine (Val) allele in genotype was two-times lower (OR=2.47) than for carriers of two Val alleles (OR=5.73) (p<0.05). Risk of cancer genesis for Val allele carriers was higher in multiparas (OR=2.90), among women with positive family history of breast cancer (OR=5.0), BMI>24 (kg/m2), and late menopause (OR=1.5). Contraceptives in anamnesis contrariwise showed tend to decrease the risk in Val allele carriers (OR=0.3). In conclusion, this study revealed relatively high frequency of the Val allele among the women population of the Slovak republic. Ile655Val polymorphism of HER-2 gene was associated with a statistically significantly increased risk of breast cancer all above in homozygotes for Val allele.