We searched for genetics polymorphism in promoter region of ERα (А, В, С), ERβ, PR (А, В), Cx26 genes in breast cancer patients using direct DNA sequencing. The results demonstrated that ERαВ, ERαС, PRА, PRВ, Cx26 have sequence variation neither among genotypes, nor among different samples (cancer and normal tissue) of the same patient; these findings are in accordance with previously published observations.
A single nucleotide mutation was detected in the promoter region of the ERαА gene. An insertion was detected in the ERβ gene promoter next to the 715 nucleotide position. It was present in 83 % of breast cancer patients, in 67 % of them at homozygous state. Due to high frequency of the 715 insertion in the studied population we regard it as a potential marker for breast cancer.