Polymorphic variants of the PPP1R21 gene associated with the level of sex hormone-binding globulin and the risk of various stages of breast cancer

Aim. To assess the relationship of polymorphic gene variants associated with the level of sex hormone-binding globulin (SHBG) according to genome-wide association studies (GWAS) with the risk of stage I–II and stage III-IV breast cancer. Materials and methods. A comparative genetic analysis was carried out on samples of patients with breast cancer: 254 patients with stages I–II and 91 with stages III–IV, and 1140 females of the control group. The paper considers 4 single nucleotide substitutions associated with the level of circulating SHBG according to GWAS: g.107546375AG PRMT6 (rs17496332), g.27519736TC GCKR (rs780093), g.48419260TC PPP1R21 (rs10454142), g.98364050TA BAIAP2L1 (rs3779195). Results. Differences in the involvement of polymorphic variants of SHBG candidate genes in the development of stages I–II and III–IV breast cancer were revealed. The rs10454142 TC polymorphic variant in the PPP1R21 gene is associated with the risk of stage I–II breast cancer: women with an allelic variant of this locus have a higher risk of early-stage disease (T/T vs. T/C vs. C/C, odds ratio 1.35, 95% confidence interval 1.05-1.75; p=0.021; ppermutat=0.027). Also, an increase in the number of C alleles in the female genotype increased the risk of stage I–II breast cancer by 17–18% per allele. There were no associations of polymorphic variants of SHBG candidate genes with the risk of severe disease (stage III–IV). The single nucleotide substitution rs10454142 TC in the PPP1R21 gene and the single nucleotide polymorphisms strongly linked to it are functionally significant (located in the regions of enhancers and promoters) in the epithelial and myoepithelial cells of the mammary gland and liver, affect the level of genome methylation, and are associated with the level of GTF2A1L gene expression.