TOX3 and FOXA1 proteins are believed to be involved in the susceptibility of breast cancer. rs4784227-CASC16 and rs4782447-ACSF3, as single nucleotide polymorphisms (SNPs), located at the 16q may affect the FOXA1 DNA binding sequence change and therefore may enhance the FOXA1-binding affinity to the promoter of TOX3 gene. This study aimed to investigate the association of these SNPs/haplotypes with breast cancer susceptibility in an Iranian population. We conducted a case-control study of 1072 blood samples (505 breast cancer patients and 567 controls). Genotyping of rs4784227-CASC16 and rs4782447-ACSF3 SNPs was carried out by ARMS-PCR. Moreover, statistical analysis was done using SPSS version 20.0 (IBM Inc., Chicago, IL, USA), PHASE v 2.1 and SNP analyser 2.0. There was a strongly significant statistical association between alleles and genotypes of rs4784227-CASC16 with breast cancer risk in our study population (p<0.05). Moreover, a significant association was demonstrated between TA haplotype and breast cancer risk (OR=0.78; 95% CI (0.62-0.96); P- value =0.025). In this respect, although we did not observe a statistically significant association between rs4782447-ACSF3 with breast cancer susceptibility, the combination of the effects of rs4784227-CASC16 and rs4782447-ACSF3 SNPs may also affect the risk. This is in line with other studies suggesting these SNPs as risk-associated polymorphisms which may lead to a change in the affinity of FOXA1, as a distal enhancer, to TOX3 and thus change in TOX3 expression, which can eventually affect the risk of breast cancer.
Keywords: carcinoma; chromatin remodelling; enhancer element; epidemiology; genetic variation.