Exon1 and -116 C/G Promoter Polymorphism on the X-Box DNA Binding Protein- 1 Gene is not Associated with Breast Cancer among Jordanian Women

Background: Human X -box binding protein 1 (XBP1), a critical gene in the endoplasmic reticulum stress response, is located on chromosome 22q12, which has been linked with the pathogenesis of many diseases, particularly cancers such as breast cancer (BC). Single nucleotide polymorphisms (SNPs) in the XBP1 gene can alter structure and function of the gene. In this study, polymorphism in the promoter region and exon1 of the gene XBP1 and its association with BC in Jordanian women was investigated. Methods: Polymorphism in the promoter and exon1 of XBP1 was analyzed in 100 subjects (controls: n=40; BC patients=60). −116 C/G SNP was genotyped by Polymerase Chain Reaction (PCR)-sequence specific primer technique. The odd ratios (ORs) at 95% confidence intervals (CIs) were computed to assess the strength of this association. Results: The three genotypes of the SNP (GG, GC, CC) and their allelic frequencies have nonsignificant differences between patients and control group. It was noticed that the frequencies of the mutant allele (G) were (75.8% versus 24.2%)) in the patients and control groups, respectively, while those of the normal allele (C) were (67.5% versus 32.5%). XBP1 (-116 G→C) G allele did not show significant association with BC risk (confidence interval = 0.3534- 1.2395, odds ratio = 0.6619, P= 0.197). Moreover, there were no significant mutations in the XBP1 exon1 neither in BC subjects nor control subjects. Conclusions: This is the first study to evaluate the effect of polymorphism in the promoter and exon1 of XBP1 gene in the pathogenesis of BC in Jordanian women. The results do not support a role for polymorphism in development of BC and further studies with a larger sample size and detailed data should be performed in other populations.