The histone protein family member X (H2AFX) is important in maintaining 
chromatin structure and genetic stability. Genetic variants in H2AFX may alter 
protein functions and thus cancer risk. In this case-control study, we genotyped 
four common single nucleotide polymorphisms (i.e., -1654A > G [rs643788], -1420G 
> A [rs8551], and -1187T > C [rs7759] in the H2AFX promoter region and 1057C > T 
[rs7350] in the 3' untranslated region (UTR)) in 467 patients with sporadic 
breast cancer and 488 cancer-free controls. All female subjects were 
non-Hispanic whites aged <or=55 years. We found that significantly increased 
risk of breast cancer was associated with variant genotypes in the H2AFX 
promoter: adjusted odds ratio [OR] = 1.80, 95% confidence interval [CI] = 
1.38-2.34 for -1654AG/GG; OR = 1.40, 95% CI = 1.07-1.83 for -1420GA/AA; and OR = 
1.65, 95% CI = 1.26-2.16 for -1187TC/CC. Furthermore, the number of variant 
alleles in the promoter haplotypes was associated with increased risks of breast 
cancer in a dose-response manner (OR = 6.08, 95% CI = 3.25-11.38; OR = 6.83, 95% 
CI = 3.83-12.18; and OR = 23.61, 95% CI = 3.95-140.99 for one, two, and three 
variant alleles, respectively) (P (trend) \ < 0.0001). Age at onset of breast 
cancer significantly decreased as the number of variant alleles increased (P 
(trend) = 0.024). However, these effects were not observed in the 3'UTR 1057C > 
T polymorphism. Therefore, we believe that H2AFX promoter polymorphisms may 
contribute to the etiology of sporadic breast cancer in young non-Hispanic white 
women. Larger association studies and related functional studies are warranted 
to confirm these findings.