Background: A common polymorphism of the AluYb8 insertion in the MUTYH gene (AluYb8MUTYH), which led to the increase of oxidative DNA damage and acceleration of chronic diseases, was previously detected. Considering the relationship between carcinogenesis and oxidative stress, an investigation was held on whether the common variant of the MUTYH gene increases the risk for gastric and breast cancers.
Methods: The AluYb8MUTYH allele frequencies of 545 breast cancer patients and 762 gastric cancer patients were analyzed and compared with that of the healthy control group using the Chi-square test. The binary logistic regression model was used to examine the association between the polymorphism genotypes and cancer risk. Genomic DNA specimens from the investigated population were tested by polymerase chain reaction in agarose gel electrophoresis. According to the insertion absence or presence of the variant segment, the patterns for the AluYb8MUTYH genotypes were classified as a homozygous of absence/absence (A/A) and presence/presence (P/P) or a heterozygous of absence/presence (A/P).
Results: The variant allele frequency (insertion present, P) was inclined to be enhanced in breast cancer patients as compared with the normal female controls (46.8% versus 43.3%), and also, in gastric cancer patients, as compared with the general normal controls (45.1% versus 43.9%). However, a significantly different P allele frequency was only detected between the early-onset breast cancerpatients (<55 years old) and their counterpart female controls (46.6% versus 40.9%, p=0.042; OR=1.26, 95% CI, 1.01–1.56), as well as between the early-onset gastric cancer patients and their respective controls (49.2% versus 41.3%, p=0.042; OR, 1.37; 95% CI, 1.02–1.85). Comparisons on the genotypes of AluYb8MUTYH show that this variation of MUTYH has also a significantly higher prevalence in the early-onset cancer patients, either in breast or gastric cancer patients, than that in their counterpart controls.
Conclusions: The AluYb8MUTYH allele frequency can be associated with the early-onset breast and gastric cancer in the Chinese population.Probably, there is importance in screening the carriers with the susceptibility alleles to evaluate their risk of breast and gastric cancer for further research.