| Breast cancer is the most common cancer among women in the world. Both genetic and environmental factors were involved in the cause of breast cancer. There are a lot of researches about the circadian rhythm variation and cancer susceptibility. The mutation of the circadian gene which regulates the circadian rhythm can induce the carcinogenesis development. Some basic researches showed that the PER gene, a very important member of the circadian gene family, take a very important part in the cancer development, such as chronic myeloid leukemia, prostate cancer and breast cancer. But, the study about the association between the polymorphism of PER gene and breast cancer is very few. Therefore, to get a new index of the breast cancer cause and screening the high risk people from the whole population, we hypothesized there was an association between the polymorphism of the PER3 gene and the susceptibility of the breast cancer in Chinese population.Based on hospital-community, a case-control study was conducted. All the cases have been diagnosised by pathology; the controls were matched with the cases in age frequency. All the subjects took the questionnaire and donated blood. The case and control groups were compared in terms of selected related factors to breast cancer. Differences were evaluated using theχ2 test. The associations between genotypes of the selected polymorphisms and breast cancer risk were estimated by computing the odds ratios (ORs) and 95% confidence intervals (95% CIs) from both univariate and multivariate unconditional logistic regression analysis.In our study there were 836 cases of breast cancer and 946 controls, while the average age is 51.23 years old for cases,50.99 years old for controls. Logistic regression analysis of the environment factors have found that women with a marry age more than 25 years old, a higher education level and abortion can significantly enhance the breast cancer risk(OR=3.365,4.542,2.292). Late menarche (>15 years) and more birth could decrease the risk of breast cancer(OR=0.556,0.130). In our study we have not found any associations between menses period, menses last time, age of first pregnancy, number of pregnant more than 5 month, breast feeding time and breast cancer. We also suggested that the breast benign disease, family cancer history, smoking, rich fatty intake could significantly enhance the breast cancer risk (OR=5.242,3.425,6.337 and 2.140), while vegetable intake could significantly decrease the risk of breast cancer (OR=0.423). In addition, neither alcohol intake nor exercise has been found to affect breast cancer risk in our study. We also analyzed the relationships between the length polymorphism of PER3 gene on exon 18 and the risk of breast cancer. The results showed that the frequency of the homozygous PER3-/- were 72.73% for the controls and 72.61% for the cases, the frequency of the heterozygous of PER3+/- were 25.69% for the controls and 25.60% for the cases, the frequency of the homozygous PER3+/+ were 1.59% for the controls and 1.79% for the cases. There was no association between the polymorphism of the PER3 gene and breast cancer risk in our study. But we found that the variant PER3 genotype (homozygous 5-repeat alleles) can enhance the risk of breast cancer, compared with the PER3 genotype (homozygous+heterozygous 4-repeat alleles) (OR=3.503,95%CI:1.069-11.480, OR=3.337,95%CI: 1.025～10.864) adjusted by marry age, education level, menarche age, birth, abortion, breast benign disease, family cancer history, smoking et al. However, this association was not significant after stratified by marry age, education, number of birth, abortion, breast benign disease and family history of cancer.The associations between environmental factors and the breast cancer showed in this study were accordant with previous studies. In our study the results showed that the PER3 genotype (homozygous 5-repeat alleles) could significantly enhance breast cancer risk. |
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