Breast cancer is a multifactorial disease and its occurrence depends on the synergistic action of clinical, biological and environment factors and mechanisms [24–25]. In addition to these risk factors, the role of specific genes in the pathology of breast cancer is increasingly evident. The P53 gene encodes a transcription factor that binds to DNA and promotes the expression of genes that would repair cellular damage. Therefore, P53 is a tumor suppressor that sounds the alarm when DNA damage prevents the cell from turning into a cancer cell, or even inducing cell death. In the presence of a mutation, P53 gene can no longer repair the damaged DNA, which will lead to appearance of the malignant cells responsible for tumorigenesis [26–27]. In the recent decade, many studies have been conducted to assess the correlation between the polymorphism of the Arg72Pro P53 gene and the risk of breast cancer. However, these results remained very often contradictory. The meta-analysis can be an adequate tool to detect the effect of a gene in diseases with a great power of confidence. This meta-analysis evaluated the association between the variants Arg72Pro of the tumor suppressor P53 gene and breast cancer with eligibility criteria of case-control studies that had age-matched controls in HWE. All nine studies included were from the Caucasian population. Although, inclusion of other ethnic groups would be interesting, we believe that inclusion of ethnically non-biased studies improves the accuracy of our analysis.
Our results suggested a strong positive association between the Arg72Arg variant of the P53 gene and breast cancer risk. This risk was found to be 1.16-fold in the dominant genetic model and 1.13-fold in the individuals carrying the Pro allele. In addition, this work showed that, the recessive model had no protective effect against the development of breast cancer. These results were consistent in part with those of Hou et al. 2013 [28], who found in a similar study population that individuals carrying Pro allele in the dominant (OR = 1.036, 95%: 0.927–1.159), recessive (OR = 1.019, 95% CI: 0.916–1.134) and additive (OR = 1.002, 95%, 0.972–1.033) models were not protected from the disease. Goncalves et al 2013 [29] also found the same result as ours with the dominant model. However, this present meta-analysis was discordant with those of Zhuo et al.'s work that showed that the Pro allele of P53 gene was not associated with the occurrence of breast cancer [30]. The difference between our results can be explained by the presence of heterogeneity with the three genetic models, and the mixture studies with age-matched controls and unmatched controls in their analysis. Their studies also included studies whose controls were not in HWE [31–32]. The great and rigorous selection of these inclusion criteria is in fact the innovation in our present study. In addition, the meta-analyses of Goncalves et al. 2013 [29], He et al. 2011 [33] and Ma et al. 2011 [34] showed that the Arg allele of the P53 gene was not associated with the risk of breast cancer, which is consistent with our findings.
The literature is composed of contradictory conclusions regarding the association of Arg72Pro P53 gene with breast cancer risk, but most of the previous meta-analyses focused on the presence or absence of the wild-type (Arg) allele in these genetic models: dominant (Arg/Arg + Pro/Arg vs. Pro/Pro), recessive (Arg/Arg vs. Arg/Pro + Pro/Pro) and additive (Arg vs. Pro) [29, 33, 34]. However, we have found some bias in certain studies with regard to the inclusion criteria of scientific articles, which may have influenced those meta-analyses and interpretations. This bias existed in mostly studies whose distribution of Arg/Arg, Arg/Pro and Pro/Pro genotypes in controls was not in HWE [31, 32, 35–46].