p16 promoter hypermethylation is associated with increased breast cancer risk.

The current study aimed to investigate the effects of p16 hypermethylation on breast cancer quantitatively through a meta-analysis of available case-control studies (including malignant, benign and normal breast cancer tissues). The PubMed, Web of Science and EBSCO databases were searched from their inceptions to February 1, 2012. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were extracted and pooled to assess the strength of the association between p16 hypermethylation and breast cancer risk. A total of eight studies, including 691 breast cancer cases and 525 control cases, were identified for meta-analysis. Statistically significant ORs of p16 hypermethylation were obtained from the breast cancer and control groups (OR, 6.58; 95% CI, 1.15-37.75; P=0.03). However, no significant associations between the methylation and ER and PR status in breast cancer were detected (OR, 1.24; 95% CI, 0.64-2.41; P=0.52; OR, 1.49; 95% CI, 0.81-2.75; P=0.20, respectively). The meta-analysis indicated that p16 hypermethylation significantly increases breast cancer risk. However, no significant associations between the methylation and ER and PR status in breast cancer were detected.