Abstract. The aim of the present study was to investigate the association between cyclin-dependent kinase inhibitor 2A (CDKN2A) and cyclin-dependent kinase inhibitor 2B (CDKN2B) methylation, and coronary heart disease (CHD), and to explore the interaction between methylation status and CHD clinical characteristics in Han Chinese patients. A total of 189 CHD (96 males, 93 females) and 190 well-matched non-CHD controls (96 males, 94 females) were recruited for the study. Methylation-specific polymerase chain reaction technology was used to examine gene promoter methylation status. Comparisons of methylation frequencies between CHD and non-CHD patients were carried out using the Chi-square test. Methylation levels of CDKN2A and CDKN2B genes were not found to be associated with the risk of CHD. However, the mean age of CDKN2A-hypermethylated participants was significantly lower than CDKN2A-unmethylated participants (58.73±5.88 vs. 62.62±5.36 years, adjusted P<0.001). Conversely, the mean age of CDKN2B-hypermethylated participants was significantly higher compared with CDKN2B-unmethylated participants (62.26±5.48 vs. 58.33±7.47 years, adjusted P=0.048). In addition, CDKN2B methylation frequencies were significantly increased in female participants compared with males (99.47 vs. 11.98%, P=0.032). In conclusion, the results indicated that CDKN2A and CDKN2B promoter methylation frequencies were significantly associated with age, and there was a gender dimorphism in CDKN2B methylation.
IntroductionCoronary heart disease (CHD) is a complex chronic disease that is caused by an imbalance between blood supply and demand in myocardium. Various environmental and genetic factors are known to contribute to onset and development of CHD (1). As of 2010, CHD was the leading cause of mortality globally, resulting in over 7 million cases of mortality (2). Therefore, association studies for CHD biomarkers have been performed worldwide (3-5) for future forefront diagnostics for the early assessment of cardiac risks.The genetic locus at chromosome 9p21 has been demonstrated to be strongly associated with the risk of CHD (6,7). Cyclin-dependent kinase inhibitor 2A (CDKN2A) and cyclin-dependent kinase inhibitor 2B (CDKN2B) genes both encode putative regulators of cyclin-dependent kinases on chromosome 9p21. Genome-wide association studies have identified that some CDKN2A or CDKN2B genetic variants are susceptible to CHD (8-10). As recently reported, many human diseases, including cardiovascular disease, could be influenced by aberrant DNA methylation modification (11). Aberrant methylation of cytosine-phosphate-guanine (CpG) islands in gene promoters is associated with transcription silencing and activity (3). However, the exact role of CDKN2A and CDKN2B methylation in cardiovascular system has not yet been fully elucidated.CDKN2A gene is involved in the regulation of cell proliferation, cell aging and apoptosis (12). However, a bidirectional role of CDKN2A gene expression has been reported in previous studies. Knösel et al (13) reported...