Association between Promoter Hypermethylation of the p16INK4a and hTERT Genes and Their Protein Expressions in Human Breast Cancer

Abstract

INK4a and human telomerase reverse transcriptase (hTERT ) genes and the p16 and hTERT protein expressions in invasive ductal carcinoma of the breast. In addition, we evaluated the relationship between the methylation status of the two genes and their protein expressions. Methods: We performed methylation-specific PCR (MSP) and immunohistochemical staining in 63 breast cancer specimens. Results: There was no statistical association between p16 INK4a gene methylation and the histological grade (tumor grade, tumor size and lymph node status). Methylation of the hTERT promoter did show significant differences according to the histological tumor grade and tumor size, but there was no clinical significance. Methylation of the p16 INK4a and hTERT genes was found in 22.2% and 31.8% of the specimens, respectively. A negative p16 protein expression (0-10% expression rate) was observed in 38.1% of the specimens (24 of 63). A positive hTERT expression (more than a 25% expression rate) was observed in 73.0% of the specimens (46 of 63). There was no statistical significance in the relationship between the methylation status and the protein expression. Conclusion: Our data suggest that methylation of the p16 and hTERT genes is not associated with their protein expressions according to Immunohistochemisty. There seemed to be another complicated mechanism for p16 inactivation and hTERT activation in breast cancer. (J Breast Cancer 2007; 10:59-67)