DNA methylation of the hTERT gene in breast cancer revisited: Diagnostic and clinical implications

Abstract

Background: It is documented that in tumor cell lines, the hTERT gene exhibits prominent methylation at a CpG island rich region about -600 bp upstream of the transcription start site, but mixed or allelically absent around ±150 bp region. Given the potential clinical implications of the findings in breast cancer diagnostics, we set out to investigate if such findings are reproducible on primary surgically resected invasive breast carcinomas. Methods: The cohort consisted of 50 cases of freshly sampled and formalin-fixed paraffin embedded (FFPE) invasive breast cancers and normal tissue. A modified quasi-quantitative methylation specific polymerase chain reaction was used to determine methylation status in cancer relative to normal tissue at the 2 CpG island-rich regions. Results: A global hypermethylation is evident at the -600 bp region in both fresh and parallel FFPE breast cancers as compared to normal tissue. In contrast, most of the tumor and normal tissue remains unmethylated around the6150 bp region. Conclusions: Our results support further development of hTERT hypermethylation in the -600 bp region as a biomarker for breast cancer diagnostics. The unmethylated status of ±150 bp region in normal breast tissue does not support the suggestion that unmethylation is required for hTERT gene expression.