Evaluation of expression level and methylation profile of CXX1 gene in breast cancer tissue blocks.

Abstract

The hypermethylation of CpG islands in the promoter of tumor-suppressor genes (TSGs) leads to silencing the transcription of tumor suppressors, which lead to the development of cancer. The hypermethylation of CXX1 and CDH1 genes, as TSGs, plays an essential role in the development of various types of cancer, i.e., colorectal and gastric cancer. This study aims at evaluating the expression level of CXX1 and CDH1 genes and the methylation status of CXX1 CpG island's promoter in breast cancer (BC). In this study, the expression level of the CXX1 and CDH1 genes and the promoter methylation status of the CXX1 gene were evaluated in 30 paraffin-embedded tissue blocks of malignant BC and 18 benign breast lesions, using quantitative reverse transcription-PCR and methylation-specific (MS)-PCR assays, respectively. The CXX1 gene was downregulated in the malignant tissues due to the hypermethylation of the CpG islands in the promoter, compared to the control group (P = 0.031). The downregulation of CDH1 gene expression was observed in the patient group compared to control, but this reduction was not statistically significant. The results show that the risk of BC is increased with aging (P < 0.001). Furthermore, the benign breast lesions (controls) had more mobility in comparison with the malignant breast tumors (P < 0.001). In the malignant samples, the size of the mass was larger than control's mass samples (P = 0.006). In the pathophysiological state of BC, the aberrant DNA hypermethylation in CpG island of CXX1 promoter is responsible for the reduction of its expression level in BC patients.