Decreased expression of the CHD5 gene and its clinicopathological significance in breast cancer: Correlation with aberrant DNA methylation

Chromodomain helicase DNA binding protein 5 (CHD5) has been identified as a tumor suppressor in mouse models. Downregulation of CHD5 gene expression is frequently observed in breast cancer cells and tissues. This may be explained by deletions or other mutations; however, alternative mechanisms require investigation. Therefore, the present study evaluated whether CHD5 aberrant methylation has a role in primary breast tumors. A total of 389 patients with primary breast cancer (including 252 paraffin-embedded specimens and 137 fresh-frozen samples) were enrolled in the present study. In the current study, reverse transcription-polymerase chain reaction (RT-PCR) and nested-methylation-specific PCR were used to analyze the mRNA expression and promoter methylation of CHD5 genes in a large cohort of breast cancer patients, and to investigate their associations with the clinicopathological features of tumors. CHD5 expression was significantly suppressed in breast cancer tissues compared with normal breast tissues when analyzed by RT-PCR. Furthermore, DNA methylation of CHD5 was more prevalent in breast tumors than in normal tissues. CHD5 mRNA levels correlated with the degree of CHD5 methylation in breast cancer tissues. Clinicopathological correlation analysis revealed that CHD5 promoter methylation was associated with estrogen receptor and progesterone receptor status. Thus, downregulation of CHD5, mediated by abnormal methylation, may contribute to the development and progression of breast cancer.