Abstract
DNA methylation plays an important role in tumorigenesis and development. The potential of aberrant DNA methylation to act as a biomarker for tumor diagnosis and prognostic evaluation is currently being explored. Lactate dehydrogenase C4 (LDH-C4) is a member of the cancer/testis antigen family that is expressed in a broad range of human tumor types, with particularly high expression patterns observed in lung cancer, melanoma and breast cancer. However, whether the methylation of the promoter region of LDH-C4 can be used as a tumor marker and its association with prognosis remain poorly understood. The present study aimed to determine the potential of the methylation status of LDH-C4 and DNA methyltransferase (DNMT) expression to be biological markers for the prognostic evaluation of breast cancer. Methylation-specific PCR was conducted to evaluate alterations in the methylation levels of LDH-C4. Immunohistochemical analysis was performed to assess the expression levels of DNMTs in breast cancer tissues. The association between the methylation status of LDH-C4 or the expression of DNMTs, and clinical pathological parameters was also evaluated. The results of the present study revealed that the demethylation rate of LDH-C4 in breast cancer tissues was significantly increased compared with that of adjacent tissues, and associations were identified between the demethylation of LDH-C4 and the histological grade, estrogen receptor, progesterone receptor and HER-2 status, and lymph node metastasis. The level of LDH-C4 demethylation was negatively correlated with the expression of DNMTs. Demethylation of the LDH-C4 promoter and DNMT expression predicted an unfavorable prognosis of patients with breast cancer. In addition, demethylation of the LDH-C4 promoter, high expression of DNMT3a and DNMT3b, histological grade and lymph node metastasis were all discovered to be independent prognostic factors in patients with breast cancer. In conclusion, results of the present study indicated that the demethylation of LDH-C4 and DNMT expression levels may be closely associated with the occurrence and development of breast cancer, in addition to lymph node metastasis. Thus, both may be used to assist the clinical evaluation of prognosis.