Preliminary mechanism on the methylation modification of Dkk-1 and Dkk-3 in hepatocellular carcinoma

Wnt/beta-catenin signaling pathway, having a crucial role in regulating diverse cellular processes, can be a new therapeutic target in cancer. To investigate the role of Dkk-1 (Dickkopf-1) and Dkk-3 in tumors and cirrhoses of the liver tissue in hepatocellular carcinoma (HCC), tissues from 38 patients with HCC resections including 5 patients who underwent hemangioma surgery of adjacent tumor tissues at the same time were obtained. Tissues were divided into three groups (nonfibrosis, cirrhosis, and carcinoma) through hematoxylin-eosin (HE) staining. Methylation-specific polymerase chain reaction (PCR) (MSP) measured the methylation status, and reverse transcription-PCR tested the messenger RNA (mRNA) levels, and immunohistochemical analysis provided levels of protein expression. The methylation detection rate of Dkk-1 and Dkk-3 was the highest (P < 0.05) and the mRNA levels of Dkk-1 and Dkk-3 were the lowest (P < 0.05) in the carcinoma tissues. The mRNA levels of beta-catenin were significantly higher in the carcinoma tissue than the other tissues (P < 0.05). The expression of Dkk-1 and Dkk-3 was significantly higher in the carcinoma tissues than the other tissues (P < 0.05); but the beta-catenin expression was the highest (P < 0.05). Compared with the control, the mRNA levels of beta-catenin in the Dkk-1 and Dkk-3 silencing cells increased 5.34 (P < 0.05) and 3.5 times (P > 0.05). After the interference of 5-aza-2'-deoxycytidine, the mRNA levels of Dkk-1 and Dkk-3 significantly increased 58.9 and 59.3 times (P < 0.0001), and the mRNA levels of beta-catenin decreased 6.02 times (P < 0.05). In the process of HCC, the abnormal activity of Wnt/beta-catenin signaling may be associated with the methylation of Dkk-1 and Dkk-3.