Aberrant DNA methylation of integrin alpha 4: a potential novel role for metastasis of cholangiocarcinoma

Abstract

Although the altered expression of integrin alpha 4 is known to be associated with transformation or metastasis in several human cancers, the information on cholangiocarcinoma (CC) is still poor. In this study, we investigated the promoter methylation status of integrin alpha 4 gene in CC. A total of 29 CC, 19 adjacent non-tumor-containing tissue and 15 normal liver specimens were used for identification of gene methylation status by methylation-specific polymerase chain reaction. The frequency of DNA methylation was 55.17% (16 of 29) in the CC specimens (P < 0.001). Also, transcripts of the integrin alpha 4 gene were decreased in all CC tissues in which there was DNA methylation of the integrin alpha 4 gene. In addition, the downregulated expression of integrin alpha 4 in CC cells with hypermethylation of the integrin alpha 4 gene was restored by treatment with 5-aza-2'-deoxycytidine, a DNA methyltransferase inhibitor. Moreover, we found that DNA methylation of integrin alpha 4 was detected in all CC tissues obtained from patients with LN metastasis (7/7). Furthermore, phosphorylation of paxillin, cell migration-related molecule, was regulated by silencing of integrin alpha 4. Taken together, these results suggest that loss of the integrin alpha 4 gene is caused by aberrant DNA methylation of the 5'-CpG island site of the gene, and methylation of the integrin alpha 4 gene can be a useful marker of metastasis of CC.