Aberrant DNA methylation of integrin α4: A potential novel role for metastasis of cholangiocarcinoma

Purpose Although the altered expression of integrin α4 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 α4 gene in CC. Methods 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 methylationspecific polymerase chain reaction. Results The frequency of DNA methylation was 55.17% (16 of 29) in the CC specimens (P < 0.001). Also, transcripts of the integrin α4 gene were decreased in all CC tissues in which there was DNA methylation of the integrin α4 gene. In addition, the downregulated expression of integrin α4 in CC cells with hypermethylation of the integrin α4 gene was restored by treatment with 5-aza-2'-deoxycytidine, a DNA methyltransferase inhibitor. Moreover, we found that DNA methylation of integrin α4 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 α4. Conclusions Taken together, these results suggest that loss of the integrin α4 gene is caused by aberrant DNA methylation of the 5'-CpG island site of the gene, and methylation of the integrin α4 gene can be a useful marker of metastasis of CC.