JAM3 functions as a novel tumor suppressor and is inactivated by DNA methylation in colorectal cancer

PURPOSE: JAM3, an adhesion and transmigration regulatory element, is abundantly expressed in intestinal epithelial cells. However, its expression and function in colorectal cancer (CRC) remain unknown. In this study, we explored its epigenetic mechanism and biological role in CRC. PATIENTS AND METHODS: Bioinformatics analysis was used to analyze the expression and methylation level of JAM3 in CRC. Methylation and expression status of JAM3 were then validated by quantitative methylation-specific PCR (qMSP) and quantitative PCR in tissues, plasma samples, and cell lines. Flow cytometry, Western blot, transwell, siRNA, colony formation, and transfection were used to evaluate the biological function of JAM3. RESULTS: We initially found that JAM3 was frequently methylated and downregulated in CRC based on bioinformatics tools. qMSP validation showed that the methylation levels of JAM3 were increased in 75% (18/24) of CRC tissues, 61% (11/18) plasma samples, and all four CRC cell lines and were significantly associated with tumor stage in CRC tissues. Moreover, JAM3 was downregulated in primary CRC tissues, plasma samples, and CRC cell lines as compared with that in nonmalignant controls, although its expression could be recovered after demethylation treatment. Restoration of JAM3 repressed CRC cell viability, colony formation, and migration. In addition, siRNA-mediated depletion of JAM3 in NCM460 cells improved the clonogenicity and migration capability, whereas it suppressed cell apoptosis and cell-cycle arrest. These functional effects were accompanied with alterations of several epithelial cell markers, including E-cadherin, vimentin, phosphor-β-catenin (ser552), and TJP1, which were responsible for epithelial–mesenchymal transition. CONCLUSION: The findings indicated that JAM3 may be a novel tumor suppressor gene with epigenetic reduction in CRC and can be used as a potential noninvasive biomarker for CRC diagnosis.