Abstract
The Ferritin heavy polypeptide-like 17 (Fthl17) gene is a member of the cancer/testis antigen gene family, and is preferentially expressed in cancer cells and in testis. Although DNA methylation has been linked to the regulation of human FTHL17 gene expression, detailed epigenetic regulation of its expression has not been investigated. To address this, we assessed the epigenetic regulation of murine Fthl17 gene expression in cancer cells and germ cells. Fthl17 was more highly expressed in testis, a murine lung cancer cell line, KLN205, and in germline stem cells (GSCs) than in normal lung tissues. Furthermore, the Fthl17 expression level in GSCs was significantly higher than in KLN205 cells. We performed bisulfite-sequencing and luciferase (luc) reporter assays to examine the role of DNA methylation of the Fthl17 promoter in the regulation of Fthl17 expression. In KLN205 cells, testis, and GSCs, the Fthl17 5’-upstream region was hypo-methylated compared with normal lung tissues. Luc reporter assays indicated that hypo-methylation of the -0.6 kb to 0 kb region upstream from the transcription start site (TSS) was involved in the up-regulation of Fthl17 expression in KLN205 cells and GSCs. Because the -0.6 kb to -0.3 kb or the -0.3 kb to 0 kb region were relatively more hypo-methylated in KLN205 cells and in GSCs, respectively, compared with other regions between -0.6 kb to 0 kb, those regions may contribute to Fthl17 up-regulation in each cell type. Following treatment with 5-Azacytidine, the -0.3 kb to 0 kb region became hypo-methylated, and Fthl17 expression was up-regulated in KLN205 cells to a level comparable to that in GSCs. Together, the results suggest that hypo-methylation of different but adjacent regions immediately upstream of the Fthl17 gene contribute to differential expression levels in lung cancer cells and GSCs, and hypo-methylation of the TSS-proximal region may be critical for high level expression.
Highlights
Cancer/testis antigen (CTA) genes were identified as human tumor-specific antigen genes which are expressed in normal testis and various cancers, though their functions in germ cells and tumors are still unclear
The results suggest that hypo-methylation of -1.4 kb to -0.3 kb contributes to the regulation of Ferritin heavy polypeptide-like 17 (Fthl17) expression in KLN205 cells
The results suggest that hypo-methylation of -0.6 kb to 0 kb may play a role on further up-regulated expression of Fthl17 in testis
Summary
Cancer/testis antigen (CTA) genes were identified as human tumor-specific antigen genes which are expressed in normal testis and various cancers, though their functions in germ cells and tumors are still unclear. The expression of MAGE-A1, and other MAGE-A family genes, correlated with the DNA methylation levels of their respective promoter regions in human tumor tissues and in cancer cell lines [3,4]. Many CTA gene homologs are transcribed from hypo-methylated regions in primordial germ cells [5], implicating DNA demethylation in the regulation of their expression. Taken together, these data suggest that DNA methylation plays a fundamentally important role in regulating the expression of CTA genes
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have