Background: We have recently developed a new strategy for the treatment of sarcomas by using human calponin promoter to drive replication and oncolysis of herpes simplex virus (HSV-1). In order to apply this therapy to a broad spectrum of sarcoma cells, it is essential to elucidate silencing mechanisms of the calponin promoter in a subset of sarcoma cells:
Materials and methods: In this study, we investigated the mechanisms of calponin inactivation in human sarcoma tissues and cell lines through the analysis of CpG methylation of promoter region by bisulfite modification, because the 5'-flanking region of the human calponin gene was originally identified as a DNA fragment bound to the conserved methyl-CpG binding domain (MBD) of MeCP2. Furthermore, we examined the correlation between DNA methylation and expression of the calponin gene by treatment with the demethylating agent 5-Aza-CdR, and in vitro 5'CpG methylation in a luciferase reporter gene construct.
Results: Here, we have provided evidence that DNA hypermethylation of the specific 5'CpG sites in exon 1 is a mechanism accompanying decreased calponin expression in both human sarcoma tissues and cell lines.
Conclusion: These results suggest that DNA methylation may be an important mechanism regulating calponin transcription in human sarcoma cells, and thus could potentially affect the efficacies of treatment of this malignancy utilizing the human calponin promoter.