Decitabine induced demethylation of 5’ CpG-island in GADD45A leads to apoptosis in osteosarcoma cells

Khaldoun Al-Romaih, Bekim Sadikovic, Maisa Yoshimoto, Yuzhuo Wang, Maria Zielenska and Jeremy A. Squire

Year 2008, Volume 10, Issue 5

Abstract

GADD45 genes are epigenetically inactivated in various types of cancer and tumour cell lines. To date, defects of the GADD45 gene family have not been implicated in osteosarcoma (OS) oncogenesis, and the role of this pathway in regulating apoptosis in this tumour is unknown. The therapeutic potential of Gadd45 in OS emerged when our previous studies showed that GADD45A was re-expressed by treatment with the demethylation drug decitabine. In this study we analyze the OS cell lines MG63 and U2OS and show that upon treatment with decitabine a significant loss of DNA methylation of GADD45A was associated with elevated expression and induction of apoptosis. In vivo affects of decitabine treatment in mice showed that untreated control xenografts exhibited low nuclear staining for Gadd45a protein, whilst the nuclei from xenografts in decitabine treated mice exhibited increased amounts of protein and elevated apoptosis. To show the specificity of this gene for decitabine-induced apoptosis in OS, GADD45A mRNAs were disrupted using siRNA and the ability of the drug to induce apoptosis was reduced. Understanding the role of demethylation of GADD45A in re-expression of this pathway and restoration of apoptotic control is important for understanding OS oncogenesis and for more targeted therapeutic approaches.

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