Open Access Technical advance

Development of a novel cell-based assay system EPISSAY for screening epigenetic drugs and liposome formulated decitabine

Sue Ping Lim1*, Raman Kumar12, Yamini Akkamsetty3, Wen Wang3, Kristen Ho1, Paul M Neilsen1, Diego J Walther4, Rachel J Suetani1, Clive Prestidge3 and David F Callen1

Author Affiliations

1 Cancer Therapeutics Laboratory, Centre for Personalized Cancer Medicine, The University of Adelaide, Adelaide, South Australia, Australia

2 Women’s & Children’s Health Research Institute Inc, North Adelaide, South Australia, Australia

3 Ian Wark Research Institute, University of South Australia, Mawson Lakes Boulevard, Mawson Lakes, South Australia, Australia

4 Max Planck Institute for Molecular Genetics, Berlin, Germany

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BMC Cancer 2013, 13:113  doi:10.1186/1471-2407-13-113

Published: 13 March 2013



Despite the potential of improving the delivery of epigenetic drugs, the subsequent assessment of changes in their epigenetic activity is largely dependent on the availability of a suitable and rapid screening bioassay. Here, we describe a cell-based assay system for screening gene reactivation.


A cell-based assay system (EPISSAY) was designed based on a silenced triple-mutated bacterial nitroreductase TMnfsB fused with Red-Fluorescent Protein (RFP) expressed in the non-malignant human breast cell line MCF10A. EPISSAY was validated using the target gene TXNIP, which has previously been shown to respond to epigenetic drugs. The potency of a epigenetic drug model, decitabine, formulated with PEGylated liposomes was also validated using this assay system.


Following treatment with DNA methyltransferase (DNMT) and histone deacetylase (HDAC) inhibitors such as decitabine and vorinostat, increases in RFP expression were observed, indicating expression of RFP-TMnfsB. The EPISSAY system was then used to test the potency of decitabine, before and after PEGylated liposomal encapsulation. We observed a 50% higher potency of decitabine when encapsulated in PEGylated liposomes, which is likely to be due to its protection from rapid degradation.


The EPISSAY bioassay system provides a novel and rapid system to compare the efficiencies of existing and newly formulated drugs that reactivate gene expression.

Cell-based assay system; Decitabine; Liposomes; Nanotechnology; CB1954; Nitroreductase