205 SELECTIVE ANTITUMOR THERAPEUTIC EFFECT OF 5-FLUOROCYTOSINE AND INTERFERON-BETA AGAINST BREAST AND ENDOMETRIAL CANCER CELLS BY ENGINEERED STEM CELLS EXPRESSING CYTOSINE DEAMINASE AND HUMAN INTERFERON-BETA

Abstract

When genetically engineered with chemo- or immunotherapeutic genes, stem cells can exhibit a potent therapeutic efficacy combined with their strong tumour tropism. The stem cells were genetically engineered to express a bacterial cytosine deaminase (CD) gene and/or a human interferon-β (IFN-b) gene; thus, 2 stem cell lines, HB1.F3.CD and HB1.F3.CD.IFN-b, were generated, respectively. The CD gene, one of suicide gene, can convert the nontoxic prodrug 5-fluorocytosine (5-FC) to an active form, 5-fluorouracil (5-FU), which has a powerful cytotoxic effect on cancer cells. In addition, human IFN-b is a typical cytokine having an antitumour effect. Using reverse transcription-PCR (RT-PCR), we confirmed CD and/or IFN-b gene expression in HB1.F3 (maternal stem cells) and HB1.F3.CD and HB1.F3.CD.IFN-b cells and the expression of chemoattractant ligands and receptors including stem cell factor (SCF), CXCR4, c-kit, vascular endothelial growth factor (VEGF) and VEGF receptor 2 (VEGFR2) in breast (MCF-7) and endometrial cancer (Ishikawa) cells. To determine the migratory capability of engineered stem cells, we performed a modified trans-well assay. In addition, to identify their therapeutic efficacy, we co-cultured HB1.F3.CD or HB1.F3.CD.IFN-b with breast and endometrial cancer cells and cell viability was measured by MTT assay. The engineered stem cells expressed CD and IFN-b genes and several chemoattractant molecules, SCF, CXCR4, VEGF/VEGFR2 and c-kit, were strongly expressed in breast and endometrial cancer cells. These stem cells were effectively migrated to breast and endometrial cancer cells due to chemoattractant molecules secreted by breast and endometrial cancer cells. In therapeutic efficacy, the viability of breast and endometrial cancer cells treated with 5-FC was reduced in the presence of the HB1.F3.CD and HB1.F3.CD.IFN-b cells. Cell viability was more reduced when co-cultured with HB1.F3.CD.IFN-b compared with HB1.F3.CD cells. In conclusion, the results from the present study suggest that genetically modified stem cells expressing CD and IFN-b can be used as a gene-based therapy for treating breast and endometrial cancer via their tumour tropism. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (No. 2011-0005723).