Abstract 2051: Hypoxia-induced triple suicide gene TK/CD/UPRT expression enhances cytotoxicity to GCV and 5-FC and radiosensitization in human colorectal cancer cells

Abstract

Abstract The hypoxic microenvironment, an important feature of human solid tumors but absent in normal tissues, may provide an opportunity for cancer-specific gene theapy. We constructed two vectors, both under the control of nine copies of hypoxia responsive element (HRE): (1) a herpes simplex virus type 1 thymidine kinase (TK) and enhanced green fluorescent protein (eGFP) fusion gene, and (2) a triple-fusion-gene, cytosine deaminase (CD), uracil phosphoribosyltransferase (UPRT) and monomeric DsRed (mDsRed). Human colorectal cancer cells (HCT8) were transfected with these plasmids, singly or in combination. Stable HCT8-HRE cells were established that contained and expressed the hypoxia-inducible vectors (i.e. HRE-TK/eGFP, HRE-CD/UPRT/mDsRed, or both HRE-TK/eGFP and HRE-CD/UPRT/mDsRed), as assessed by RT-PCR, Western blots and fluorescence microscopy analysis. In in vitro studies, we showed that hypoxia-induced TK/eGFP and CD/UPRT/mDsRed expression not only increased cytotoxicity to GCV and 5-FC, but also led to significant radiosensitization. In HCT8-HRE tumors transplanted in athymic mice, the distribution of TK/eGFP and CD/UPRT/mDsRed co-localized with that of the hypoxia marker pimonidazole. In addition, the administration of GCV and 5-FC in combination with local irradiation resulted in significant tumor regression, greater than that observed with drug or radiation treatment alone. Our data suggest that the hypoxia-inducible TK/GCV+CDUPRT/5-FC triple gene therapy has the ability to specifically target hypoxic cancer cells and significantly improve tumor control in combination with radiotherapy. This novel model is a valuable tool for studying tumor hypoxia and hypoxia-targeted radio-gene therapy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2051. doi:10.1158/1538-7445.AM2011-2051