Hypoxia-targeted triple suicide gene therapy radiosensitizes human colorectal cancer cells

Abstract

The hypoxic microenvironment, an important feature of human solid tumors but absent in normal tissue, may provide an opportunity for cancer-specific gene therapy. The purpose of the present study was to investigate whether hypoxia-driven triple suicide gene TK/CD/UPRT expression enhances cytotoxicity to ganciclovir (GCV) and 5-fluorocytosine (5-FC), and sensitizes human colorectal cancer to radiation in vitro and in vivo. Stable transfectant of human colorectal HCT8 cells was established which expressed hypoxia-inducible vectors (HRE-TK/eGFP and HRE-CD/UPRT/mDsRed). Hypoxia-induced expression/function of TK, CD and UPRT was verified by western blot analysis, flow cytometry, fluorescent microscopy and cytotoxicity assay of GCV and 5-FC. Significant radiosensitization effects were detected after 5-FC and GCV treatments under hypoxic conditions. In the tumor xenografts, the distribution of TK/eGFP and CD/UPRT/mDsRed expression visualized with fluorescence microscopy was co-localized with the hypoxia marker pimonidazole positive staining cells. Furthermore, administration of 5-FC and GCV in mice in combination with local irradiation resulted in tumor regression, as compared with prodrug or radiation treatments alone. Our data suggest that the hypoxia-inducible TK/GCV+CDUPRT/5-FC triple suicide gene therapy may have the ability to specifically target hypoxic cancer cells and significantly improve the tumor control in combination with radiotherapy.

Hypoxic tumor microenvironment: Opportunities to develop targeted therapies

“…The prodrug, RSU1069, showed greater than a 30 fold increase in the normoxic to hypoxic cytotoxicity ratio compared to negative controls in vitro and also preferential cytotoxicity to hypoxic cells in vivo (Patterson, Williams, 2002). In another study, hypoxia-driven triple suicide genes TK/CD/UPRT were expressed to increase the cytotoxicity of ganciclovir (GCV) and 5-fluorocytosine (5-FC) as well as increase sensitivity of human colorectal cancer towards radiation both in vitro and in vivo (Hsiao et al, 2014). Alternative gene therapy strategies employ antisense or small interfering RNA (siRNA) delivery to hypoxic tumors for inducing tumor apoptosis (Mizuno et al, 2005, Sun et al, 2010).…”

Therapeutic effects of adenovirus‑mediated CD and NIS expression combined with Na131I/5‑FC on human thyroid cancer

“…A previous study indicated that NIS expression is primarily controlled by the thyroid-selective transcription factors paired box gene 8 (Pax-8) and NK2 homeobox 1 (Nkx2.1) in thyroid cancer (31). Pax-8 and Nkx2.1 target the NIS upstream enhancer through the cardiac homeobox transcription factor Nkx2 (16,32).…”

“…Previous advances propose additional improvements to CDA suicide gene therapy (32). The uracil phosphoribosyl transferase (UPRT) gene from Escherichia coli encodes uracil phosphoribosyltransferase, which converts uracil and 5-phosphoribosyl-1-R-diphosphate to uridine monophosphate (UMP).…”

Improved sensitization effect of sunitinib in cancer cells of the esophagus under hypoxic microenviroment

“…Radiotherapy has been used either as a definitive therapy for esophageal cancer patients with locally advanced disease or as an adjuvant therapy following radical esophagectomy for esophageal cancer patients (1)(2)(3). However, an hypoxic microenvironment exists in esophageal carcinomas, which leads to radiation resistance and poor clinical outcomes, and may be an important determinant of radioresistance (4,5). Free oxygen radicals are generated during radiotherapy that induce DNA damage and kill tumor cells.…”

“…Free oxygen radicals are generated during radiotherapy that induce DNA damage and kill tumor cells. The lack of oxygen directly activates the expression of hypoxia-inducible factor 1 (HIF-1), which consists of an oxygen-sensitive subunit, HIF-1α, and a constitutively expressed subunit, HIF-1β (5,6). HIF-1 is a pivotal regulatory factor that enables tumor cells to endure an hypoxic microenvironment, and promotes tumor growth, angiogenesis, invasion and metastasis (6).…”