A novel fusion suicide gene yeast CDglyTK plays a role in radio-gene therapy of nasopharyngeal carcinoma

Abstract

To investigate a novel suicide gene for nasopharyngeal carcinoma (NPC) therapy, the yCDglyTK gene was constructed by fusing yeast cytosine deaminase (CD) and herpes simplex type 1 thymidine kinase. The expression of the yCDglyTK gene was detected by RT-PCR and Western blotting, and its bioactivity was demonstrated by an MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay. An animal study was carried out in which BALB/C nude mice bearing yCDglyTK gene-modified tumors were treated with prodrugs and radiation. Our results revealed that the yCDglyTK gene could be expressed in CNE-2 cells in vitro. In MTT analysis, at the transfection rate of 10%, 66% cells were killed. The synergistic effect of CD and TK showed 91% of yCDglyTK-transfected cells were killed with the treatment of 5-fluorocytosine (5-FC) alone, 60% killed with ganciclovir (GCV) alone, and 75% killed with 5-FC and GCV together. In vivo, the tumor volume in all of the four prodrugs and/or radiation-treated groups were significantly different from that in the PBS-controlled group (Po.01); also yCDglyTK þ prodrug þ radiation group was different from the other three groups (Po.05). Our findings suggested there was a synergistic antitumor effect when combining suicide gene therapy and radiation, and yCDglyTK has potent antitumor efficacy and may be a candidate suicide gene for cancer therapy.

Baculovirus-transduced bone marrow mesenchymal stem cells for systemic cancer therapy

“…Some studies have in fact shown the CD/5-FC system to be more potent than HSVtk/GCV system in in vitro eradication of human colorectal carcinoma, hepatocellular carcinoma and even Epstein-Barr viruspositive B lymphocytes; [35][36][37] others have combined the two systems and reported an enhanced antitumor activity in vitro and in vivo. [38][39][40] All these previous studies in the field seem to indicate the success of gene-directed enzyme prodrug therapy systems in eradicating a large range of tumor types, highlighting thus, the broad usage of these gene-directed enzyme prodrug therapy systems. It will be interesting to investigate whether baculovirus-mediated genetic modification of MSCs is able to produce a good therapeutic effect on cancer treatment when coupled with the CD/5-fluorouracil system or with both the CD/5-fluorouracil and the HSVtk/GCV systems.…”

Suicide gene delivery by calcium phosphate nanoparticles: A novel method of targeted therapy for gastric cancer

“…The resulting metabolites are integrated into the DNA and RNA of cells, leading to strand termination and eventual cell death. 6 While bCD is capable of acting as a suicide gene, it has been reported that yeast CD (yCD) is much more powerful in this regard. 7,8 Recently, a novel fusion suicide gene was developed consisting of both yCD and HSV-1 TK, termed yCDglyTK; when expressed in tumor cells, it performed prodrug conversion while rendering the cells more sensitive to radiation therapy.…”

“…7,8 Recently, a novel fusion suicide gene was developed consisting of both yCD and HSV-1 TK, termed yCDglyTK; when expressed in tumor cells, it performed prodrug conversion while rendering the cells more sensitive to radiation therapy. 6 Gene therapy is, of course, most effective when delivery is both efficient and safe, especially when dealing with cancer. However, it has often proven difficult to find a balance between efficiency and safety.…”

Targeted gene therapy in radiotherapy

“…20 This so called double suicide gene therapy approach has been evaluated in combination with radiotherapy in preclinical and also phase I clinical studies. [20][21][22][23] Yeast CD/HSV-tk fusion gene was tested in combination with radiation and pro-drugs in CNE-2 nasopharyngeal carcinoma xenografts model, demonstrating a synergistic anti-tumor effect. 21 In another study, using the bacterial CDglyTK fusion gene, the addition of pro-drugs 5-FC and gancyclovir increased the radiosensitivity of prostate cancer and glioma cells in vitro and showed a significant anti-tumor effect in a preclinical model of prostate cancer.…”

“…[20][21][22][23] Yeast CD/HSV-tk fusion gene was tested in combination with radiation and pro-drugs in CNE-2 nasopharyngeal carcinoma xenografts model, demonstrating a synergistic anti-tumor effect. 21 In another study, using the bacterial CDglyTK fusion gene, the addition of pro-drugs 5-FC and gancyclovir increased the radiosensitivity of prostate cancer and glioma cells in vitro and showed a significant anti-tumor effect in a preclinical model of prostate cancer. 22 Results from phase I clinical trial in patients with locally recurrent prostate cancer, indicated that this double suicide therapy is a relatively safe and effective method for increasing the therapeutic index of radiation.…”