A novel Bifidobacterium infantis-mediated TK/GCV suicide gene therapy system exhibits antitumor activity in a rat model of bladder cancer

Abstract

Bladder cancer is the ninth most common malignancy in the world. Successful clinical management remains a challenge. In order To search for novel targeted and efficacious treatment, we sought to investigate anti-tumor activity of BI-TK suicide gene therapy system in a rat model of bladder tumors. We first constructed and tested an anaerobic Bifidobacterium infantis-mediated thymidine kinase (BI-TK) suicide gene therapy system. To test the in vivo efficacy of this system, we established a rat model of bladder tumors, which was induced by N-methyl-nitrosourea perfusion. Bifidobacterium infantis containing the HSV-TK (i.e., BI-TK) were constructed by transformation of recombinant plasmid pGEX - TK. The engineered BI-TK was injected into tumor-bearing rats via tail vein, followed by intraperitoneal injection of ganciclovir (GCV). Using the rat model of bladder tumors, we found that bladder tumor burdens were significantly lower in the rats treated with BI-TK/GCV group than that treated with normal saline control group (p <0.05). While various degrees of apoptosis of the tumor cells were detected in all groups using in situ TUNEL assay, apoptosis was mostly notable in the BI-TK/GCV treatment group. Immunohistochemical staining further demonstrated that the BI-TK/GCV treatment group had the highest level of caspase3 protein expression than that of the empty plasmid group and normal saline group (p < 0.05). Thus, our results demonstrate that the Bifidobacterium infantis-mediated TK/GCV suicide gene therapy system can effectively inhibit rat bladder tumor growth, possibly through increasing caspase 3 expression and inducing apoptosis.

Bacterial vectors for imaging and cancer gene therapy: a review

“…26 Numerous publications provide convincing evidence that genera of bacteria including Bifidobacterium and commensal Escherichia coli have potential in cancer therapy. 9,10,12,16,[27][28][29][30] This vector class compares favorably with other vectors in terms of key attributes such as safety, ease of manipulation, and production. While nonpathogenic bacteria have yet to enter clinical trial in the context of tumor targeting vectors, existing knowledge strongly indicates their suitability as a vector system for clinical use.…”

Potential antitumor therapeutic strategies of human amniotic membrane and amniotic fluid-derived stem cells

“…41,42,57,67,68 These suicide genes effectively converts non-toxic prodrugs into their highly cytotoxic forms: 65,69,70 CD converts 5-fluorocytosine into 5-fluorouracil, carboxylesterase, CPT-11, SN-38 and herpes simplex virus thymidine-kinase, ganciclovir (GCV), active form of GCV. 62,64,67,69,71,72 For example, Gu et al 73 evaluated the efficacy of the herpes simplex virus thymidine-kinase/GCV system using MSCs (MSCtk cells) in leptomeningeal glioma dissemination models. The results from this study showed that MSCtk cells exerted a strong 'bystander effect' both in vitro and in vivo conditions in the presence of GCV.…”

Salmonella-Mediated Cancer Therapy: Roles and Potential

“…In a different report, Fujimori et al created a plasmid encoding the CD gene and used it to transform Bifidobacterium longum in a system termed Bifidobacterial Selective Targeting-Cytosine Deaminase therapy. In another enzyme-prodrug strategy, the Herpes Simplex VirusThymidine Kinase (HSV-TK) gene was transformed into Bifidobacterium infantis to create the Herpes Simplex Virus-Thymidine Kinase/Ganciclovir (HSV-TK/GCV) system [13]. Thymidine kinase expressed in bacteria that specifically colonize tumor tissues can convert the non-toxic precursor ganciclovir into ganciclovir-3-phosphate, a toxic substance that kills tumor cells.…”

“…Although some of these organisms are used as monotherapy [6,8,24], most of them are used as vehicles to deliver therapeutic agents such as DNA [19], siRNA [9,28], toxins [7, 10-12, 20, 30], and prodrug-enzymes [13], or combined with other therapies [14,15,21,32] to enhance their therapeutic effect.…”