Single agent- and combination treatment with two targeted suicide gene therapy systems is effective in chemoresistant small cell lung cancer cells.

BACKGROUND: Transcriptional targeted suicide gene (SG) therapy driven by the insulinoma-associated 1 (INSM1) promoter makes it possible to target suicide toxin production and cytotoxicity exclusively to small cell lung cancer (SCLC) cells and tumors. It remains to be determined whether acquired chemoresistance, as observed in the majority of SCLC patients, desensitizes SCLC cells to INSM1 promoter-driven SG therapy. METHODS: A panel of SCLC cell lines resistant to clinically relevant chemotherapeutics was characterized regarding the expression of proteins involved in response to chemotherapy and regarding INSM1 promoter activity. Sensitivity towards INSM1 promoter-driven SG therapy was tested using different systems: Yeast cytosine deaminase-uracil phosphoribosyl transferase (YCD-YUPRT) in combination with the prodrug 5-fluorocytosine (5-FC) or Escherichia coli nitroreductase (NTR) together with the bromomustard prodrug SN27686. RESULTS: The chemoresistant cell lines displayed heterogeneous expression profiles of molecules involved in multidrug resistance, apoptosis and survival pathways. Despite this, the INSM1 promoter activity was found to be unchanged or increased in SCLC chemoresistant cells and xenografts compared to chemosensitive variants. INSM1 promoter-driven SG therapy with YCD-YUPRT/5-FC or NTR/SN27686, was found to induce high levels of cytotoxicity in both chemosensitive and chemoresistant SCLC cells. Moreover, the combination of INSM1 promoter-driven YCD-YUPRT/5-FC therapy and chemotherapy, as well as the combination of INSM1 promoter-driven YCD-YUPRT/5-FC and NTR/SN27686 therapy, was observed to be superior to single agent therapy in chemoresistant SCLC cells. CONCLUSIONS: Collectively, the present study demonstrates that targeted SG therapy is a potent therapeutic approach for chemoresistant SCLC patients, with the highest efficacy achieved when applied as combination SG therapy or in combination with standard chemotherapy.

A simple protocol for preparation of a liposomal vesicle with encapsulated plasmid DNA that mediate high accumulation and reporter gene activity in tumor tissue.

The systemic delivery of gene therapeutics by non-viral methods has proven difficult. Transfection systems that are performing well in vitro have been reported to have disadvantageous properties such as rapid clearance and short circulation time often resulting in poor transfection efficiency when applied in vivo. Large unilaminary vesicles (LUV) with encapsulated nucleic acids designated stabilized-plasmid-lipo-particle (SPLP) have showed promising results in terms of systemic stability and accumulation in tumor tissue due to the enhanced permeability and retention effect (EPR). We have developed a simple protocol for the research-scale preparation of SPLPs from commercially available reagents with high amounts of encapsulated plasmid DNA. The SPLPs show properties of promising accumulation in tumor tissue in comparison to other organs when intravenously injected into xenograft tumor-bearing nude mice. Although transcriptionally targeted suicide gene therapy was not achieved, the SPLPs were capable of mediating reporter gene transfection in subcutaneous flank tumors originating from human small cell lung cancer.

Targeted cytosine deaminase-uracil phosphoribosyl transferase suicide gene therapy induces small cell lung cancer-specific cytotoxicity and tumor growth delay.

PURPOSE: Small cell lung cancer (SCLC) is a highly malignant cancer for which there is no curable treatment. Novel therapies are therefore in great demand. In the present study we investigated the therapeutic effect of transcriptionally targeted suicide gene therapy for SCLC based on the yeast cytosine deaminase (YCD) gene alone or fused with the yeast uracil phosphoribosyl transferase (YUPRT) gene followed by administration of 5-fluorocytosine (5-FC) prodrug. EXPERIMENTAL DESIGN: The YCD gene or the YCD-YUPRT gene was placed under regulation of the SCLC-specific promoter insulinoma-associated 1 (INSM1). Therapeutic effect was evaluated in vitro in SCLC cell lines and in vivo in SCLC xenografted nude mice using the nonviral nanoparticle DOTAP/cholesterol for transgene delivery. RESULTS: INSM1-YCD/5-FC and INSM1-YCD-YUPRT/5-FC therapy induced high cytotoxicity in a range of SCLC cell lines. The highest therapeutic effect was obtained from the YCD-YUPRT fusion gene strategy. No cytotoxicity was induced after treatment of cell lines of other origin than SCLC. In addition the INSM1-YCD-YUPRT/5-FC therapy was superior to an established suicide gene system consisting of the herpes simplex virus thymidine kinase (HSVTK) gene and the prodrug ganciclovir. The superior effect was in part due to massive bystander cytotoxicity of YCD-YUPRT-produced toxins. Finally, INSM1-YCD-YUPRT/5-FC therapy induced significant tumor growth delay in SCLC xenografts compared with control-treated xenografts. CONCLUSIONS: The current study is the first to test cytosine deaminase-based suicide gene therapy for SCLC and the first to show an antitumor effect from the delivery of suicide gene therapeutics for SCLC in vivo.

Specifically targeted gene therapy for small-cell lung cancer.

Small-cell lung cancer (SCLC) is a highly malignant disease with poor prognosis. Hence, there is great demand for new therapies that can replace or supplement the current available treatment regimes. Gene therapy constitutes a promising strategy and relies on the principle of introducing exogenous DNA into malignant cells causing them to die. Since SCLC is a highly disseminated malignancy, the gene therapeutic agent must be administered systemically, obligating a high level of targeting of tumor tissue and the use of delivery vehicles designed for systemic circulation of the therapeutic DNA. This review describes and discusses the current status of the application of gene therapy in relation to SCLC.