ABSTRACT
BACKGROUND: We recently demonstrated a 100% increase in the survival period with ganciclovir (GCV) therapy in mice hearing orthotopic HSV-TK-positive non-small cell lung cancer (NSCLC) tumors. However, long-term survival was not achieved. The aim of the present study was to evaluate tumor growth during extended GCV therapy and to monitor the herpes simplex virus thymidine kinase (HSV-TK) gene and protein in tumors at different time points. MATERIALS AND METHODS: The human NSCLC cell line KNS 62 was retrovirally transduced with the HSV-TK30 gene. Cell suspensions in which 100% or 25% of the cells were TK30-positive were inoculated subcutaneously in SCID bg mice. Tumor growth was evaluated during GCV therapy and HSV-TK DNA, RNA and protein were analyzed at different time points using PCR, RT-PCR and immunoblotting. RESULTS: HSV-TK DNA, RNA and TK30 protein were demonstrated in the tumors 21 days after subcutaneous tumor inoculation. TK-positive tumors regressed during GCV therapy and tumors in which 25% of the cells were TK-positive grew significantly more slowly than control tumors did. After 4 weeks of GCV therapy, HSV-TK DNA, RNA and TK protein were not detectable in the remaining tumors, which were therefore resistant to further GCV therapy. CONCLUSION: Prodrug therapy of the NSCLC cell line KNS 62, including bystander effects, is sufficient. Nevertheless, GCV-resistant tumors develop after functional loss of the TK gene. In the clinical context, further studies will need to evaluate immunological bystander effects or combinations with other drugs.
Subject(s)
Carcinoma, Non-Small-Cell Lung/therapy , Ganciclovir/pharmacology , Lung Neoplasms/drug therapy , Animals , Carcinoma, Non-Small-Cell Lung/drug therapy , Carcinoma, Non-Small-Cell Lung/enzymology , Carcinoma, Non-Small-Cell Lung/genetics , Cell Division/drug effects , Cell Line, Tumor , Drug Resistance, Neoplasm , Ganciclovir/pharmacokinetics , Gene Expression , Genetic Therapy/methods , Humans , Immunoblotting , Lung Neoplasms/enzymology , Lung Neoplasms/genetics , Lung Neoplasms/therapy , Mice , Mice, SCID , Prodrugs/pharmacokinetics , Prodrugs/pharmacology , Reverse Transcriptase Polymerase Chain Reaction , Simplexvirus/enzymology , Simplexvirus/genetics , Thymidine Kinase/genetics , Thymidine Kinase/metabolism , Transduction, Genetic , Xenograft Model Antitumor AssaysABSTRACT
BACKGROUND AND AIMS: The administration of endostatin, a potent anti-angiogenic agent, will be required for extended periods of time as a cancer treatment. The aim of the present study was to induce endogenous endostatin secretion in a continuous fashion, based on retroviral gene transfer. The tumor response was evaluated in an orthotopic murine tumor model of human lung cancer. MATERIALS AND METHODS: Human non-small-cell lung cancer cells (KNS 62) were retrovirally transduced with the human endostatin gene. An orthotopic murine xenotransplant model was used to investigate tumor growth, metastases and survival. After 4 weeks of subcutaneous growth, endostatin expression was measured by immunoblot analysis in tumor lysates. RESULTS: The growth of the subcutaneous tumors was significantly delayed, and orthotopic tumor growth and pleural metastases were significantly reduced in endostatin-transduced KNS 62 tumors. Prolongation of survival subsequent to orthotopic tumor induction was demonstrated. Strong endostatin expression was found in subcutaneous tumors after 4 weeks. CONCLUSION: Retroviral transduction of the human endostatin gene is capable of achieving long-term endostatin expression. Endostatin transduction provides significant anti-tumor effects with regard to local tumor growth, metastases and survival.
Subject(s)
Antineoplastic Agents/administration & dosage , Carcinoma, Non-Small-Cell Lung/drug therapy , Endostatins/administration & dosage , Lung Neoplasms/drug therapy , Animals , Antineoplastic Agents/therapeutic use , Endostatins/therapeutic use , Female , Gene Transfer Techniques , Humans , Immunoblotting , Mice , Mice, SCID , Neoplasm Transplantation , Transplantation, Heterologous , Tumor Cells, CulturedABSTRACT
BACKGROUND: Therapy failures have been reported for retroviral gene transfer of herpes simplex virus thymidine kinase (HSV-TK) gene followed by systemic ganciclovir application in human lung cancer. Use of the HSV-TK mutant TK30 in combination with a VSV-G pseudotyped retroviral vector was found to enhance the efficacy of prodrug therapy. The present study evaluated this therapeutic strategy in human non-small cell lung cancer cell lines in a preclinical murine xenotransplant model. METHODS: Intrathoracally induced by HSV-TK30 transduced non-small cell lung cancer cell lines Colo 699 (adenocarcinoma) and KNS 62 (squamous cell carcinoma) were monitored for local tumor growth, survival, and metastases. So-called bystander effects were investigated in tumors consisting of as little as 25% TK30 transfected cells and by analysis of gap junctional protein connexin-43 expression. RESULTS: Survival was significantly prolonged, and tumor growth and pleural metastases were reduced in HSV-TK30-positive tumors of both cell lines. A significant therapeutic effect in bystander experiments was observed in squamous cell carcinoma. This was correlated with higher expression of connexin-43. CONCLUSIONS: Delivery of HSV-TK30 in a VSV-G pseudotyped retroviral vector and subsequent ganciclovir application provided therapeutic efficacy. Despite of low transduction rates achievable in gene transfer in situ, prodrug therapy appears to be feasible in tumor cells with efficient bystander effects.
