PURPOSE: Selective introduction of genes conferring chemosensitivity into proliferating tumor cells may be used to treat cancer. We first investigated the bystander effect of retrovirus-mediated gene transfer of herpes simplex virus thymidine kinase(HSV-TK) gene to murine neuroblstoma cell line(neuro-2a) in vitro and in vivo. Second, we examined the mechanism and its enhancement of the bystander effect in murine neuroblastoma. METHODS: To investigate the bystander effect, we studied tumor growth and survival time after HSV-TK/ganciclovir(GCV) treatment in a syngenic A/J mouse neuroblastoma model by mixing various ratios of HSV-TK-expressing neuro-2a cells with wild type neuro-2a cells followed by GCV treatment. To investigate the mechanism of the bystander effect in murine neuroblastoma, immunohistochemistry using connexin 43, CD4 and CD8-specific monoclonal antibodies was analyzed. We studied whether IL-2-secreting neuro-2a cells(neuro-2a/IL-2) would potentiate the bystander effect. RESULTS: A strong bystander effect was observed in vitro and in vivo. The bystander effect in murine neuroblastoma was dependent on the immune response rather than connexin-mediated gap junction. Neuro-2a/IL-2 treatment enhanced the bystander effect in the HSV-TK/GCV system in murine neuroblastoma model. CONCLUSION: We conclude that the bystander effect in murine neuroblastoma depends on immune response and is enhanced by neuro-2a/IL-2.
Animals ; Antibodies, Monoclonal ; Bystander Effect* ; Connexin 43 ; Gap Junctions ; Genetic Therapy* ; Immunohistochemistry ; Mice ; Neuroblastoma* ; Simplexvirus ; Thymidine

No abstract available.
Bystander Effect* ; Carcinoma, Hepatocellular* ; Cell Line* ; Ganciclovir* ; Herpes Simplex* ; Phosphotransferases* ; Simplexvirus*

PURPOSE: To demonstrate the bystander effect in murine neuroblastoma model which transduced with HSV-TK gene in vitro and in vivo. METHODS: The LNC/TK vector was transfered in vitro into the neuro-2a cells, murine neuroblastoma cell line. Variable mixed populations of neuro-2a cells consisting of HSV-TK+ or HSV-TK- were plated into culture plates and treated with GCV for another 4 days. Surviving cells were counted and cell viability was determinated. For investigating the in vivo bystander effect, variable mixed populations of neuro-2a cells consisting of HSV-TK+ and HSV-TK- were inoculated into A/J mice. The tumor size was measured following injection of GCV for 7 days. RESULTS: The survival rate of the 100% neuro-2a/TK group was 90%, 25%, 5% and 0%, of 50% neuro-2a/TK group was 92%, 30%, 10% and 0%, and of the 10% neuro-2a/TK group was 95%, 40%, 15% and 5%. But, the survival rate of 0% neuro-2a/TK group was 120%, 150%, 180% and 220% on days 1, 2, 3, and 4 respectively. In the 100% and 50% neuro-2a/TK groups, tumor had disappeared following administration of GCV and in 10% neuro-2a/TK group, tumor size was not increased during GCV treatment. In 0% neuro-2a/TK group, tumor size increased during administration of GCV and all mice died after 6 weeks. CONCLUSIONS: We demonstrated the bystander effect in a murine neuroblastoma model which transduced with HSV-TK gene in vitro and in vivo. These results suggest that HSV-TK/GCV gene therapy may be useful for treatment of neuroblastoma.
Animals ; Bystander Effect* ; Cell Line ; Cell Survival ; Genetic Therapy* ; Mice ; Neuroblastoma* ; Survival Rate

Transduction of retroviral-mediated herpes simplex virus thymidine kinase(HSVtk) gene into tumor cells and subsequent ganciclovir(GCV) treatment have been used as an experimental and clinical therapeutic strategy. Because non-transduced tumor cells can be killed by small proportion of transduced cells, known as bystander effect. Increasing bystander effect is useful strategy of suicidal gene therapy using HSVtk gene. To get a better bystander effect, we transduced T98G gliobastoma cells with HSVtk gene, single and double transduction with different marker genes respectively. Double HSVtk gene transduced cell lines showed significantly increased HSVtk activity(83%) by measuring the intracellular amount of phosphrylated 3H-GCV comparing to the single HSVtk gene transduced cell lines. In vitro bystander effect, examined by coculturing with HSVtk gene transduced cells and HSVtk- negative pa rental cells, was significantly increased on double HSVtk gene transduced cell lines. These results suggest that increasing herpes simplex virus thymidine kinase activity by double transfer of HSVtk gene into tumor cells can be a useful strategy for treating cancer with suicidal gene therapy.
Bystander Effect* ; Cell Line ; Ganciclovir ; Genetic Therapy ; Simplexvirus ; Thymidine Kinase* ; Thymidine*

PURPOSE: Gap junction intercellular communication(GJIC) is an important mechanism of the bystander effect in herpes simplex thymidine kinase/ganciclovir(HSVtk/GCV) gene therapy Therefore, we attempted to enhance the bystander effect in vitro by exogenous overexpressing connexin 37(Cx37) in cells to increase GJIC. METHODS: NIH3T3 cells were transfected with the Cx37 and HSVtk gene or the HSVtk gene alone by the calcium phosphate method, and we detected their expression from these cells by RT-PCR. GCV-mediated cytotoxicity and the bystander effect of each transfectant was then assessed and compared. RESULTS: Cells transfected with HSVtk became sensitive to low concentration of GCV. We found significantly increased cytotoxicity in HSVtk/GCV gene therapy after introduction of the HSVtk and Cx37 genes together compared with the cytotoxicity seen after introduction of the HSVtk gene in vitro. Co-expression of the HSVtk and Cx37 genes potentiates HSVtk/GCV gene therapy through the bystander effect. CONCLUSION: These results indicated that the increase of GJIC using Cx37 have potentiated the by stander effect of HSVtk/GCV therapy, and may be a new approach to improve response in suicidal cancer gene therapy.
Bystander Effect* ; Calcium ; Gap Junctions* ; Genes, Neoplasm ; Genetic Therapy* ; Herpes Simplex ; Thymidine

BACKGROUND: Metabolic cooperation via gap junctional intercellular communication (GJIC) is an important mechanism of the bystander effect in gene therapy using the Herpes Simplex Virus thymidine kinase/ganciclovir (HSVtk) 'prodrug' system. Since retinoids have been reported to increase GJIC by induction of connexin 43 expression, we hypothesized that treatment of tumor cells with retinoic acid could augment the bystander erect of the HSVtk/GCV system and result in improved tumor cell killing by enhancing GJIC. METHODS: We transferred HSVtk gene to SKHep-J cell line that does not express connexin43, and also transferred the gone to human and murine mesothelioma cell lines that express connexin43. We verified that retinoic acid enhanced GJIC utilizing a functional double-dye transfer study and evaluated the effects of retinoic acid on the growth rate of honor cells. We then tested the effects of retinoic acid on bystander-mediated cell killing. RESULTS: Addition of all-trans retinoic acid (RA) increased GJIC in cell lines expressing connexin43 and was associated with more efficient in vitro bystander killing in cells transduced with HSVtk via adenoviral and retroviral vectors. In contrast, there was no increase in the efficiency of the bystander effect after exposure to RA in a cell line which had no detectable connexin 43. CONCLUSION: These results provide evidence that retinoids can augment the efficiency of cell killing with the HSVtk/GCV system by enhancing bystander effect and may thus be a promising new approach to improve responses in gene therapy utilizing the HSVtk system to treat tumors.
Bystander Effect* ; Cell Line ; Connexin 43 ; Genetic Therapy* ; Herpes Simplex* ; Homicide ; Humans ; Mesothelioma ; Phosphotransferases* ; Retinoids ; Simplexvirus* ; Thymidine ; Tretinoin* ; Zidovudine

OBJECTIVE: The bystander effect, the phenomenon that non-transduced tumor cells can be killed along with the transduced cells, enables suicidal gene therapy feasible in spite of low efficiency of gene transfer at present time. Increment of thymidine kinase activity in the cells through double copy insertion of HSVtk gene may lead to increased bystander effect in vitro and in vivo, therefore enhancing the therapeutic potential of suicidal gene therapy. To examnine this hypothesis, we did an experiment to improve bystander effect by using double transfer of HSVtk gene into 9L tuomr cells. METHODS: We transduced 9L glioblastoma cells which had one copy or two copies of HSVtk gene using retroviral vector. Two different retroviral vector plasmids containing HSVtk gene were made employing pBabePuro or LXSN plasmid whose selection markers were puromycin and G418, respectively(LtkSP and LtkSN). Recombinant retrovirus was produced from ecotrophic PA317 packaging cells. Infection of the 9L cells with LtkSP recombinant retrovirus and selection with puromycin was done in vitro to make 9L/LtkSP(9LtkS). These cells were infected again with LtkSN recombinant retrovirus and selected under G418 to establish cells containing two copies of HSVtk gene, 9L/LtkSP/ LtkSN(9LtkD). RESULTS: By measuring the intracellular amount of phosphorylated 3H-GCV, 9LtkD cell lines showed significantly increased HSVtk activity, being 70% higher than that of 9LtkS cell lines. The sensitivity to GCV was also markedly increased. In vitro bystander effect, examined by coculturing with HSVtk gene transduced cells and 9L cells, was significantly increased on 9LtkD cell lines. To evaluate the in vivo bystander effect, 9LtkD/9L(20%:80%) cells or 9LtkS/9L (20%:80%) cells were implanted into the brains of Fisher 344 inbred rats, followed by administration of ganciclovir. Rats implanted with 9LtkD/9L cells showed better tumor regression and longer survival than those of 9LtkS/9L after treatment with ganciclovir. CONCLUSION: These results suggest that increasing herpes simplex virus thymidine kinase activity by introducing double copy of HSVtk gene into tumor cells would improve in vitro and in vivo bystander effect, and lead to enhanced efficacy of suicidal gene therapy.
Animals ; Brain ; Bystander Effect* ; Cell Line ; Ganciclovir ; Genetic Therapy ; Glioblastoma ; Glioma ; Herpes Simplex* ; Phosphotransferases* ; Plasmids ; Product Packaging ; Puromycin ; Rats ; Retroviridae ; Simplexvirus* ; Thymidine Kinase ; Zidovudine

PURPOSE: Among cancer gene therapies, the aims to eliminate malignant cells using genes as drugs as substitutes for conventional therapy, the use of bacterial cytosine deaminase (CD) which can convert the nontoxic 5-fluorocytosine (5-FC) to toxic 5-fluorouracil (5-FU), has been reported to provide a useful system for the selective killing of gene- modified mammalian tumor cells. Recently the transfection and expression of the CD gene, and the toxicity of 5-FC in eukaryotic cells, have been reported in colon, prostate and breast cancers, as well as in glioblastomas. To evaluate the growth inhibition effects in WiDr and LoVo colorectal cancer cells, after CD gene transfection and 5-FC administration, for the selective killing of cancer cells. METHODS: WiDr and LoVo colon cancer cell lines were cultured and the absorbencies for the percentage survival, on days 2, 4, 6, 8, and 10 of the culture, estimated by the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetra-zolium bromide (MTT) test. The experimental subjects were divided as follows; Group 1: administration of 5-FC only, Group 2: administration of 5-FU only, Group 3: administration of 5-FC after CD gene transfection using pCMV/CD-1 plasmid vector. Each experiment, on days 2, 4, 6, 8 and 10 of the culture after the administration of 5-FC or 5-FU concentration of 10, 100 and 1000 uM, was triplicated and calculated the mean with standard deviation. The bacterial CD gene was transfected into each cell lines, using the lipofectin method, and the transfection and expression of the CD protein identified with beta-galactosidase immunohistochemical staining and western blotting. The growth inhibition effects in group 3 were compared with those in group 1 and 2, and the bystander effects and cell recoveries, after finishing the 5-FC treatment, evaluated until day 20 of the culture. RESULTS: The calculated survival percentages by from the MTT tests in the WiDr and LoVo cells revealed 110~150% enhancing effects after the administration of 5-FC concentration of 10, 100 and 1000micro M (group 1), and 30~90% after the administration of 5-FU at the same concentrations (group 2), which were shown to be statistically significantly (P<0.001). After transfection of pCMV/CD-1 plasmid vector into the WiDr and LoVo cells using the lipofectin method, the transfection rate of the WiDr and LoVo cells were 4.2 +/- 0.6% and 13.8 +/- 0.8%, respectively. Also the CD protein, with the polyclonal anti-CD antibody, by western blot, revealed weak expression on day 2, followed by strong expression on day 4, which progressively decreased by days 6 and 8 in the WiDr cells. Conversely, the LoVo cells showed weak expression on day 2, which progressively increased by days 4 and 6, was followed by the strongest expression on day 8 in LoVo cells. About 60~85% significant growth inhibition effects (P<0.001) were revealed in group 3, with proportionally different effects, corresponding to the CD gene transfection rate, concentration of 5-FC and duration of the culture. The 60~85% growth inhibition effects were complex of the response to the transfection rate and the bystander effects of CD expressed cells to the CD non-expressed cells. CONCLUSION: From our results, the administration of 5-FC after CD gene transfection revealed statistically significant growth inhibition effects of 60~85%, which were complex of the effects of CD expressed cells and the bystander effects to the CD non-expressed cells, and proportionally corresponding to the transfection rate, the duration of the CD protein expression and the concentration of 5-FC.
beta-Galactosidase ; Blotting, Western ; Breast ; Bystander Effect ; Cell Line* ; Colon* ; Colonic Neoplasms* ; Colorectal Neoplasms ; Cytosine Deaminase* ; Cytosine* ; Eukaryotic Cells ; Flucytosine* ; Fluorouracil ; Genes, Neoplasm ; Glioblastoma ; Homicide* ; Plasmids ; Prostate ; Transfection*

PURPOSE: Among cancer gene therapies, the aims to eliminate malignant cells using genes as drugs as substitutes for conventional therapy, the use of bacterial cytosine deaminase (CD) which can convert the nontoxic 5-fluorocytosine (5-FC) to toxic 5-fluorouracil (5-FU), has been reported to provide a useful system for the selective killing of gene- modified mammalian tumor cells. Recently the transfection and expression of the CD gene, and the toxicity of 5-FC in eukaryotic cells, have been reported in colon, prostate and breast cancers, as well as in glioblastomas. To evaluate the growth inhibition effects in WiDr and LoVo colorectal cancer cells, after CD gene transfection and 5-FC administration, for the selective killing of cancer cells. METHODS: WiDr and LoVo colon cancer cell lines were cultured and the absorbencies for the percentage survival, on days 2, 4, 6, 8, and 10 of the culture, estimated by the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetra-zolium bromide (MTT) test. The experimental subjects were divided as follows; Group 1: administration of 5-FC only, Group 2: administration of 5-FU only, Group 3: administration of 5-FC after CD gene transfection using pCMV/CD-1 plasmid vector. Each experiment, on days 2, 4, 6, 8 and 10 of the culture after the administration of 5-FC or 5-FU concentration of 10, 100 and 1000 uM, was triplicated and calculated the mean with standard deviation. The bacterial CD gene was transfected into each cell lines, using the lipofectin method, and the transfection and expression of the CD protein identified with beta-galactosidase immunohistochemical staining and western blotting. The growth inhibition effects in group 3 were compared with those in group 1 and 2, and the bystander effects and cell recoveries, after finishing the 5-FC treatment, evaluated until day 20 of the culture. RESULTS: The calculated survival percentages by from the MTT tests in the WiDr and LoVo cells revealed 110~150% enhancing effects after the administration of 5-FC concentration of 10, 100 and 1000micro M (group 1), and 30~90% after the administration of 5-FU at the same concentrations (group 2), which were shown to be statistically significantly (P<0.001). After transfection of pCMV/CD-1 plasmid vector into the WiDr and LoVo cells using the lipofectin method, the transfection rate of the WiDr and LoVo cells were 4.2 +/- 0.6% and 13.8 +/- 0.8%, respectively. Also the CD protein, with the polyclonal anti-CD antibody, by western blot, revealed weak expression on day 2, followed by strong expression on day 4, which progressively decreased by days 6 and 8 in the WiDr cells. Conversely, the LoVo cells showed weak expression on day 2, which progressively increased by days 4 and 6, was followed by the strongest expression on day 8 in LoVo cells. About 60~85% significant growth inhibition effects (P<0.001) were revealed in group 3, with proportionally different effects, corresponding to the CD gene transfection rate, concentration of 5-FC and duration of the culture. The 60~85% growth inhibition effects were complex of the response to the transfection rate and the bystander effects of CD expressed cells to the CD non-expressed cells. CONCLUSION: From our results, the administration of 5-FC after CD gene transfection revealed statistically significant growth inhibition effects of 60~85%, which were complex of the effects of CD expressed cells and the bystander effects to the CD non-expressed cells, and proportionally corresponding to the transfection rate, the duration of the CD protein expression and the concentration of 5-FC.
beta-Galactosidase ; Blotting, Western ; Breast ; Bystander Effect ; Cell Line* ; Colon* ; Colonic Neoplasms* ; Colorectal Neoplasms ; Cytosine Deaminase* ; Cytosine* ; Eukaryotic Cells ; Flucytosine* ; Fluorouracil ; Genes, Neoplasm ; Glioblastoma ; Homicide* ; Plasmids ; Prostate ; Transfection*

PURPOSE: Metabolic cooperation via gap junctional intercellular communication (GJIC) is an important mechanism of the bystander effect in gene therapy using the Herpes Simplex Virus thymidine kinase/ganciclovir (HSVtk/GCV) "prodrug" system. Since retinoids have been reported to increase GJIC by induction of connexin expression, we hypothesized that these compound could be used to augment the HSVtk/GCV bystander effect. MATERIALS AND METHODS: We transferred HSVtk gene to AB12 cell line that express connexin43 as a component of gap junction. We examined the effects of retinoic acid (RA) on GJIC utilizing a functional double-dye transfer study. To evaluate the bystander effect in vivo, a murine subcutaneous tumor model was established. Before proceeding with comparisons of HSVtk/GCV mediated bystander cell killing, we evaluated the effects of RA on flank tumor growth in order to rule out a potential antitumor effect of RA alone. Then we determined the effects of retinoic acid on bystander-mediated cell killing in an animal model. RESULTS: Addition of all-trans retinoic acid increased GJIC in AB12 cell line and was associated with more efficient GCV induced bystander killing in animal model. HSVtk transduced tumors in mice treated with the combination of GCV and retinoids were significantly smaller than those treated with GCV or retinoids alone. CONCLUSION: These results provide evidence that retinoids can augment the efficiency of cell killing with the HSVtk/GCV system by enhancing bystander effects and may thus be a promising new approach to improve response in gene therapy utilizing the HSVtk/GCV system to treat tumors.
Animals ; Bystander Effect ; Cell Line ; Connexin 43 ; Gap Junctions ; Genetic Therapy* ; Herpes Simplex* ; Homicide ; Mice ; Models, Animal ; Phosphotransferases* ; Retinoids ; Simplexvirus* ; Thymidine ; Tretinoin*