J Korean Soc Microbiol.  1998 Apr;33(2):227-235.

Effect of Retrovirus and p53 Tumor Suppressor Gene in Gene Therapy of Cancer Cells

• Suh SI
• Suh MH
• Baek WK
• Cho JW

Abstract

Cancer is considered to occur through abnormal growth and differentiation processes, in which oncogenes and tumor suppressor genes are deeply related. Cellular responses to DNA-damaging agents are believed to be critical determinants of human tumorigenesis. Cell cycle arrests and DNA repair following DNA damage require the coordination of multiple gene products that, as a whole, serve to maintain the integrity of the genome. Within the cell cycle, both G1-S and G2-M phase transitions are under constant surveillance by checkpoint genes for the protection of cells from either exogenous or endogenous DNA-damaging agents. p53 tumor suppressor gene mediates cell cycle perturbations in response to DNA damage, and play a role in cell death, genetic stability, and cancer susceptibility. Recently, gene therapy with p53 tumor suppressor gene is expected as a new effective therapeutic strategy in many kinds of cancer. By using retroviral vector system, we transduced p53 tumor suppressor gene into human osteosarcoma cells, and analysed its growth suppression and apoptosis inducing effects. Combined effects of p53 gene therapy with chemotherapeutic agent or radiation were also analysed. Titer of ecotrophic p53 retrovirus was 5.0x10/ml, and that of amphotrophic p53 retrovirus was 2.0x10/ml when NIH3T3 cells were used as target cells. Human osteosarcoma cells infected with amphotrophic p53 retroviruses showed increased p21waf1 gene expression, which acts as a major cyclin-dependent kinase inhibitor in DNA damage responses. In normal DMEM media, human skin fibroblasts infected with amphotrophic p53wt retroviruses showed very slow growing (1.7 fold increase in doubling time) and very low saturation density (50% decrease in cell density). In media containing chemotherapeutic agent, human osteosarcoma cells infected with p53wt retroviruses died rapidly; 75% of them died within 4 days and all of them died within 10 days of incubation with chemotherapeutic agent. Their DNAs were extracted and electrophoresed in agarose gel, and we identified DNA ladders characteristic of apoptotic cell death. When human osteosarcoma cells infected with p53 retroviruses were irradiated with ultraviolet light, more than 95% of cancer cells died within 1 day; whereas mock infected cells showed only less than 5% of cell death. These findings suggest that retroviral vector mediated p53 tumor suppressor gene transfer into cancer cells can suppress tumor cell growth and decrease tumor cell density effectively. These findings also suggest that effective induction of tumor cell apoptosis can be obtained when p53 gene therapy is used in combination with chemotherapy or radiotherapy.

MeSH Terms

Apoptosis
Carcinogenesis
Cell Count
Cell Cycle
Cell Cycle Checkpoints
Cell Death
DNA
DNA Damage
DNA Repair
Drug Therapy
Fibroblasts
Gene Expression
Genes, p53
Genes, Tumor Suppressor*
Genetic Therapy*
Genome
Humans
Oncogenes
Osteosarcoma
Phase Transition
Phosphotransferases
Radiotherapy
Retroviridae*
Sepharose
Skin
Ultraviolet Rays
Zidovudine
DNA
Phosphotransferases
Sepharose
Zidovudine