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The in vivo clearance of Ha-ras transformants by natural killer cells
P W Johnson1, J Stankova, D Dexter
1Department of Immunology, University of Toronto, Ontario, Canada.
Abstract:
The experiments in this study were designed to test the hypothesis that natural killer (NK) cells play a role in host surveillance against early neoplastic changes in the malignant process. C3H 10T1/2 mouse fibroblasts were transfected with a pSV2-neo plasmid vector which contains EJ, the mutated c-Ha-ras, regulated by its own promoter. Control cells were transfected with pSV2-neo alone and did not contain the ras gene. Oncogene-transfected cells were compared with control cells for lung colony formation following tail vein injection into C3H mice. Intravenous injection of ras-transfected 10T1/2 cells induced marked lung colony formation in vivo, whereas C3H 10T1/2 parental lines or 10T1/2 cells transfected with pSV2-neo alone induced no lung colonies in C3H mice. The colonising potential of ras transfectants could be decreased by augmentation of NK activity by injection of polyinosinic cytidylic acid and increased by depletion of NK effectors with anti-asialo GM1. Experiments with beige mice demonstrated that the mortality of syngeneic, NK-deficient C3H-bg/bg mice injected with ras tranfectants was significantly greater than similarly treated NK-normal C3H(-)+/bg littermate controls. The results support the view that NK cells are capable in vivo of recognizing early defined stages in the neoplastic process initiated by oncogenes.
Insights
Natural killer (NK) cells surveil against early cancer. This study shows NK cells prevent tumor formation in mice, highlighting their role in host defense against oncogene-induced neoplasia.
Area of Science:
- Immunology
- Oncology
- Cell Biology
Background:
- Natural killer (NK) cells are crucial for innate immunity and tumor surveillance.
- Early neoplastic changes are a target for immune system intervention.
- Oncogenes drive cellular transformation and cancer development.
Purpose of the Study:
- To investigate the role of NK cells in recognizing and eliminating early neoplastic changes induced by oncogenes.
- To determine if NK cell activity influences the in vivo progression of oncogene-transformed cells.
Main Methods:
- Transfection of C3H 10T1/2 mouse fibroblasts with a mutated c-Ha-ras oncogene.
- Comparison of lung colony formation in mice injected with oncogene-transfected cells versus control cells.
- Modulation of NK cell activity using polyinosinic cytidylic acid and anti-asialo GM1 antibody.
- Assessment of tumor progression in NK-deficient beige mice.
Main Results:
- Intravenous injection of ras-transfected cells led to significant lung colony formation in vivo.
- NK cell augmentation reduced colonizing potential, while NK cell depletion increased it.
- Mortality was significantly higher in NK-deficient beige mice injected with ras transfectants compared to NK-normal controls.
- These findings demonstrate NK cells' ability to recognize and control early oncogene-induced neoplastic lesions.
Conclusions:
- NK cells play a significant role in host surveillance against early neoplastic transformations.
- The study provides in vivo evidence for NK cell-mediated control of oncogene-initiated malignancy.
- NK cells are critical effectors in preventing the progression of early-stage cancers.
