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Relationship between radiation-induced low-dose hypersensitivity and the bystander effect
Carmel Mothersill1, C B Seymour, M C Joiner
1Radiation and Environmental Science Centre, Dublin Institute of Technology, Fitzwilliam House, 30 Upper Pembroke Street, Dublin 2, Ireland. cmothersill@rsc.iol.ie
Radiation Research
|April 23, 2002
Summary
Low doses of ionizing radiation trigger unexpected biological effects. Studies reveal an inverse relationship between the bystander effect and low-dose hyper-radiosensitivity, suggesting distinct underlying mechanisms in radiobiology.
Area of Science:
- Radiobiology
- Cellular Biology
- Radiation Oncology
Background:
- Low doses of ionizing radiation exhibit unexpected biological phenomena.
- These include the bystander effect and low-dose hyper-radiosensitivity/increased radioresistance.
- These effects exceed predictions from conventional DNA repair models.
Purpose of the Study:
- To investigate whether the bystander effect and low-dose hyper-radiosensitivity/increased radioresistance share similar or exclusive mechanisms.
- To explore the relationship between these two phenomena in various cell lines.
Main Methods:
- Utilized 13 cell lines to assess both hyper-radiosensitivity/increased radioresistance and bystander response.
- Employed established protocols and clonogenicity as the endpoint for measuring radiobiological effects.
- Analyzed the dose-response curves and TP53 status of the cell lines.
Main Results:
- Observed significant variation in the expression of both phenomena across cell lines.
- Found an inverse relationship: cell lines with a strong bystander effect did not exhibit hyper-radiosensitivity, and vice versa.
- This inverse relationship was not clearly linked to TP53 status or malignancy.
Conclusions:
- The findings suggest that the bystander effect and low-dose hyper-radiosensitivity/increased radioresistance may operate via distinct mechanisms.
- Cell lines with a wide shoulder in their radiation dose-response curve showed hyper-radiosensitivity and no bystander effect.
- These results may offer new insights into factors governing cell death and survival at low radiation doses.