Effects of cell cycle phase on low-dose hyper-radiosensitivity.

Area of Science:

• Oncology
• Radiation Biology
• Cell Biology

Background:

• Low-dose radiation exposure can induce complex cellular responses.
• Hyper-radiosensitivity (HRS) is a phenomenon where cells exhibit increased sensitivity to low radiation doses.
• Understanding cell-cycle-dependent radiation response is crucial for optimizing radiotherapy.

Purpose of the Study:

• To investigate the low-dose radiation response of human glioma cell lines across different cell-cycle phases.
• To determine if hyper-radiosensitivity (HRS) varies based on cell-cycle position.
• To assess the impact of cell-cycle effects on predictions for multiple low-dose radiation regimens.

Main Methods:

• Clonogenic survival assays were performed on G1, G2, and S phase human glioma cells (T98G and U373).
• Cell populations were separated using fluorescence-activated cell sorting.
• Irradiation was conducted using 240 kVp X-rays at doses ranging from 0.05 to 5 Gy.
• Cell-survival data were analyzed using linear-quadratic and induced-repair models.

Main Results:

• Both cell lines showed altered low-dose responses when cell populations were separated by phase.
• T98G cells exhibited HRS in all phases, most prominently in G2.
• U373 cells demonstrated HRS exclusively in the G2 phase.

Conclusions:

• Hyper-radiosensitivity (HRS) is predominantly a G2 phase cell response in human glioma cells.
• The observed HRS in asynchronous populations is largely driven by the G2 population.
• Actively proliferating (G2-rich) cell populations may exhibit greater radiosensitivity to very low radiation doses compared to quiescent populations.