Mechanism by which Ionizing Radiation Kills Cancer Cells

Unknown

The primary mechanism by which ionizing radiation induces cell death is:Direct and indirect injury to deoxyribonucleic acid (DNA).
Ionizing radiation can cause:Lethal damage:Damage that cannot be repaired:For example:Most double-strand DNA breaksSublethal damage:Damage that can be repaired if conditions are correct:For example:Most single-strand DNA breaks.
Factors that increase the cell’s ability to repair damage:Make it less sensitive to ionizing radiation.
The cell division cycle is divided into four distinct phases:Replication of DNA occurs in the synthesis (S) phaseNuclear division and cell fission occur in the mitotic (M) phase. The intervals between these two phases are called the gap (G) phases:Cells in M phase (mitosis):Have the least capability to repair sublethal damage:Hence are the most radiation sensitive
- Cells in S phase:Have the most capability of repairing damage:Consequently are the most radiation resistant.
- Resting cells (G0):Are less sensitive to radiation injury than cells that are actively dividing (and proceeding through the cell cycle).
Cancer cells are generally less differentiated (with less ability to repair DNA damage) and more rapidly dividing than normal tissue:The fact that tumor cells are usually more sensitive to radiation than surrounding normal tissue is an important determinant of the utility of radiation therapy.

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Published by Rodrigo Arrangoiz MS, MD, FACS, FSSO