How can radiation cause cells to undergo apoptosis?

Radiation induces apoptosis primarily by causing significant damage to a cell's DNA. When ionizing radiation traverses a cell, it creates chemical alterations that can result in double-stranded breaks within the genetic material.312

The cell's response to this damage is largely regulated by the p53 gene, which acts as a critical sensor for genetic integrity. Under normal conditions, when radiation causes DNA damage, levels of the p53 protein rise. This protein initially halts the cell cycle to allow DNA repair mechanisms to fix the lesions. However, if the genetic damage is too extensive to be repaired, p53 triggers a series of biochemical reactions that force the cell to undergo programmed cell death, or apoptosis.1

In the context of cancer treatment, radiation therapy relies on this mechanism to eliminate malignant cells. Tumors that have lost functional p53 are often more resistant to such therapies because they lack the ability to effectively initiate this self-destruction process.41