Molecular Aspects of Human Radiosensitivity

Radiotherapy is a clinical treatment modality where ionizing radiation is used to treat patients with malignant neoplasms. The goal of radiation therapy is to deliver a measured dose of radiation to a defined volume with minimal damage to surrounding normal tissue, resulting in eradication of the tumor. Radiotherapy is generally given in divided doses or fractionated. Molecular biology methods have enhanced our ability to investigate the response of cells to ionizing radiation. These methods can be applied to tissue-culture systems or to biopsies from patients. In one hand to develop a quick and easy way to predict the radiosensitivity of a patient and in the other hand, to understand how do cells respond to stress produced by ionizing radiation? In this review we will mainly explain two major mechanisms involved in human individual radiosensitivity; the DNA-damage repair defect mechanism and the DNA-repair signaling via cell cycle checkpoint defect.