Radiation-induced Non-targeted Effect and Carcinogenesis; Implications in Clinical Radiotherapy

Abstract

Bystander or non-targeted effect is known to be an interesting phenomenon in radiobiology. The genetic consequences of bystander effect on non-irradiated cells have shown that this phenomenon can be considered as one of the most important factors involved in secondary cancer after exposure to ionizing radiation. Every year, millions of people around the world undergo radiotherapy in order to cure different types of cancers. The most crucial aim of radiotherapy is to improve treatment efficiency by reducing early and late effects of exposure to clinical doses of radiation. Secondary cancer induction resulted from exposure to high doses of radiation during treatment can reduce the effectiveness of this modality for cancer treatment. The perception of carcinogenesis risk of bystander effects and factors involved in this phenomenon might help reduce secondary cancer incidence years after radiotherapy. Different modalities such as radiation LET, dose and dose rate, fractionation, types of tissue, gender of patients, etc. may be involved in carcinogenesis risk of bystander effects. Therefore, selecting an appropriate treatment modality may improve cost-effectiveness of radiation therapy as well as the quality of life in survived patients. In this review, we first focus on the carcinogenesis evidence of non-targeted effects in radiotherapy and then review physical and biological factors that may influence the risk of secondary cancer induced by this phenomenon.

Apelin+ Endothelial Niche Cells Control Hematopoiesis and Mediate Vascular Regeneration after Myeloablative Injury

“…Irradiation and 5-FU treatment target multiple cell types (Maxwell et al, 2003;Yahyapour et al, 2018). As BM hematopoietic cells are largely eliminated after irradiation and chemotherapy, we reasoned that this loss might be a key contributor to the observed vascular defects.…”

Radiation-Induced Normal Tissue Damage: Oxidative Stress and Epigenetic Mechanisms

“…It can also activate signal transduction pathways and early-response transcription factors [5]. The redox system plays an important role in acute radiation damage and is responsible for some radiation-induced early and late effects including inflammation, out-of-field effects, fibrosis, bystander effects, and others [6–9].…”

Radiation Protection and Mitigation by Natural Antioxidants and Flavonoids: Implications to Radiotherapy and Radiation Disasters

“…Results of several experiments have shown that cell metabolism and inflammatory responses following exposure to radiation play a key role in continuous free radical production and disruption of normal organ functions [6][7][8][9]. Attenuation of oxidative damage and inflammation following exposure to ionizing radiation can alleviate damage to radiosensitive organs, leading to increased survival [10,11].…”