Radiation-induced bystander phenomenon: insight and implications in radiotherapy

Abstract

Despite the extensive utilization of radiotherapy in cancer treatments, clinicians often face challenges in achieving desired outcomes. This is because of the existence of secondary radiation effects like bystander phenomenon that influence radiation nontargeted cells and tissues. The concept of bystander effects of radiation was first proposed in the latter half of the last century which led to a paradigm shift in classical dogma of radiation biology. This review primarily focuses on the diverse mechanisms of bystander signal production and response under the influence of different sources of radiation like α-, β-, γ rays as well as protons and ions. The dependency of bystander effects on cell type and linear energies are also reviewed. Furthermore, the reciprocal effects exerted by bystander cells on radiation-targeted cells have been discussed. Radiation-induced signaling in targeted cells stimulates the release of different mediators that induce a plethora of molecular effects on adjacent unirradiated cells, leading to cell death or proliferation. These responses are regulated by the cell type and linear energies of radiation. Different radiation sources have diverse damaging impacts on bystander cells wherein the complex interplay of signaling molecules, inflammation, apoptosis, necrosis, and autophagy determine the fate of the cells. Further, the feedback mechanism of bystander cells controls the severity of effects in radiation-targeted cells. From the existing literature, it is difficult to speculate how far the fundamental mechanisms of induction of bystander effects by irradiated cancer cells differ from that of normal cells, although cell-specific responses are observed in bystander cells. To have an accurate idea about the actual scenario, consideration of all possible variations of experimental conditions is necessary. This is crucial for optimal utilization of radiotherapy protocols to serve twofold purposes, increase radiotherapy efficiency while causing minimal health risks.

Keywords:

• Bystander response
• rescue effect
• cell type
• LET dependency
• radiotherapy

Disclosure statement

The authors reported no potential conflict of interest.

Additional information

Funding

This work was supported by fellowship from the Indian Council of Medical Research [Award letter No: 3/1/3/JRF-2016/HRD].

Notes on contributors

Sharmi Mukherjee

Sharmi Mukherjee a PhD research scholar of Stress Biology Lab, UGC-DAE Consortium for Scientific Research, Kolkata Centre, India. She has a bachelor’s and master’s degree in Zoology. Her research interests are molecular biology, stress biology, radiation-induced bystander effects, radiation, and cancer.

Anindita Chakraborty

Anindita Chakraborty Scientist G is the Head of Stress Biology Lab at UGC-DAE Consortium for Scientific Research, Kolkata Centre. Her research program focuses on assessment of the stress-effects in cellular processes and functional manifestation of stress exposed life forms in terms of altered metabolism. She has a bachelor’s and master’s degree in Zoology, M. Phil in Environmental Science and PhD in Biochemistry with more than 25 years of research experience devoted to areas of cancer biochemistry, stress biology, and molecular dynamics.