Induced radioresistance: an overview and historical perspective

Area of Science:

• Radiobiology
• Cellular Biology
• Molecular Biology

Background:

• Cellular mechanisms for radioprotection exist and are upregulated by low-dose ionizing radiation.
• These induced mechanisms can manifest as protection against subsequent higher radiation doses or altered cellular responses to radiation.
• Evidence spans various organisms, including yeast, bacteria, plants, insects, and mammalian/human cells, both in vitro and in vivo.

Purpose of the Study:

• To summarize the evidence for induced cellular radioprotective mechanisms.
• To describe the dual modes of action for these induced mechanisms.
• To highlight the rapid cellular responses observed following DNA-damaging agent exposure.

Main Methods:

• Review of existing scientific literature on cellular responses to ionizing radiation and DNA-damaging agents.
• Analysis of studies across diverse biological systems (microorganisms, plants, insects, mammals, human cells).
• Examination of in vitro and in vivo experimental models.

Main Results:

• Induced radioprotection observed in yeast, bacteria, protozoa, algae, higher plant cells, insect cells, mammalian cells, human cells, and animal models.
• Two modes of induced radioprotection identified: protection against subsequent larger doses and altered dose-response relationships.
• Rapid cellular changes, including altered protein levels and gene expression, occur within minutes to hours after exposure.

Conclusions:

• Cellular radioprotective mechanisms are upregulated by low-dose radiation and DNA-damaging agents.
• The precise molecular mechanisms underlying induced radioresistance, such as repair or cell-cycle control, require further definition.
• The rapid nature of these cellular responses suggests a significant role in induced radioresistance.