Radiation induced non-targeted response: mechanism and potential clinical implications.
ABSTRACT Generations of students in radiation biology have been taught that heritable biological effects require direct damage to DNA. Radiation-induced non-targeted/bystander effects represent a paradigm shift in our understanding of the radiobiological effects of ionizing radiation in that extranuclear and extracellular effects may also contribute to the biological consequences of exposure to low doses of radiation. Although radiation induced bystander effects have been well documented in a variety of biological systems, including 3D human tissue samples and whole organisms, the mechanism is not known. There is recent evidence that the NF-κB-dependent gene expression of interleukin 8, interleukin 6, cyclooxygenase-2, tumor necrosis factor and interleukin 33 in directly irradiated cells produced the cytokines and prostaglandin E2 with autocrine/paracrine functions, which further activated signaling pathways and induced NF-κB-dependent gene expression in bystander cells. The observations that heritable DNA alterations can be propagated to cells many generations after radiation exposure and that bystander cells exhibit genomic instability in ways similar to directly hit cells indicate that the low dose radiation response is a complex interplay of various modulating factors. The potential implication of the non-targeted response in radiation induced secondary cancer is discussed. A better understanding of the mechanism of the non-targeted effects will be invaluable to assess its clinical relevance and ways in which the bystander phenomenon can be manipulated to increase therapeutic gain in radiotherapy.
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ABSTRACT: Cancer therapy makes patients sick. The therapies that are available to clinicians allow them to successfully control nausea, emesis and pain. However, this is not the case for a number of other symptoms that include fatigue, distractibility, poor memory, and diminished interest in previously pleasurable activities. These symptoms cluster during the course of cancer therapy and impair patient quality of life, limit therapy options and do not always resolve at the cessation of treatment. It is possible to describe the intensity and temporal features of symptoms and assess their relationship with the inflammatory response that is associated with cancer and cancer therapy. At the preclinical level, sophisticated animal models still need to be deployed to study the causal role of inflammation in specific components of cancer-related symptoms. Various approaches can be optimally combined in a translational symptom research pathway to provide a framework for assessing in a systematic manner the neurobehavioral toxicity of existing and newly developed cancer therapies. Ultimately, this knowledge will allow derivation of mechanism-based interventions to prevent or alleviate cancer-related symptoms.Nature Reviews Clinical Oncology 05/2012; 9(7):414-26. · 11.96 Impact Factor