Carcinogenesis from inhaled (239)PuO(2) in beagles: Evidence for radiation homeostasis at low doses?

Structural and temporal dynamics analysis on immune response in low-dose radiation: History, research hotspots and emerging trends

BACKGROUND

Radiotherapy (RT) is a cornerstone of cancer treatment. Compared with conventional high-dose radiation, low-dose radiation (LDR) causes less damage to normal tissues while potentially modulating immune responses and inhibiting tumor growth. LDR stimulates both innate and adaptive immunity, enhancing the activity of natural killer cells, dendritic cells, and T cells. However, the mechanisms underlying the effects of LDR on the immune system remain unclear.

AIM

To explore the history, research hotspots, and emerging trends in immune response to LDR literature over the past two decades.

METHODS

Publications on immune responses to LDR were retrieved from the Web of Science Core Collection. Bibliometric tools, including CiteSpace and HistCite, were used to identify historical features, active topics, and emerging trends in this field.

RESULTS

Analysis of 1244 publications over the past two decades revealed a significant surge in research on immune responses to LDR, particularly in the last decade. Key journals such as INR J Radiat Biol, Cancers, and Radiat Res published pivotal studies. Citation networks identified key studies by authors like Twyman-Saint Victor C (2015) and Vanpouille-Box C (2017). Keyword analysis revealed hotspots such as ipilimumab, stereotactic body RT, and targeted therapy, possibly identifying future research directions. Temporal variations in keyword clusters and alluvial flow maps illustrate the evolution of research themes over time.

CONCLUSION

This bibliometric analysis provides valuable insights into the evolution of studies on responses to LDR, highlights research trends, and identifies emerging areas for further investigation.

The Hormesis Concept: Strengths and Shortcomings

Hormesis implies that the effects of various materials or conditions that organisms are exposed to, may not have linear dose-response characteristics but rather, can be biphasic. Thus the response to a low dose of a stressor may be the opposite to that occurring at higher doses. Such a dual response is postulated for many toxicants and physical conditions and may involve a beneficial adaptive response. Such a non-linear effect is undoubtedly present in many useful pharmacological and nutraceutical agents with can be toxic at high concentrations. This somewhat divisive topic is an area of study that should be objectively studied and not clouded by political and policy considerations. The objective of this review is to examine claims concerning those exposures where hormesis seems to exist and also those where there is no good supporting evidence. The breadth of this phenomenon and potential mechanisms underlying hormetic events are discussed together with their limitations.

Low Dose and Non-Targeted Radiation Effects in Environmental Protection and Medicine-A New Model Focusing on Electromagnetic Signaling

The role of signalling in initiating and perpetuating effects triggered by deposition of ionising radiation energy in parts of a system is very clear. Less clear are the very early steps involved in converting energy to chemical and biological effects in non-targeted parts of the system. The paper aims to present a new model, which could aid our understanding of the role of low dose effects in determining ultimate disease outcomes. We propose a key role for electromagnetic signals resulting from physico-chemical processes such as excitation decay, and acoustic waves. These lead to the initiation of damage response pathways such as elevation of reactive oxygen species and membrane associated changes in key ion channels. Critically, these signalling pathways allow coordination of responses across system levels. For example, depending on how these perturbations are transduced, adverse or beneficial outcomes may predominate. We suggest that by appreciating the importance of signalling and communication between multiple levels of organisation, a unified theory could emerge. This would allow the development of models incorporating time, space and system level to position data in appropriate areas of a multidimensional domain. We propose the use of the term "infosome" to capture the nature of radiation-induced communication systems which include physical as well as chemical signals. We have named our model "the variable response model" or "VRM" which allows for multiple outcomes following exposure to low doses or to signals from low dose irradiated cells, tissues or organisms. We suggest that the use of both dose and infosome in radiation protection might open up new conceptual avenues that could allow intrinsic uncertainty to be embraced within a holistic protection framework.

The effects of ionizing radiation on domestic dogs: a review of the atomic bomb testing era

Dogs were frequently employed as laboratory subjects during the era of atomic bomb testing (1950–1980), particularly in studies used to generate predictive data regarding the expected effects of accidental human occupational exposure to radiation. The bulk of these studies were only partly reported in the primary literature, despite providing vital information regarding the effects of radiation exposure on a model mammalian species. Herein we review this literature and summarize the biological effects in relation to the isotopes used and the method of radionuclide exposure. Overall, these studies demonstrate the wide range of developmental and physiological effects of exposure to radiation and radionuclides in a mid‐sized mammal.

Cancer immunotherapy: how low-level ionizing radiation can play a key role

The cancer immunoediting hypothesis assumes that the immune system guards the host against the incipient cancer, but also "edits" the immunogenicity of surviving neoplastic cells and supports remodeling of tumor microenvironment towards an immunosuppressive and pro-neoplastic state. Local irradiation of tumors during standard radiotherapy, by killing neoplastic cells and generating inflammation, stimulates anti-cancer immunity and/or partially reverses cancer-promoting immunosuppression. These effects are induced by moderate (0.1-2.0 Gy) or high (>2 Gy) doses of ionizing radiation which can also harm normal tissues, impede immune functions, and increase the risk of secondary neoplasms. In contrast, such complications do not occur with exposures to low doses (≤0.1 Gy for acute irradiation or ≤0.1 mGy/min dose rate for chronic exposures) of low-LET ionizing radiation. Furthermore, considerable evidence indicates that such low-level radiation (LLR) exposures retard the development of neoplasms in humans and experimental animals. Here, we review immunosuppressive mechanisms induced by growing tumors as well as immunomodulatory effects of LLR evidently or likely associated with cancer-inhibiting outcomes of such exposures. We also offer suggestions how LLR may restore and/or stimulate effective anti-tumor immunity during the more advanced stages of carcinogenesis. We postulate that, based on epidemiological and experimental data amassed over the last few decades, whole- or half-body irradiations with LLR should be systematically examined for its potential to be a viable immunotherapeutic treatment option for patients with systemic cancer.

Threshold for Radon-Induced Lung Cancer From Inhaled Plutonium Data

Cohen's lung cancer mortality data, from his test of the LNT theory, do not extend to the no observed adverse effects level (NOAEL) above which inhaled radon decay products begin to induce excess lung cancer mortality. Since there is concern about the level of radon in homes, it is important to set the radon limit near the NOAEL to avoid the risk of losing a health benefit. Assuming that dogs model humans, data from a study on inhaled plutonium dioxide particulates in dogs were assessed, and the NOAEL for radon-induced lung tumors was estimated to be about 2100 Bq/m(3). The US Environmental Protection Agency should consider raising its radon action level from 150 to at least 1000 Bq/m(3).

Commentary on Inhaled (239)PUO2 in Dogs - A Prophylaxis Against Lung Cancer?

Several studies on the effect of inhaled plutonium-dioxide particulates and the incidence of lung tumors in dogs reveal beneficial effects when the cumulative alpha-radiation dose is low. There is a threshold at an exposure level of about 100 cGy for excess tumor incidence and reduced lifespan. The observations conform to the expectations of the radiation hormesis dose-response model and contradict the predictions of the LNT hypothesis. These studies suggest investigating the possibility of employing low-dose alpha-radiation, such as from ²³⁹PuO₂ inhalation, as a prophylaxis against lung cancer.