Survival of Human Normal Thyroid Cells after X-ray Irradiation

Hiraoka, Takeo; Miller, Richard C.; Gould, Michael N.; Kopecky, Kenneth J.; Ezaki, Haruo; Takeichi, Nobuo; Ito, Toshio; Jones, Michael P.; Clifton, Kelly H.

doi:10.1080/09553008514550441

Cited by 12 publications

(2 citation statements)

References 22 publications

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“…Although the number of clonogens in human thyroid is still to be determined, the thyroid epithelial cells derived from surgically removed thyroid tissues have been cultured in vitro, and radiation sensitivity has been determined by colony-forming assay. The mean D 0 dose was estimated to be 0.93–0.94 Gy (Hiraoka et al., 1985; Miller et al., 1987).…”

Section: Annex a Haematopoietic Tissues: Role Played By Stem Cells Amentioning

confidence: 99%

ICRP Publication 131: Stem Cell Biology with Respect to Carcinogenesis Aspects of Radiological Protection

et al. 2015

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This report provides a review of stem cells/progenitor cells and their responses to ionising radiation in relation to issues relevant to stochastic effects of radiation that form a major part of the International Commission on Radiological Protection's system of radiological protection. Current information on stem cell characteristics, maintenance and renewal, evolution with age, location in stem cell 'niches', and radiosensitivity to acute and protracted exposures is presented in a series of substantial reviews as annexes concerning haematopoietic tissue, mammary gland, thyroid, digestive tract, lung, skin, and bone. This foundation of knowledge of stem cells is used in the main text of the report to provide a biological insight into issues such as the linear-no-threshold (LNT) model, cancer risk among tissues, dose-rate effects, and changes in the risk of radiation carcinogenesis by age at exposure and attained age. Knowledge of the biology and associated radiation biology of stem cells and progenitor cells is more developed in tissues that renew fairly rapidly, such as haematopoietic tissue, intestinal mucosa, and epidermis, although all the tissues considered here possess stem cell populations. Important features of stem cell maintenance, renewal, and response are the microenvironmental signals operating in the niche residence, for which a well-defined spatial location has been identified in some tissues. The identity of the target cell for carcinogenesis continues to point to the more primitive stem cell population that is mostly quiescent, and hence able to accumulate the protracted sequence of mutations necessary to result in malignancy. In addition, there is some potential for daughter progenitor cells to be target cells in particular cases, such as in haematopoietic tissue and in skin. Several biological processes could contribute to protecting stem cells from mutation accumulation: (a) accurate DNA repair; (b) rapidly induced death of injured stem cells; (c) retention of the DNA parental template strand during divisions in some tissue systems, so that mutations are passed to the daughter differentiating cells and not retained in the parental cell; and (d) stem cell competition, whereby undamaged stem cells outcompete damaged stem cells for residence in the niche. DNA repair mainly occurs within a few days of irradiation, while stem cell competition requires weeks or many months depending on the tissue type. The aforementioned processes may contribute to the differences in carcinogenic radiation risk values between tissues, and may help to explain why a rapidly replicating tissue such as small intestine is less prone to such risk. The processes also provide a mechanistic insight relevant to the LNT model, and the relative and absolute risk models. The radiobiological knowledge also provides a scientific insight into discussions of the dose and dose-rate effectiveness factor currently used in radiological protection guidelines. In addition, the biological information contributes potential reasons for the ...

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Section: Annex a Haematopoietic Tissues: Role Played By Stem Cells Amentioning

confidence: 99%

ICRP Publication 131: Stem Cell Biology with Respect to Carcinogenesis Aspects of Radiological Protection

et al. 2015

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“…Accordingly, a study on the amount of radiation exposure from each dental diagnostic X-ray type is needed. Nonetheless, the selected papers on thyroid cancer, which has a high level of radiation sensitivity [42], did not categorize dental diagnostic X-ray types, so this could not be examined.…”

Section: Discussionmentioning

confidence: 99%

Health effects from exposure to dental diagnostic X-ray

Hwang

Choi

Kim

et al. 2018

Environ Health Toxicol

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The purpose of this review is to summarize the results of studies on of the association between exposure to dental X-rays and health risk. To perform the systematic review, We searched the PUBMED, EMBASE, and MEDLINE databases for papers published before December 15, 2016. A total of 2 158 studies, excluding duplicate studies, were found. Two reviewers independently evaluated the eligibility of each study. The final 21 studies were selected after application of exclusion criteria. In terms of health outcomes, there were 10 studies about brain tumors, 5 about thyroid cancer, 3 about tumors of head and neck areas, and 3 related to systemic health. In brain tumor studies, the association between dental X-ray exposure and meningioma was statistically significant in 5 of the 7 studies. In 4 of the 5 thyroid-related studies, there was a significant correlation with dental diagnostic X-rays. In studies on head and neck areas, tumors included laryngeal, parotid gland, and salivary gland cancers. There was also a statistically significant correlation between full-mouth X-rays and salivary gland cancer, but not parotid gland cancer. Health outcomes such as leukemia, low birth weight, cataracts, and thumb carcinomas were also reported. In a few studies examining health effects related to dental X-ray exposure, possibly increased risks of meningioma and thyroid cancer were suggested. More studies with a large population and prospective design are needed to elaborate these associations further.

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