Biomaterial Database

Low-dose ionizing radiation decreases the frequency of neoplastic transformation to a level below the spontaneous rate in C3H 10T1/2 cells. 1996

E I Azzam, and S M de Toledo, and G P Raaphorst, and R E Mitchel

Radiation Biology and Health Physics Branch, Atomic Energy of Canada Limited, Chalk River Laboratories, Ontario, Canada.

We have previously shown that chronic exposure of plateau-phase C3H 10 T1/2 cells to (60)Co gamma radiation at doses as low as 10 cGy protected the cells against neoplastic transformation by a subsequent large acute radiation exposure. We have also shown that this induced resistance to neoplastic transformation correlated with an increased ability to repair radiation-induced chromosome breaks. We now show that a single exposure of quiescent cells to doses as low as 0.1 cGy also reduces the risk of neoplastic transformation, from the spontaneous level to a rate three- to fourfold below that level. Higher doses, up to 10 cGy at the same dose rate (0.24 cGy/min), did not reduce the neoplastic transformation frequency further. This protective effect was seen only in irradiated cells that were allowed to incubate at 37 degrees C before release from contact inhibition. Cells released into low-density subcultures immediately after irradiation had unchanged neoplastic transformation frequencies. These results demonstrate that low or chronic exposure to radiation can induce processes which protect the cell against naturally occurring as well as radiation-induced alterations that lead to cell transformation. If similar processes are induced in human cells, the results also suggest that a single low dose, at background or occupational exposure levels, may in some circumstances reduce rather than increase cancer risk, a conclusion inconsistent with the linear no-threshold model of cancer risk from radiation.

UI	MeSH Term	Description	Entries
D007399	Interphase	The interval between two successive CELL DIVISIONS during which the CHROMOSOMES are not individually distinguishable. It is composed of the G phases (G1 PHASE; G0 PHASE; G2 PHASE) and S PHASE (when DNA replication occurs).	Interphases
D009381	Neoplasms, Radiation-Induced	Tumors, cancer or other neoplasms produced by exposure to ionizing or non-ionizing radiation.	Radiation-Induced Cancer,Cancer, Radiation-Induced,Radiation-Induced Neoplasms,Cancer, Radiation Induced,Cancers, Radiation-Induced,Neoplasm, Radiation-Induced,Neoplasms, Radiation Induced,Radiation Induced Cancer,Radiation Induced Neoplasms,Radiation-Induced Cancers,Radiation-Induced Neoplasm
D011836	Radiation Tolerance	The ability of some cells or tissues to survive lethal doses of IONIZING RADIATION. Tolerance depends on the species, cell type, and physical and chemical variables, including RADIATION-PROTECTIVE AGENTS and RADIATION-SENSITIZING AGENTS.	Radiation Sensitivity,Radiosensitivity,Sensitivity, Radiation,Tolerance, Radiation,Radiation Sensitivities,Radiation Tolerances,Radiosensitivities,Sensitivities, Radiation,Tolerances, Radiation
D011853	Radiobiology	Study of the scientific principles, mechanisms, and effects of the interaction of ionizing radiation with living matter. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)	Radiation Biology,Biology, Radiation
D002460	Cell Line	Established cell cultures that have the potential to propagate indefinitely.	Cell Lines,Line, Cell,Lines, Cell
D002471	Cell Transformation, Neoplastic	Cell changes manifested by escape from control mechanisms, increased growth potential, alterations in the cell surface, karyotypic abnormalities, morphological and biochemical deviations from the norm, and other attributes conferring the ability to invade, metastasize, and kill.	Neoplastic Transformation, Cell,Neoplastic Cell Transformation,Transformation, Neoplastic Cell,Tumorigenic Transformation,Cell Neoplastic Transformation,Cell Neoplastic Transformations,Cell Transformations, Neoplastic,Neoplastic Cell Transformations,Neoplastic Transformations, Cell,Transformation, Cell Neoplastic,Transformation, Tumorigenic,Transformations, Cell Neoplastic,Transformations, Neoplastic Cell,Transformations, Tumorigenic,Tumorigenic Transformations
D004307	Dose-Response Relationship, Radiation	The relationship between the dose of administered radiation and the response of the organism or tissue to the radiation.	Dose Response Relationship, Radiation,Dose-Response Relationships, Radiation,Radiation Dose-Response Relationship,Radiation Dose-Response Relationships,Relationship, Radiation Dose-Response,Relationships, Radiation Dose-Response
D005720	Gamma Rays	Penetrating, high-energy electromagnetic radiation emitted from atomic nuclei during NUCLEAR DECAY. The range of wavelengths of emitted radiation is between 0.1 - 100 pm which overlaps the shorter, more energetic hard X-RAYS wavelengths. The distinction between gamma rays and X-rays is based on their radiation source.	Gamma Wave,Gamma Radiation,Nuclear X-Rays,Radiation, Gamma,X-Rays, Nuclear,Gamma Radiations,Gamma Ray,Gamma Waves,Nuclear X Rays,Nuclear X-Ray,Ray, Gamma,Wave, Gamma,Waves, Gamma,X Rays, Nuclear,X-Ray, Nuclear
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia