Radiation effects on lung carcinogenesis in neonatal, juvenile, and adult Wistar rats after thoracic X-ray irradiation. Rattus norvegicus

Studies of radiation exposed populations have shown that children are at greater overall risk of radiation-induced cancer, although there is considerable debate relating to heterogeneity of the effect in different tissues. Given public concern around increasing radiation doses received by children from advanced diagnostic imaging, and the use of radiotherapy to treat childhood cancers, understanding the relationship between age-at-exposure and radiation-induced cancer risk is a priority of radiation protection research. Although tobacco smoking accounts for up to 90% of lung cancers in some countries, epidemiological studies and animal experiments show that exposure to ionizing radiation is also a risk factor for developing cancers of the lung. Female Wistar rats are susceptible to lung cancer upon thoracic X-ray irradiation, developing adenocarcinomas (AC) and squamous cell carcinomas (SCC) similar to those seen in humans, and have been used previously to evaluate the interaction of radiation and a chemical carcinogen in neonatal, juvenile and young adult rats. In the present study, the induction of lung tumors was analyzed in female Wistar rats exposed to increasing doses of thoracic X-rays as neonates, juveniles or adults, to allow the effect of age-at-exposure to be observed in the absence of interaction with smoking. Histology was used to compare tumor subtypes between groups, and genomic DNA copy number alterations in a number of tumors arising after exposure to radiation at different ages were examined. Overall design: The experiment contains three individual rat lung adenocarcinomas from each of four groups (total 12 samples): one group of rats receiving no treatment (spontaneous adenocarcinomas) and three groups receiving X-ray irradiation (1-5 Gy) at either 1 week, 5 weeks or 15 weeks of age. Each tumour is represented by one array, with two arrays per slide, on a total of six array slides. It is not possible to know whether the adenocarcinomas from the irradiated rats are radiation-induced.