Lung cancer response following inhaled radon in the A/J and C57BL/6J mouse

A/J and C57BL/6J mice, strains which differ in susceptibility to chemical-induced lung tumours, were examined for differential sensitivity to radon-induced lung cancer. Sixty weeks after exposure to 952 WLM radon (3.34 J h1 m-3), no lung tumours were found in the control, sham- (one dust-) exposed, or radon-exposed C57BL/6J mice. In contrast, each of the A/J groups had a substantial number of tumours. Although there were no differences in overall lung tumour incidence or multiplicity associated with radon and ore dust exposure in A/J mice, distinct differences in tumour size and histopathological appearance were noted. The ratio of lung adenoma-to-carcinoma found in control A/J mice was 10:1, whereas the ratio in one dust-exposed animals was 10:8 and that in radon-exposed animals was 8:6. Based on these data, particulates appear to modify the promotion-progression of lung cancer in this strain. In addition, the appearance of two very large carcinomas histologically resembling Clara-cell-derived tumours only in the radon-exposed A/J mice and the possibility of alpha-particle-induced killing of target cells in the radon-exposed animals suggests that A/J but not the C57BL/6J, mice may have genes that modify susceptibility to radon-induced lung cancer.