Malignant transformation of human fibroblasts by neutrons and by gamma radiation: Relationship to mutations induced

The overall objective of this study is to determine whether there is an inverse dose rate effect for cell transformation of human cells treated with ionizing radiation and/or neutron radiation. The initial finding of an inverse dose effect on transformation of C3H/10T 1/2 cells by neutron radiation by Elkind and his colleagues was treated with skepticism, but studies with C3H/10T 1/2 cells by Hall and colleagues, as well as others, have verified the finding. However, not all studies have found such an effect when using C3H/10T 1/2 cells. A further problem is that the C3H/10T 1/2 cell line itself gives a very high induced transformation up to 3%. This would appear not to be compatible with a genetic change. Yet, the current theory regarding carcinogenesis supported by almost all recent studies is that a cancer cell results from the ''activation'' of appropriate proto-oncogenes and/or the inactivation of appropriate suppressor genes within a single cell, i.e., genetic changes. Thus, the possibility exists that the inverse dose effect phenomeria is peculiar to C3H/10T 1/2 cells. This possibility must be seriously considered since the C3H/10T 1/2 transformation assay has been in existence for 20 years, but the mechanism by which the cells become transformed have not yet been successfully elucidated