Alpha-particles Induce Preneoplastic Transformation of Rat Tracheal Epithelial Cells in Culture

Summary

To characterize the potential role of high-l.e.t. radiation in respiratory carcinogenesis, the cytotoxic and transforming potency of 5·5 MeV α-particles from electroplated sources of ²³⁸Pu were determined using primary cultures of rat tracheal epithelial cells. The α-particle response was compared to the effects of 280 kVp X-rays and of the direct-acting carcinogen N-methyl-N'-nitro-N-nitrosoguanidine. Increasing the α-particle dose caused an exponential decrease in survival with a D₃₇ of 1·6 Gy. X-rays also caused a dose-dependent decrease in survival (D₃₇ = 3·6 Gy) but the survival curve had a significant shoulder. The RBE for cell killing by α-particles versus X-rays varied with dose, and ranged between 4 and 1·5 for α doses in the range 0·2–4 Gy. At equally toxic doses (relative survival 0·18–0·2), all three agents induced similar frequencies of preneoplastic transformation. For preneoplastic transformation induced by doses of α- and X-radiations giving 80 per cent toxicity, an α RBE of 2·4 was derived. The similar RBEs for cell killing and for preneoplastic transformation suggest an association between the type or degree of radiation-induced damage responsible for both cell killing and cell transformation.