Oncogenic Transformation of C3H/10T½ Cells by X-rays, Fast-fission Neutrons, and Cyclotron-produced Neutrons

Summary

Lethality and oncogenic transformation were measured in C3H/10T½ murine fibroblasts exposed to neutrons and X-rays at doses between 0·5 and 11 Gy. Transformation results with X-rays and low-energy, reactor-produced neutrons were used as a baseline to compare and evaluate the results obtained with high-energy, cyclotron-produced neutrons. The radiations were 100-kVp X-rays at 0·49 Gy min⁻¹, reactor fission neutrons at 0·10 to 0·31 Gy min⁻¹ with an 8 to 20 per cent gamma dose component, and cyclotron-produced neutrons at 0·51 Gy min⁻¹ with mean energy 38 MeV and an 8 per cent gamma dose component. The radiobiological effectiveness (r.b.e.) for cell lethality was 2·4 ± 0·2 for fission neutrons and 1·7 ± 0·1 for high-energy neutrons. The maximum proportions of transformants per thousand surviving cells were, respectively, 3·7 ± 0·8, 6·5 ± 0·7, and 2·3 ± 0·6 for X-rays, fission neutrons, and cyclotron-produced neutrons. The maximum observed r.b.e. for transformation induction was 3·8 for fission neutrons and 1·2 for cyclotron neutrons. Thus, high-energy neutrons exhibit a higher r.b.e. for cell killing capacity than for oncogenic transformation in C3H/10T½ cells.

• oncogenic transformation
• neutrons