Cell-killing effect of heavy ions in normal human fibroblasts

Abstract

[Introduction] The mechanism by which heavy ions have greater effects than low-LET radiations is not completely understood. In this study, we investigated the cell-killing effect of heavy ions in normal human fibroblasts.
[Materials & Methods] Normal human diploid fibroblasts immortalized with the hTERT telomerase catalytic subunit gene (BJ-hTERT cells) were used. Confluent cell monolayer was irradiated with ⁶⁰Co γ-rays (LET=0.2 keV/μm), helium (17 keV/μm), carbon (70-212 keV/μm), neon (310 and 430 keV/μm) and argon ions (1320 and 1530 keV/μm). Cell survival was determined with a colony formation assay. The 10% survival dose (D₁₀) was calculated from survival curves and RBE based on the D₁₀ was obtained.
[Results & Discussion] D₁₀ values of γ-rays, helium, carbon, neon and argon ions were 4.3, 2.4, 1.0-1.5, 1.6-2.5 and 5.8-7.0 Gy, respectively. RBE reached the maximum at 70 and 110 keV/μm carbon ions. We will also discuss the DNA fragmentation by heavy-ion irradiation in normal human fibroblasts.