Mognato, M., Bortoletto, E., Ferraro, P., Baggio, L., Cherubini, R., Canova, S., Russo, A. and Celotti, L. Genetic Damage Induced by In Vitro Irradiation of Human G₀ Lymphocytes with Low-Energy Protons (28 keV/μm): HPRT Mutations and Chromosome Aberrations. Radiat. Res. 160, 52–60 (2003).

Cell survival, mutations and chromosomal effects were studied in primary human lymphocytes exposed in G₀ phase to a proton beam with an incident energy of 0.88 MeV (incident LET of 28 keV/μm) in the dose range 0.125–2 Gy. The curves for survival and mutations at the hypoxanthine-guanine phosphoribosyl transferase locus were obtained by fitting the experimental data to linear and linear-quadratic equations, respectively. In the dose interval 0–1.5 Gy, the α parameters of the curves were 0.42/Gy and 3.6 × 10⁻⁶ mutants/Gy, respectively. The mutation types at the HPRT locus were analyzed by multiplex-PCR in 94 irradiated and 41 nonirradiated clones derived from T lymphocytes from five healthy donors. All clones showed a normal multiplex-PCR pattern and were classified as point mutations. Chromosome aberration data were fitted as a linear function of dose (α = 0.62 aberrations per cell Gy⁻¹). By irradiating G₀ lymphocytes from a single subject with 28 keV/μm protons and γ rays, an RBE of 6.07 was obtained for chromosome aberrations. An overinvolvement of chromosome 9 relative to chromosome 7 was found in chromosome breaks after chromosome painting analysis.