Response of cultured human airway epithelial cells to X-rays and energetic alpha-particles

Radon and its progeny, which emit alpha-particles during decay, may play an important role in inducing human lung cancer. To gain a better understanding of the biological effects of alpha-particles in human lung we studied the response of cultured human airway epithelial cells to X-rays and monoenergetic helium ions. Our experimental results indicated that the radiation response of primary cultures was similar to that for airway epithelial cells that were transformed with a plasmid containing an origin-defective SV40 virus. The RBE for cell inactivation determined by the ratio of D0 for X-rays to that for 8 MeV helium ions was 1.8-2.2. The cross-section for helium ions, calculated from the D0 value, was about 24 microm 2 for cells of the primary culture. This cross-section is significantly smaller than the average geometric nuclear area (approximately 180 microms 2), suggesting that an average of 7.5 alpha-particles (8 MeV helium ions) per cell nucleus are needed to induce a lethal lesion.