Radiation response of cultured human carcinoembryonic antigen-producing colon adenocarcinoma cells

Abstract

The authors investigated the radiation response of cultured colon carcinoma cells in order to provide clues for the usual poor results of radiation therapy in the treatment of large bowel malignancies. The survival curve of asynchronous exponentially growing cells was a shouldered-exponential pattern typical of mammalian cells ( D q = 170 rad and D o = 100 rad). Qualitatively similar curves were obtained for cells irradiated in stationary phase of growth. Exponentially growing cells exhibited a significant capacity to recover from a “priming” dose of radiation with considerable restitution of the shoulder region of dose-dependent survival curves. Stationary phase cultures were unable to repair potentially lethal damage. There were moderate cell cycle stage-dependent fluctuations in survival for exponentially growing cells. The most sensitive elements were cells in early S phase and the most radioresistant were cells in late G 1. Our studies indicate that cultured colon carcinoma cells have radiobiological parameters similar to those of other mammalian cells and suggest that the clinically observed radioresistance is not a consequence of intrinsic cellular properties or certain cell kinetics factors.