Characterization of radiation sensitivity of human squamous carcinoma A431 cells

Studies were made of radiosensitivity of human squamous carcinoma cells. Radiobiological studies of various cultures showed fed-plateau phase cells were more sensitive (Dsub(0) 1.3 Gy) than exponentially growing cells (Dsub(0) = 1.5 Gy). After a single dose of 12Gy or two doses of 6Gy irradiation, A431 cultures exhibited a large capacity for potentially lethal damage (PLD) repair, but relatively small sublethal damage (SLD) repair. Flow cytometric analysis with acridine orange (AO) staining demonstrated that there was a shift of the RNA histograms in fed-plateau and spheroid cultures towards lower values, suggesting the presence of a subpopulation of quiescent-cells. Coulter cell volume distributions and flow cytometric analysis showed Q-cells had a small cell volume (approx. 1380 μm3), low RNA content and a G1-like DNA content. Continuous labelling experiments with tritiated thymidine confirmed the non-proliferating nature of Q-cells. Irradiation of Q-cells after isolation from spheroids with between 0 to 10 Gy showed they were more radiosensitive (decreased Dsub(0)) than proliferating-cells isolated, the latter having similar radiosensitivity to exponential G1 cells. (author)