Heterogeneity in the Radiation Survival Curves and Biochemical Properties of Human Lung Cancer Cell Lines

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Abstract
Human lung cancers of distinct histology exhibit different responses to radiation therapy in vivo. For examination of the basis of this phenomenon, the radiation survival curves and levels of relevant enzymes were determined in 16 lung cancer cell lines derived from tumors of different histology. These included lines from 5 adenocarcinomas, 7 small cell tumors, 3 variant small cell tumors, and 1 large cell tumor. These findings were compared to those obtained with the use of a normal skin fibroblast cell line. Whether cloned in liquid culture or soft agarose, cell lines had similar radiation survival curves. These curves were consistent with the apparent in vivo radiation responsiveness of the tumors. Although considerable heterogeneity in radiation survival curves was observed among the cell lines, cells from large cell lines and small variant lines had pronounced shoulders and extrapolation numbers (n) from 5.6 to 14. In contrast, cells from small cell lines and adenocarcinoma cell lines were more “sensitive” (n̅ values of 1–3.3). In these cell lines, levels of DNA polymerase β, glutathione (GSH), GSH transferase, GSH reductase (NAD(P)H), γ-glutamyltransferase did not correlate with radiation parameters of sensitivity. DNA polymerase (β and GSH levels were, however, higher than those in a line of normal skin fibroblasts. These cell lines may be useful in identifying the basis of the variable responsiveness of human lung cancer cells to ionizing radiation.