Comparison of Heat and/or Radiation Sensitivity and Membrane Composition of Seven X-Ray-transformed C3H 1OT¹/₂ Cell Lines and Normal C3H IOTV2 Cells

C3H 10T¹/₂mouse embryo cells were transformed by X-irradiation, and seven transformed clones were isolated and propagated as cell lines. Some of these cell lines produced tumors in syngeneic mice and grew in agarose while the normal C3H IO¹/₂ cell line did not possess these characteristics. Exponentially growing cell cultures with comparable cell-cycle distributions as measured by flow cytometry were tested for heat and X-ray sensitivity. The heat and X-ray sensitivity varied randomly compared to the normal cell line. One cell line was more heat resistant and one more heat sensitive than the normal cell line, and the others had sensitivities comparable to the normal cell line. Measurements on some of the biochemical parameters of the particulate fraction of cells after sonicatton and 24,000 x g centrifugation showed that altered thermal sensitivity was not correlated with protein, cholesterol, or phospholipid content of this fraction.