Changes in the relative proportion of transformation-sensitive polypeptides in giant HeLa cells produced by irradiation with lethal doses of x-rays.

Irradiation of HeLa cells with 1,100 rads (1 rad = 0.01 J/kg = 0.01 Gy) of x-rays yielded a pure population of giant cells 5-7 days after irradiation. These cells do not divide but go through an intermittent DNA synthetic phase. The population of giant cells in S phase (8%) is considerably lower than that of control asynchronous HeLa cells (30%), but 80% of the giant cells go through S phase as determined by 48-hr labeling with [3H]thymidine. Previous studies with high-resolution two-dimensional gel electrophoresis identified 58 [35S]methionine-labeled polypeptides common to human epithelial amnion cells and lung fibroblasts, whose rate of synthesis is sensitive to neoplastic transformation [Bravo, R. & Celis, J. (1982) Clin. Chem. (Winston-Salem, NC) 28, 949-955]. These polypeptides also have been identified in HeLa cells and other transformed human cells such as Detroit 98, Chang liver, Fl-amnion, and WISH-amnion [Bravo, R. & Celis, J. (1982) Clin. Chem. (Winston-Salem, NC) 28, 949-955]. After irradiation of HeLa cells and giant cell formation, the relative proportions of most of the transformation-sensitive polypeptides (43 of 47) reverted to levels similar to those observed in non-tumorigenic cells. This suggests that their relative proportions are dependent on the growth properties of the cells. In particular, the relative proportions of three polypeptides (designated 12g and 60d1 in isoelectric focusing and 27b in nonequilibrium pH gradient electrophoresis) were not affected, indicating that their reduced amounts in transformed cells could reflect a fundamental change that develops during transformation.