DNA polymerases in irradiated regressing or regrowing EMT6 tumor

The EMT6 tumor of Balb/C mice was studied in vivo for irradiation response. It showed a typical, progressive Gompertzian growth mode in control tumors, and, after irradiation with 2000, 4000 or 6000 rad, a regression and regrowth pattern. This solid tumor model was studied with serial DNA-polymerase (DNA-P) alpha and B assays after irradiation-perturbed growth. The DNA-P activity was traced during growth and injury-regrowth to study its behavior as a potential marker for tumor activity. DNA-P alpha level fell after high dose irradiation, remained low during the early regeneration period, and rose again after a regrowth pattern was established. The changes in activity followed DNA-S activity by H3TDR uptake. DNA-P B activity did not change after irradiation.