Analyses of differential sensitivities of synchronized HeLa S3 cells to radiations and chemical carcinogens during the cell cycle. III. 4-Nitroquinoline 1-oxide and its derivatives.

Sensitivity to the chemical carcinogens 4-nitroquinoline 1-oxide (4-NQO) and 4-hydroxyaminoquinoline I-oxide (4-HAQO), during the cell cycle of synchronized HeLa S3 cells, decreases from the late S to the early G2 phases. Cells in other phases are relatively sensitive to both carcinogens. [3-H]4-NQO and [ 3-H]4-HAQO seem to be bound preferably more with cellular DNA of the mitotic phase to the middle of the S phase than with that of the late S phase in which the cells are rather insensitive to these carcinogens. However, we found no significant difference in the excision rates of these carcinogens from the DNA of HeLa S3 cells through the cell cycle. These findings indicate that the cyclic variation of 4-NQO and 4-HAQO cell survivals during the cell cycle may be due to the differences in the amounts of 4-NQO and 4-HAQO bound with cellular DNA.