OBJECTIVETo evaluate the value of the "comet" assay in detecting the radiosensitivity in human tumor cell lines.

METHODSThe radiation-induced primary DNA damage and repair were detected by the comet assay in CNE-1 and 973 cell lines. The tail moment was used as the end point, to quantitate the primary DNA damage and subsequent repair ability. The cell-survival curve was plotted by the classical colony assay, to detect the D(0) value and Dq value. The results from the above two assays were compared.

RESULTS1. With the increment of irradiation doses, under the same experimental condition, the radiation-induced primary DNA damage was more severe in CNE-1 cells than in 973 cells (P < 0.01). From the cell-survival curves, the D(0) value was 1.631 and 1.822 in CNE-1 and CNE-1 973 cells respectively, indicating that CNE-1 cells were more sensitive to irradiation than 973 cells. The radiosensitivity detected by comet assay and by colony assay in the two cell lines tended to be consistent. 2. The half-repair time of 973 and CNE-1 cell line was 33 min and 41 min detected by comet assay, which indicats that the ability of DNA damage and repair in CNE-1 cells was weaker than in 973 cells. The Dq value of the cell survival curve was 2.152 for 973 and 0.626 for CNE-1 cell line detected by the colony assay, which indicates that the sublethal damage repair in 973 cells being much faster than in CNE-1 cells. The repair ability reflected by the results in the two cell lines was consistent.

CONCLUSIONThe radiosensitivities reflected by the results of the primary DNA damage and repair detected by both comet assay and colony assay in CNE-1 and 973 cells are consistent. It suggests that comet assay is a good method for detecting the radiosensitivity of tumor cells.