THE EFFECT OF 2 TOPOISOMERASE INHIBITORS ON LOW-DOSE HYPERSENSITIVITYAND INCREASED RADIORESISTANCE IN CHINESE-HAMSTER V79 CELLS

A preliminary investigation of the effect of topoisomerase inhibitors on the structure of the survival curve at low doses has been carried o ut in Chinese hamster V79 cells, where there is a deviation from the p redicted response to radiation (Marples and Joiner, Radiat. Res. 113, 41-51, 1993). Cells were treated with one representative drug for each enzyme (topoisomerase I or II) prior to X irradiation in air and asse ssed for cell survival using automated microscopic location of cells. VP-16 causes little or no effect, while camptothecin has a measurable effect up to 2 Gy. The results are discussed in terms of the role of D NA damage and cell cycle in increased radioresistance, which encourage further investigation of the effects of this class of drugs at low do ses.