DNA-DAMAGING EFFECT OF CYCLOPHOSPHAMIDE ON HUMAN BLOOD-CELLS IN-VIVO AND IN-VITRO STUDIED WITH THE SINGLE-CELL GEL TEST (COMET ASSAY)

The single-cell gel (SCG) test was used to study the induction and per sistence of DNA damage by cyclophosphamide (CP) in human blood cells a fter treatment in vitro and in vivo. S9-mix-activated CP (from 0.1 mM upward) induced DNA effects in a concentration-dependent manner in the in-vitro SCG test. Blood cells from various donors showed considerabl e intra- and interindividual variability. Incubation of CP-treated blo od samples at 37 degrees C caused a rapid decrease in DNA effects, but DNA migration was still significantly increased 1 hr after the end of the CP treatment. Comparative studies with the in vitro sister chroma tid exchange (SCE) test were performed that demonstrated that much low er CP concentrations (about 100 times) were required for a significant induction of SCEs. A group of 11 patients who suffered from vasculiti s/collagen disease and were treated with low CP doses (50-200 mg/day) exhibited an elevated level of DNA damage in the SCG test with periphe ral blood cells, compared with a group of 11 control persons or 5 pati ents without chemotherapy. Increases in DNA damage were variable and n ot clearly related to the CP dose. SCE tests could successfully be per formed with 5 out of the 11 CP-treated patients; all showed significan tly increased SCE frequencies. For six patients no result could be obt ained with the SCE test due to a failure of lymphocyte proliferation. Three multiple sclerosis patients who received high doses of CP were i nvestigated with the SCG test before, during, and after the treatment. The results indicate that CP-induced DNA effects that are detectable with the SCG test persist in vivo for a period of several days, but fo r less than 2 weeks. The results of our study provide information with regard to the use of the SCG test in human monitoring. The advantages and limitations of the test ore discussed. (C) 1995 Wiley-Liss, Inc.