Childhood acute lymphoblastic leukemia (ALL): sister chromatid exchange (SCE) frequency and lymphocyte subpopulations during therapy.

Sister chromatid exchanges (SCE) and lymphocyte subsets of children with acute lymphoblastic leukemia (ALL) were investigated during chemotherapy. The treatment followed protocol ALL-BFM-90. Children with ALL at the time of diagnosis showed statistically significant higher SCE frequencies (4.9 +/- 0.77) than healthy controls (3.6 +/- 0.93; P = 0.002). The in vivo effects of cyclophosphamide (CP) resulted in a dramatic increase of the SCE frequency (20.5 +/- 3.76). This increased SCE level of lymphocytes might reflect an instability of DNA or a deficiency of DNA repair. One could suggest that lymphocytes of children with ALL might have a higher susceptibility to harmful influences; and this could be a co-factor towards the development of the malignant disease. However, immediately 1 week after the administration of CP, the SCE rate decreased. This decline of SCE frequency correlated with a severe reduction of the absolute number of T lymphocytes. The observed reduction of SCE frequency may be due to a loss of T lymphocytes, or SCE became repaired during 1 week.