DIHYDROFOLATE-REDUCTASE AND THYMIDYLATE-SYNTHASE IN CHILDHOOD ACUTE LYMPHOBLASTIC-LEUKEMIA

The expression of thymidylate-synthase (TS) and dihydrofolate-reductas e (DHFR) was analysed immunohistochemically in 110 initial and 28 rela psed childhood acute lymphoblastic leukemia (ALL). Relapse-rates were not significantly higher in initial ALL with of overexpression of TS- and DHFR than in ALL without overexpression of the proteins. In additi on, the disease-free survival was not different for patients with TS o r DHFR-negative and TS- or DHFR-positive ALL. No differences were foun d in the overall survival times of patients with relapsed ALL and with or without expression of TS or DHFR. Of the initial ALL 42% showed TS -overexpression, whereas of the relapsed Af,L 64% of the cases were TS -positive (p = 0.03). The corresponding values for DHFR were 20% and 3 2% (p = 0.18). The results demonstrate clearly that expression of the proteins TS and DHFR has no importance for the resistance of Ail altho ugh the proteins increase during treatment.