Circumvention of methotrexate resistance in childhood leukemia subtypes by rationally designed antifolates

M G Rots, R Pieters, G J Peters, C H van Zantwijk, R Mauritz, P Noordhuis, J C Willey, K Hählen, U Creutzig, G Janka-Schaub, G J Kaspers, A J Veerman, G Jansen

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Cellular methotrexate (MTX) resistance may cause treatment failure in childhood common/preB-acute lymphoblastic leukemia (c/preB-ALL), T-lineage ALL (T-ALL), and acute myeloid leukemia (AML). The ex vivo potency of several antifolates (MTX, trimetrexate [TMQ], GW1843U89, multitargeted antifolate [MTA], Raltitrexed, and ZD9331) was studied via in situ inhibition of thymidylate synthase (TS). After short-term exposure, relapsed c/preB-ALL (rALL, n = 21), T-ALL (n = 22), and AML (n = 22) were 3-fold, 10-fold, and 6-fold less sensitive to MTX (P </=.01) compared with initial c/preB-ALL (n = 43). This difference in resistance was not observed for TMQ. Also for GW1843U89 and MTA, no resistance was observed in rALL and AML compared with c/preB-ALL. T-ALL compared with c/preB-ALL tended to be less resistant to GW1843U89 (3-fold) and MTA (6-fold) than to MTX (10-fold) (P =.06). Raltitrexed was more active against c/preB-ALL compared with the other subtypes. After 21 hours continuous incubation, T-ALL and AML samples were equally sensitive as c/preB-ALL to MTX, but rALL was 3-fold resistant to MTX compared with initial c/preB-ALL (P =.003). The resistance of rALL was circumvented by TMQ (1-fold; P =.03) and GW1843U89 (1.4-fold; P =. 004). Novel antifolates, except MTA, displayed a more potent TS inhibition than MTX during continuous exposure. These results suggest that MTX resistance in AML and T-ALL can be circumvented by continuous exposure, and that novel antifolates should be explored further for MTX-resistant T-ALL, rALL, and AML cells.

Original languageEnglish
Pages (from-to)3121-8
Number of pages8
Issue number9
Publication statusPublished - 1 Nov 1999

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Rots, M. G., Pieters, R., Peters, G. J., van Zantwijk, C. H., Mauritz, R., Noordhuis, P., ... Jansen, G. (1999). Circumvention of methotrexate resistance in childhood leukemia subtypes by rationally designed antifolates. Blood, 94(9), 3121-8.