Role of folylpolyglutamate synthetase and folylpolyglutamate hydrolase in methotrexate accumulation and polyglutamylation in childhood leukemia.
Inefficient polyglutamylation is a mechanism of resistance to methotrexate (MTX) in childhood T-lineage acute lymphoblastic leukemia (T-ALL) and in acute myeloid leukemia (AML) in comparison with childhood c/preB-ALL. We analyzed the profile of MTX polyglutamylation in childhood c/preB-ALL, T-ALL, and AML (n = 45, 15, and 14, respectively), the activity of the MTX-polyglutamate synthesizing enzyme folylpolyglutamate synthetase (FPGS) (n = 39, 11, and 19, respectively) and of the MTX-polyglutamate breakdown enzyme folylpolyglutamate hydrolase (FPGH) (n = 98, 25, and 34, respectively). MTX-Glu4-6 accumulation after 24 hours exposure to 1 micromol/L [3H]-MTX in vitro was lower in T-ALL (threefold) and AML (fourfold) compared with c/preB-ALL (P </=.001). The FPGS activity was twofold lower in T-ALL and AML than in c/preB-ALL samples (P <. 01). FPGH activity was not different between c/preB-ALL and T-ALL, but threefold higher in AML (P <.001). FPGS, FPGH, and the ratio FPGS/FPGH were correlated with MTX-Glu4-6 accumulation (r =.49, r = -.34 and r =.61, respectively). Multivariate analysis showed that FPGS, but not FPGH, was an independent contributor for MTX-Glu1-6 accumulation, but not for MTX-Glu4-6 accumulation. In conclusion, low FPGS activity is associated with low accumulation of MTX-Glu4-6 in T-ALL and AML. For the group of AML as compared with the group of ALL, a high FPGH activity can play an additional role.
Departments of Pediatric Hematology/Oncology and of Medical Oncology, University Hospital Vrije Universiteit, Amsterdam, The Netherlands. marianne.rots@azvu.nl
M G
MG
Rots
R
R
Pieters
G J
GJ
Peters
P
P
Noordhuis
C H
CH
van Zantwijk
G J
GJ
Kaspers
K
K
Hählen
U
U
Creutzig
A J
AJ
Veerman
G
G
Jansen
D000964:Antimetabolites, Antineoplastic / Q000378:metabolism* / Q000627:therapeutic use; D002648:Child; D002675:Child, Preschool; D019008:Drug Resistance, Neoplasm; D005260:Female; D018698:Glutamic Acid; D006801:Humans; D007223:Infant; D008297:Male; D008727:Methotrexate / Q000378:metabolism* / Q000627:therapeutic use; D010453:Peptide Synthases / Q000378:metabolism*; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000188:drug therapy* / Q000378:metabolism; D011623:gamma-Glutamyl Hydrolase / Q000378:metabolism*
D000964:Antimetabolites, Antineoplastic; D018698:Glutamic Acid; D011623:gamma-Glutamyl Hydrolase; D010453:Peptide Synthases; C023103:folylpolyglutamate synthetase; D008727:Methotrexate