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Table 4 Correlation of cellular MTX polyglutamate levels with mRNA expression of FPGS and FPGH as well as FPGS activity

From: Methotrexate resistance in relation to treatment outcome in childhood acute lymphoblastic leukemia

  Precursor B cell ALL T cell ALL Total ALL
  MTX-Glu1–6 MTX-Glu4–6 MTX-Glu1–6 MTX-Glu4–6 MTX-Glu1–6 MTX-Glu4–6
FPGS mRNA
R −0.168 −0.082 0.345 0.002 0.264 0.280
P value 0.456 0.724 0.176 0.994 0.104 0.104
 Number of patients 22 21 17 14 39 35
FPGH mRNA
R 0.117 0.195 0.366 0.537 0.101 0.045
P value 0.622 0.424 0.219 0.110 0.576 0.817
 Number of patients 20 19 13 10 33 29
FPGS activity
R 0.429* 0.419* 0.265 0.05 0.522* 0.533*
P value 0.005 0.01 0.431 0.898 <0.001 <0.001
 Number of patients 41 37 11 9 52 46
  1. R and Pvalues were estimated using Spearman’s Rho test; the concentration of MTX polyglutamates (MTX-Glu1–6 and MTX-Glu4–6) is expressed as pmol MTX-Glun/109 cells; mRNA expression of folate enzymes is expressed as ratio normalized to β-actin; FPGS activity is expressed as pmol MTX-Glu2 formed/h/106 cells. The asterisk denotes significant (P < 0.05) associations