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Table 2 MTX resistance-related variables in precursor B and T cell ALL

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

  Precursor B cell ALL T cell ALL
  N Median (range) N Median (range) P value
TSIA cont. 85 0.058 (0.01–0.76) 30 0.062 (0.01–0.22) 0.595
TSIA short 87 0.37 (0.16–12.97) 30 1.44 (0.16–40.0) <0.001
MTX-Glu1–6 97 1210 (120–4838) 31 630 (314–1943) <0.001
MTX-Glu4–6 83 856 (80–3190) 25 260 (0–843) <0.001
DHFR mRNA 37 3.86 (0.27–55.06) 17 12.42 (1.48–34.11) <0.001
TS mRNA 37 2.64 (0.24–23.04) 18 10.26 (1.64–25.04) <0.001
FPGS mRNA 32 6.26 (1.12–39.64) 20 2.39 (0.52–17.20) 0.008
FPGH mRNA 27 2.12 (0.16–18.00) 16 4.83 (0.18–27.65) 0.196
RFC mRNA 35 0.89 (0.24–6.90) 20 0.79 (0.23–4.79) 0.668
FPGS activity 57 1.01 (0.03–11.33) 16 0.18 (0.02–1.57) <0.001
  1. P value is determined by the Mann–Whitney U test; TSIA continuous (TSIA cont.) and short-term exposure (TSIA short) are expressed as the concentration of MTX (in μM) necessary to inhibit 50 % of the TS activity (TSI50) compared to the controls incubated without MTX (in triplicate); the concentration of MTX polyglutamates (MTX-Glu1–6 and MTX-Glu4–6) are 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