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Table 3 Correlation of the TSIA assay (continuous and short exposure) with accumulation of MTX polyglutamates and TS mRNA expression

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

 

Precursor B cell ALL

T cell ALL

Total ALL

 

TSIA cont.

TSIA short

TSIA cont.

TSIA short

TSIA cont.

TSIA short

MTX-Glu1–6

 Correlation coefficient

−0.547*

−0.495*

−0.094

−0.128

−0.432*

−0.524*

  P value

<0.001

<0.001

0.685

0.612

<0.001

<0.001

 Number of patients

64

58

21

18

85

76

MTX-Glu4–6

 Correlation coefficient

−0.494*

−0.503*

−0.258

0.046

−0.399*

−0.568*

  P value

<0.001

<0.001

0.336

0.875

0.001

<0.001

 Number of patients

54

50

16

14

70

64

TS mRNA

 Correlation coefficient

0.591

0.678*

0.139

0.483

0.466*

0.693*

  P value

0.056

0.045

0.701

0.187

0.033

0.001

 Number of patients

11

9

10

9

21

18

  1. P value was estimated using Spearman’s Rho 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) is expressed as pmol MTX-Glun/109 cells; TS mRNA level is expressed as ratio normalized to β-actin. The asterisk denotes significant (P < 0.05) associations