Involvement of the ABCB1 C3435T Variant but Not the MTHFR C677T or MTHFR A1298C Variant in High-Dose Methotrexate-Induced Toxicity in Pediatric Acute Lymphoblastic Leukemia Patients in China

Figures & data

Table 1 Patient Main Characteristics and Frequencies of Genetic Polymorphisms

Characteristic	Number of Patients (%)
Gender
Male	57 (53.8)
Female	49 (46.2)
Subtype of tumor
B	96 (90.6)
T	10 (9.4)
Degree of risk
Low-risk	64 (60.4)
Intermediate- and high-risk	42 (39.6)
Age (years)
<1	1 (0.9)
1–9	93 (87.7)
≥10	12 (11.3)
MTHFR
677C > T
CC	18 (17.0)
CT	43 (40.6)
TT	45 (42.4)
T allele	133 (62.7)
1298A > C
AA	84 (79.2)
AC	21 (19.8)
CC	1 (0.9)
C allele	23 (10.8)
ABCB1
3345 C > T
CC	47 (44.3)
CT	49 (46.2)
TT	10 (9.4)
T allele	69 (32.5)

Notes: Data are presented as numbers (%).

Table 2 Number of Courses per Grade of Adverse Events (n=106)

Adverse events	Grade n (%)
	0	1	2	3	4
Leucopenia	30 (28.3)	23 (21.7)	24 (22.6)	27 (25.5)	2 (1.9)
Anemia	9 (8.5)	23 (21.7)	58 (54.7)	16 (15.1)	0 (0)
Neutropenia	53 (50.0)	8 (7.5)	20 (18.9)	22 (20.8)	3 (2.8)
Depressed PLT	97 (91.5)	7 (6.6)	1 (0.9)	0 (0)	1 (0.9)
Elevated ALT	38 (35.8)	43 (40.6)	15 (14.2)	9 (8.5)	1 (0.9)
Elevated AST	41 (38.7)	46 (43.4)	11 (10.4)	8 (7.5)	0 (0)
Vomiting	99 (93.4)	6 (5.7)	1 (0.9)	0 (0)	0 (0)
Oral mucositis	98 (92.5)	6 (5.7)	1 (0.9)	1 (0.9)	0 (0)

Notes: Data are presented as numbers (%).

Abbreviations: PLT, platelet count; ALT, alanine transferase; AST, aspartate transferase.

Table 3 The Correlation Between Genotyping and MTX Elimination Delay

Polymorphism	Genotype	No. of patients (%)	44-hour plasma MTX level (μmol/L)		P value
			≤1 (n = 85, %)	>1 (n = 21, %)
MTHFR 677C > T	CC	18 (17.0)	15 (83.3)	3 (16.7)
	CT	43 (40.6)	34 (79.1)	9 (20.9)	0.897
	TT	45 (42.4)	37 (82.2)	8 (17.8)
MTHFR 1298A > C	AA	84 (79.2)	68 (81.0)	16 (19.0)
	AC	21 (19.8)	17 (81.0)	4 (19.0)	1.000
	CC	1 (0.9)	1 (100.0)	0 (0.0)
ABCB1 3345 C > T	CC	47 (44.3)	38 (80.9)	9 (19.1)
	CT	49 (46.2)	40 (81.6)	9 (18.4)	1.000
	TT	10 (9.4)	8 (80.0)	2 (20.0)

Notes: Data are presented as numbers (%). P<0.05.

Table 4 Analysis of Genotyping and Methotrexate-Induced Toxicity (≥ Grade 1)

Polymorphism	Genotype	Non-Toxicity n (%)	Toxicity n (%)	OR	P	95% CI
MTHFR 677C > T		Leucopenia (< grade 1)	Leucopenia (≥ grade 1)
	CC	8 (44.4)	10 (55.6)	Reference
	CT	25 (58.1)	18 (41.9)	0.576	0.330	0.190–1.747
	TT	20 (44.4)	25 (55.6)	1.000	1.000	0.333–3.004
		Neutropenia (< grade 1)	Neutropenia (≥ grade 1)
	CC	10 (55.6)	8 (44.4)	Reference
	CT	25 (58.1)	18 (41.9)	0.900	0.852	0.297–2.730
	TT	26 (57.8)	19 (42.2)	0.913	0.872	0.303–2.750
		Elevated AST (< grade 1)	Elevated AST (≥ grade 1)
	CC	7 (38.9)	11 (61.1)	Reference
	CT	18 (41.9)	25 (58.1)	0.884	0.830	0.287–2.722
	TT	16 (35.6)	29 (64.4)	1.153	0.804	0.374–3.561
		Vomiting (< grade 1)	Vomiting (≥ grade 1)
	CC	18 (100)	0 (0)	Reference
	CT	40 (93.0)	3 (7.0)	NE	0.998	NE
	TT	41 (91.1)	4 (8.9)	NE	0.998	NE
		Oral mucositis (< grade 1)	Oral mucositis (≥ grade 1)
	CC	18 (100)	0 (0)	Reference
	CT	38 (88.4)	5 (11.6)	NE	0.998	NE
	TT	42 (93.3)	3 (6.7)	NE	0.998	NE
MTHFR 1298A > C		Leucopenia (< grade 1)	Leucopenia (≥ grade 1)
	AA	40 (47.6)	44 (52.4)	Reference
	AC	12 (57.1)	9 (42.9)	0.682	0.436	0.260–1.789
	CC	1 (100)	0 (0)	NE	1.000	NE
		Neutropenia (< grade 1)	Neutropenia (≥ grade 1)
	AA	46 (54.8)	38 (45.2)	Reference
	AC	14 (66.7)	7 (33.3)	0.605	0.327	0.222–1.652
	CC	1 (100)	0 (0)	NE	1.000	NE
		Elevated AST (< grade 1)	Elevated AST (≥ grade 1)
	AA	32 (38.1)	52 (61.9)	Reference
	AC	9 (42.9)	12 (57.1)	0.821	0.689	0.311–2.164
	CC	0 (0)	1 (100)	NE	1.000	NE
		Vomiting (< grade 1)	Vomiting (≥ grade 1)
	AA	77 (91.7)	7 (8.3)	Reference
	AC	21 (100)	0 (0)	NE	0.998	NE
	CC	1 (100)	0 (0)	NE	1.000	NE
		Oral mucositis (< grade 1)	Oral mucositis (≥ grade 1)
	AA	77 (91.7)	7 (8.3)	Reference
	AC	20 (95.2)	1 (4.8)	0.550	0.586	0.064–4.732
	CC	1 (100)	0 (0)	NE	1.000	NE
ABCB1 3345 C > T		Leucopenia (< grade 1)	Leucopenia (≥ grade 1)
	CC	29 (61.7)	18 (38.3)	Reference
	CT	22 (44.9)	27 (55.1)	1.977	0.101	0.876–4.463
	TT	2 (20.0)	8 (80.0)	6.444	0.028*	1.229–33.803
		Neutropenia (< grade 1)	Neutropenia (≥ grade 1)
	CC	32 (68.1)	15 (31.9)	Reference
	CT	26 (53.1)	23 (46.9)	1.887	0.134	0.822–4.333
	TT	3 (30.0)	7 (70.0)	4.978	0.034*	1.127–21.978
		Elevated AST (< grade 1)	Elevated AST (≥ grade 1)
	CC	19 (40.4)	28 (59.6)	Reference
	CT	17 (34.7)	32 (65.3)	1.277	0.562	0.558–2.923
	TT	5 (50.0)	5 (50.0)	0.679	0.579	0.172–2.670
		Vomiting (< grade 1)	Vomiting (≥ grade 1)
	CC	45 (95.7)	2 (4.3)	Reference
	CT	45 (91.8)	4 (8.2)	2.000	0.437	0.349–11.474
	TT	9 (90.0)	1 (10.0)	2.500	0.473	0.204–30.605
		Oral mucositis (< grade 1)	Oral mucositis (≥ grade 1)
	CC	45 (95.7)	2 (4.3)	Reference
	CT	46 (93.9)	3 (6.1)	1.467	0.682	0.234–9.201
	TT	7 (70.0)	3 (30.0)	9.643	0.023*	1.360–68.349

Notes: OR values were computed considering the number of MTHFR 677CC, MTHFR 1298AA or ABCB1 3345CC cases as a reference. *P<0.05.

Abbreviations: AST, aspartate transferase; OR, odds ratio; CI, confidence interval; NE, not estimable.

Table 5 Analysis Among the Number of Wild Homozygous Genes and Methotrexate-Induced Toxicity (≥ Grade 1)

	The Number of Wild Homozygous Genes				P
	0	1	2	3
Leucopenia (≥ grade 1)
Yes, n=76	5	39	29	3	0.551
No, n=30	0	18	11	1
Neutropenia (≥ grade 1)
Yes, n=53	3	30	19	1	0.729
No, n=53	2	27	21	3
Depressed hemoglobin (≥ grade 1)
Yes, n=97	5	55	33	4	0.114
No, n=9	0	2	7	0
Depressed PLT (≥ grade 1)
Yes, n=9	0	3	6	0	0.230
No, n=97	5	54	34	4
Elevated ALT (≥ grade 1)
Yes, n=68	4	35	27	2	0.750
No, n=38	1	22	13	2
Elevated AST (≥ grade 1)
Yes, n=65	3	35	25	2	1.000
No, n=41	2	22	15	2
Vomiting (≥ grade 1)
Yes, n=7	0	5	2	0	0.840
No, n=99	5	25	38	4
Oral mucositis (≥ grade 1)
Yes, n=8	1	5	2	0	0.585
No, n=98	4	52	38	4

Notes: Data are presented as numbers. P<0.05.

Abbreviations: PLT, platelet count; ALT, alanine transferase; AST, aspartate transferase.

Data Sharing Statement

All data generated or analyzed during this study are included in this article. Further inquiries can be directed to the corresponding author.