NEURO-ONCOLOGY
The methylenetetrahydrofolate reductase
(MTHFR) variant c.677C.T (A222V)
influences overall survival of patients with
glioblastoma multiforme
University Hospital Bonn, Department of Neurology, Bonn, Germany (M.L., A.S., S.M.); VU University
Hospital Amsterdam, Department of Internal Medicine and Metabolic Unit, Amsterdam, The Netherlands
(Y.S., H.B.); University Hospital Bonn, Department of Neurosurgery, Bonn, Germany (M.S.)
Glioblastoma multiforme (GBM) is the most frequent
primary brain tumor in adults. Prognosis is poor. Using
a series of 214 GBM patients, we observed an effect of
the variant 5,10-methylenetetrahydrofolate reductase
(MTHFR) c.677C.T on overall survival. This effect
was strongest in patients younger than 60 years at diagnosis (overall survival, median 6 SE: genotype CC, 13
6 1 months; CT, 11 6 2 months; TT, 7 6 3 months;
multivariate Cox regression analysis, Wald 5 8.58, p 5
0.007). In addition, the MTHFR genotype significantly
influenced the overall survival of patients with a postoperative Karnofsky score .70 (CC, 12 6 2 months;
CT, 11 6 1 months; TT, 10 6 4 months; Wald 5 5.89,
p 5 0.015). These data suggest the MTHFR c.677C.T
variant is a risk factor for survival in GBM patients.
Neuro-Oncology 10, 548–552, 2008 (Posted to NeuroOncology [serial online], Doc. D07-00129, May 22,
2008. URL http://neuro-oncology.dukejournals.org;
DOI: 10.1215/15228517-2008-020)
Keywords: glioblastoma, glioma, homocysteine,
MTHFR, survival
Received July 12, 2007; accepted October 24, 2007.
Address correspondence to Michael Linnebank, University Hospital
Zurich, Department of Neurology, Frauenklinikstrasse 26, CH-8091
Zurich, Switzerland (michael.linnebank@usz.ch).
Copyright 2008 by the
548Neuro-Oncology
■JSociety
U LY 2 0 0for
6 Neuro-Oncology
M
ethionine metabolism plays an essential role
in DNA methylation (Fig. 1). The enzyme
5-methyltetrahydrofolate-homocysteine
S-methyltransferase (MTR) catalyzes the remethylation of homocysteine to methionine. The latter is activated by ATP to S-adenosylmethionine (SAM), which
provides the methyl groups used for DNA methylation.
MTR depends on cobalamin (vitamin B12) and 5-methyltetrahydrofolate as cofactors. The most important
transporter protein of cobalamin is transcobalamin 2
(Tc2), and 5-methyltetrahydrofolate is synthesized out of
5,10-methylenetetrahydrofolate by 5,10-methylenetetrahydrofolate reductase (MTHFR). Because 5,10-methylenetetrahydrofolate is also directed to the synthesis
of purines and thymidine, MTHFR activity regulates
whether a one-carbon unit of tetrahydrofolate is utilized
for methionine synthesis or for nucleic acid synthesis and
thus for DNA synthesis, stability, and repair.1
Instability of genomic DNA and impaired DNA
methylation are important for the development and progression of many tumors.2 Therefore, functional genetic
variants of methionine metabolism are attractive candidate factors influencing the development and clinical
course of human cancers. Indeed, the MTHFR missense
variant c.677C .T (A222V) and the MTR missense
variant c.2756A.G (D919G) have been correlated with
the incidence of various malignancies. 3 Furthermore,
functional synergisms have been suggested for the variants MTR c.2756A .G and Tc2 c.776C.G (P259R).4
Downloaded from http://neuro-oncology.oxfordjournals.org/ by guest on October 13, 2015
Michael Linnebank, Alexander Semmler, Susanna Moskau, Yvo Smulders, Henk Blom,
and Matthias Simon
Linnebank et al.: MTHFR variant and GBM survival
However, only a few studies have investigated the role
of the genetic variants of methionine metabolism as a
prognostic factor in patients with cancer. In the present
study, we analyzed the effects of four functional polymorphisms of methionine metabolism on the clinical
course of 214 patients with glioblastoma multiforme
(GBM). Although our previous results did not identify
the MTHFR c.677C.T variant as a risk factor for the
incidence of GBM,3 the present study suggests an influence of MTHFR c.677C.T on survival.
Materials and Methods
Patients
This study was approved by the Ethics Committee of the
Medical Faculty of the University of Bonn.
We analyzed 214 GBM patients (41% female; median
age at diagnosis, 62 years; range, 23–80 years; age at
diagnosis, 58 6 12 years, mean 6 SD) who underwent
surgery in the Department of Neurosurgery of the University Hospital Bonn (Bonn, Germany) between 1994
and 2003. All histopathological diagnoses were made
at the Department of Neuropathology/German Brain
Tumor Reference Center at the University of Bonn using
the WHO criteria. 5 A gliosarcoma was diagnosed in
6% of the patients and a giant cell GBM in 3%. Surgical treatment consisted of total resection in 52% of the
patients, subtotal/partial resection in 43%, and biopsy in
5%. Eighty-two percent of patients underwent standard
fractionated postoperative radiotherapy, and 11% underwent additional adjuvant chemotherapy. Thus, adjuvant
therapy after surgery was categorized as none (surgery
only), radiotherapy, and radiation and chemotherapy.
For 107 patients, treatment at tumor relapse could not
be ascertained. Hence, therapy for recurrent tumors was
not included in the statistical analysis. Median overall
survival of all patients (6 SD) was 10 6 1 months (95%
confidence interval, 9–11 months), with 7% censored.
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Fig. 1. Human methionine metabolism. Methionine becomes activated to S-adenosylmethionine (SAM) via methionine adenosyltransferase
(MAT). SAM is a ubiquitous methyl group donor, for example, for the synthesis of biogenic amines and DNA methylation. The degradation
product of SAM is S-adenosylhomocysteine (SAH), which is hydrolyzed to homocysteine via homocysteine hydrolase (SAHH). Homocysteine can be transsulfurated to cystathionine and cysteine via vitamin B6–dependent cystathionine beta-synthase (CBS) and cystathionine gamma-lyase (CGL); alternatively, homocysteine can be remethylated to methionine via 5-methyltetrahydrofolate-homocysteine
S-methyltransferase (MTR; also called methionine synthase), which needs a derivate of vitamin B12 (methylcobalamin) and a derivate of
folate (5-methyltetrahydrofolate; 5-CH3-FH4) as cofactors. Vitamin B12 is transported by transcobalamin 2 (Tc2), and 5-CH3-FH4 is synthesized by flavin adenine dinucleotide (FAD)–dependent 5,10-methylenetetrahydrofolate reductase (MTHFR) from 5,10-methylenetetrahydrofolate (5,10-CH2-FH4), which is synthesized from folate by dihydrofolate reductase (DHFR) in two subsequent steps.
Linnebank et al.: MTHFR variant and GBM survival
Genotyping
The genotypes of four missense variants involved in
methionine metabolism, MTHFR c.677C.T, MTHFR
c.1298A .C, MTR c.2756A .G, and Tc2 c.776C .G,
were determined by PCR amplification of genomic DNA
prepared from peripheral leukocytes with subsequent
restriction analysis as published previously.4
Statistical Analysis
Results
Log rank testing demonstrated a significant influence
of the MTHFR c.677C.T variant, but not of the other
three genetic polymorphisms, on overall survival: CC,
10 6 1 months; CT, 10 6 1 months; TT, 7 6 3 months
(log rank 5 9.21, p 5 0.010; Table 1).
Multivariate Cox regression including the MTHFR
c.677C.T genotype and the clinical data indicated that
important prognostic factors were younger age (linear
variable; Wald 5 7.10, p 5 0.008), higher Karnofsky
score after surgery (linear variable; Wald 5 21.2, p ,
0.001), and adjuvant therapy (none, 2 6 0.35 months;
radiotherapy, 10 6 0.36 months; radiation and chemotherapy, 11 6 0.82 months; Wald 5 7.81, p 5 0.005).
The extent of resection had a statistically significant
influence on survival in the univariate log rank test (total
resection, 10 6 0.69 months; subtotal/partial resection,
8 6 0.85 months; biopsy, 2 6 1.58 months; log rank 5
10.3, p 5 0.006) but not in the multivariate Cox regres-
Discussion
Overall prognosis for GBM patients is grim, with a
median survival of only 12–16 months even in selected
series. However, certain subsets of patients (young age
at diagnosis, high extent of resection, high Karnofsky
score after surgery) can expect to survive for more than
2 years.7 Small therapeutic advances will more likely
translate into a clinically relevant survival benefit in
patients with a relatively good prognosis. Hence, the
identification of prognostic survival factors may allow
more selective treatment, that is, spare those with an
adverse prognosis a toxic therapy, and allow for aggressive treatment in cases for which a meaningful prolongation of survival can be achieved.
Table 1. Kaplan-Meier analysis of the effect of genotype on overall survival: all patients
Variant
Median Overall Survival (6 SE, months)
CC: 10 6 1
AA: 10 6 1
AA: 10 6 1
CC: 8 6 2
MTHFR c.677C.T
MTHFR c.1298A.C
MTR c.2756A.G
Tc2 c.776C.G
CT: 10 6 1
AC: 9 6 1
AG: 9 6 1
CG: 10 6 1
TT: 7 6 3
CC: 14 6 4
GG: 8 6 5
GG: 9 6 2
Log Rank (2 degrees of freedom)
9.21, p 5 0.010
0.60, p 5 0.742
0.07, p 5 0.967
1.52, p 5 0.469
Abbreviations: MTHFR, 5,10-methylenetetrahydrofolate reductase; MTR, 5-methyltetrahydrofolate-homocysteine S-methyltransferase; Tc2,
transcobalamin 2. Owing to multiple testing, the threshold was defined with a 5 0.0125. Censored for MTHFR c.677C.T: CC, n 5 9; CT, n 5 6;
TT, n 5 0.
550
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The log rank test and Kaplan-Meier curves were used
to analyze the effect of the four variants on overall survival. Owing to multiple testing, a was set to 0.0125.
The effect of the MTHFR variant c.677C.T on overall
survival was further investigated by Cox regression, with
simultaneous analysis of MTHFR genotype, age, sex,
postoperative Karnofsky score, extent of resection, and
adjuvant therapy as covariables. In additional explorative
analyses (univariate log rank tests and multivariate Cox
regression analysis with the covariables listed above), the
effect of the MTHFR c.677C.T variant was analyzed
in subgroups of patients defined by adjuvant therapy,
age (,60 years vs. .60 years, the mean and median age
at diagnosis in our population and prior studies6), and
postoperative Karnofsky score (,70 vs. >70). Data are
reported as median 6 SE.
sion analysis (Wald 5 0.68, p 5 0.447). In the multivariate analysis, the effect of the MTHFR c.677C.T genotype on survival was not statistically significant (Wald
5 1.01, p 5 0.316).
Univariate log rank subgroup analysis revealed a
highly significant association of the MTHFR c.677C.T
polymorphism with survival for patients younger than
60 years at diagnosis (37% of our study sample): CC,
13 6 1 months; CT, 11 6 2 months; TT, 7 6 3 months
(log rank 5 9.94, p 5 0.007; Table 2). Multivariate Cox
regression analysis showed that these data were robust;
that is, the effect of the MTHFR c.677C.T variant on
survival in this patient subset was as strong as the effects
of some of the clinical covariables investigated simultaneously: MTHFR c.677C.T (Wald 5 8.58, p 5 0.003),
extent of resection (Wald 5 2.10, p 5 0.148), Karnofsky
score after surgery (Wald 5 12.3, p , 0.001), and adjuvant therapy (Wald 5 3.32, p 5 0.086). No significant
effect was seen for the MTHFR c.677C.T polymorphism for patients .60 years of age (Wald 5 0.27, p 5
0.601).
Additionally, the MTHFR c.677C .T variant was
found to significantly correlate with survival in the
multivariate analysis among patients with a postoperative Karnofsky score .70 regardless of age (CC, 12 6 2
months; CT, 11 6 1 months; TT, 10 6 4 months; Wald
5 5.89, p 5 0.015). No such effect was seen for patients
with a postoperative Karnofsky score ,70 (CC, 5 6 1
months; CT, 4 6 2 months; TT, 5 6 3 months; Wald
5 0.01, p 5 0.951). The MTHFR c.677C.T polymorphism showed no significant correlation with survival in
any of the subgroups defined by adjuvant therapy.
Linnebank et al.: MTHFR variant and GBM survival
Table 2. Influence of MTHFR c.677C.T genotype on median overall survival: univariate (log rank) and multivariate analyses
Median Overall Survival (6SE, months)
Patient Group
CC
CT
All
Age ,60 years
Age .60 years
KPI .70
KPI ,70
10 6 1
13 6 1
968
12 6 2
561
10 6 1
11 6 2
866
11 6 1
462
TT
763
763
665
10 6 4
563
Log Rank
Cox Regression (Wald)
9.21, p 5 0.010
9.94, p 5 0.007
2.56, p 5 0.278
5.23, p 5 0.051
0.42, p 5 0.896
1.01, p 5 0.316
8.58, p 5 0.003
0.27, p 5 0.601
5.89, p 5 0.015
0.01, p 5 0.951
Abbreviation: MTHFR, 5,10-methylenetetrahydrofolate reductase. Covariables included age (except in the subgroups defined by age), sex, postoperative KPI (except
in the subgroups defined by KPI), extent of resection, and adjuvant therapy.
ated with global hypomethylation of genomic DNA.13
Hypomethylation of the O 6 -methylguanine DNA methyltransferase (MGMT) promoter in GBM tumor cells has
been associated with shorter survival in GBM patients
receiving radiotherapy and treated with temozolomide,14
and a correlation between the T-allele of the MTHFR
c.677C.T variant and a decreased MGMT promoter
hypermethylation has already been observed in a series
of uterine cervical cancers.15 Thus, it is tempting to speculate that differential (tumor) DNA methylation due to
MTHFR c.677C.T might constitute the molecular basis
of the association between the MTHFR c.677C.T polymorphism and survival of GBM patients. Accordingly,
Cadieux et al.16 recently demonstrated that the MTHFR
c.677C .T variant or a deletion encompassing the
MTHFR gene locus on chromosome 1p36.3 was associated with global DNA hypomethylation in GBM tissue.
Tumors with DNA hypomethylation or a MTHFR gene
deletion exhibited an increased proliferation rate.16 Our
study provides the clinical data predicted by these observations: reduced MTHFR activity due to the presence of
the T-allele of the c.677C.T variant is associated with
shorter overall survival. One limitation of our study was
that we did not know the folate intake or plasma folate
levels of the GBM patients, which might have modified
the effect of the MTHFR genotype on overall survival,
as the effect of the c.677C.T variant on MTHFR activity is modified by the availability of folate.11,17
Our findings may have some therapeutic implications.
Because the adverse biological effects of the T-allele of
the MTHFR c.677C.T variant, for example, on DNA
methylation, may well become apparent only in the context of a low folate status,17 folate supplementation or
dietary strategies influencing methionine and further
metabolites of methionine metabolism might be interesting candidate supportive therapies for GBM patients.
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Several tumor mutations have been correlated with
the clinical course of GBM patients.8 In addition, a few
studies have indicated that germline genetic variants
may have prognostic relevance, as well, for example,
the ERCC1 c.8092C .A polymorphism, the deletion
of glutathione S-transferase T1 (GSTT1),9 and a polymorphism in the 5'-untranslated region of the epidermal
growth factor gene (g.61G.A).10
The major finding of the present study is an association of the c.677TT genotype of the germline variant
MTHFR c.677C.T (A222V) with an adverse prognosis for GBM patients. Significant effects of the MTHFR
c.677C .T polymorphism were in particular seen in
patient subgroups with a comparatively good prognosis. In the subgroup of patients younger than 60 years,
the 6-month difference in median survival for patients
homozygous for the MTHFR c.677CC genotype versus
patients with the c.677TT genotype suggests that the
effect size contributed by the c.677C.T genotype is clinically relevant. Accordingly, the MTHFR c.677TT genotype was also associated with a poorer prognosis within
the patient subgroup with a postoperative Karnofsky
score >70 but not among patients with a worse performance status. The association of MTHFR c.677C.T
with overall survival did not show any therapy-specific
effect. Given the limitations of any association study,
our findings have to be reproduced in an independent
dataset.
The T-allele of MTHFR c.677C .T, in particular
when in the homozygous state, leads to clearly reduced
enzyme activity.11 Our findings may be explained by
an effect on nucleic acid synthesis and thus on chromosomal stability.1 In addition, a lack of MTHFR activity
can reduce the available SAM in several organs, including the CNS, and SAM is the key methyl group donor
for DNA methylation (Fig. 1).12 The T-allele of MTHFR
c.677C .T has already been reported to be associ-
Linnebank et al.: MTHFR variant and GBM survival
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