genetic analysis of the c677t and a1298c mthfr ...stâng comparativ cu cancerul de colon drept...
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GENETIC ANALYSIS OF THE C677T AND A1298C MTHFR POLYMORPHISMS IN A COHORT OF
ROMANIAN PATIENTS WITH SPORADIC COLORECTAL CANCER
15
C e r c e t a r ie x p e r i m e n ta le &
m edico-chirurgicale
)
Cercetãri Experimentale & Medico-Chirurgicale
Anul XIVl · Nr.1/2007 · Pag. 15-23
Abstract:Background: One of the mutated genes associated with a lower level of 5- MTHF necessary forDNA methylation and possibly implicated in the carcinogenesis of sporadic colorectal cancer(CRC) is the gene encoding the methylenetetrahydrofolate reductase enzyme (MTHFR).Objectives: to investigate the frequency of the C667T and A1298C MTHFR variants in patientswith sporadic CRC and controls; to establish the relative risk for sporadic CRC in association withthese two polymorphisms. Patients and methods: Genotyping of C677T and A1298C MTHFR polymorphisms using PCR-RFLP methods was done in 69 patients diagnosed with CRC and referred from the Surgical ClinicIII Cluj. Sixty seven individuals without any signs of malignancy formed the control group. Results: The CT677 and TT677 genotypes were greater in patients with sporadic CRC comparedto controls (34.78% vs. 25.37%, OR 1.57; 95% CI [0.74-3.28], p=0.23 and 8.69% vs. 4.47%, OR2.13; 95% CI [0.51-8.91], p=0.47, respectively). The 1298AC and CC1298 genotypes wereassociated with an OR of 1.63 (49.27% vs. 37.31%, 95% CI [0.82-3.23], p= 0.15) and 3.00 (4.34% vs. 1.49%, 95% CI [0.3-29.58], p=0.6) for sporadic CRC. Patients positive for C677T and A1298Cpolymorphisms have a higher frequency of colon cancer in the left side than in the right side(18.84% vs. 4.34%, OR 5.11, 95%CI [1.38-18.83], p< 0.01, and 23.18% vs. 10.14%, OR 2.67,95%CI [1.02-6.98], p=0.03, respectively). Moreover, patients positive for C677T and A1298Cpolymorphisms have a higher frequency of colon cancer than rectal cancer (34.78% vs. 18.84%,OR 2.3, 95%CI [1.05-5.01], p= 0.03, and 28.98% vs. 15.94%, OR 2.15, 95%CI [0.94-4.92], p=0.06, respectively). Conclusions: Our study confirms the relationship between MTHFR genotypes and sporadiccolorectal cancer. High risk individuals could benefit from effective prevention and treatmentwith 5- FU strategies in order to reduce the mortality of sporadic colorectal cancer.
Key Words:sporadic colorectal cancer, C677T, A1298C, PCR- RFLP
REZUMAT: Una dintre genele mutante asociate cu concentraþie scãzutã a 5- MTHF necesarpentru metilarea ADN ºi posibil implicatã în procesul de carcinogenezã în cancerul colorectal(CCR) sporadic este gena care codificã metilentetrahidrofolat reductaza (MTHFR). Obiective: de a investiga frecvenþa variantelor C677T ºi A1298C din gena MTHFR la pacienþii cuCCR sporadic ºi în lotul de control; de a stabili riscul relativ de a dezvolta CCR sporadic în asociere cu aceste douã polimorfisme. Material ºi metode: Genotiparea pentru C677T ºi A1298C utilizând metoda PCR- RFLP s-a fãcutîntr-un lot de 69 pacienþi diagnosticaþi cu CCR sporadic în Clinica Chirurgie III, Cluj. ªaizeci ºiºapte subiecþi fãrã semne de malignitate au format grupul de control.Rezultate: GenotipurileCT677 ºi TT677 au avut o frecvenþã mai mare în grupul de pacienþi cu CCR sporadic comparativcu lotul de control (34.78% vs. 25.37%, OR 1.57; 95% CI[0.74-3.28], p=0.23 ºi respectiv 8.69%vs. 4.47%, OR 2.13; 95% CI [0.51-8.91], p=0.47).
Lucia Maria Procopciuc1,
Gelu Osian2,
Liviu Vlad2 ,
Ileana Olteanu1
1- Department of Medical Biochemistry, University of Medicine and Pharmacy Cluj- Napoca2- Department of Surgery Clinic III, University of Medicine and Pharmacy Cluj- Napoca
Correspondence to: Lecturer Lucia Maria Procopciuc. E-mail: [email protected]
Introduction
Colorectal cancer (CRC) is the fourth most common
cancer- related death in the western world and was
ranked third, after lung and breast cancer in Romania in
2001. CRC has a genetic component, implicating
numerous candidate genes as susceptibility
factors(1).
Gene expression patterns, which are controlled by
mechanisms such as DNA methylation, have been
shown to be altered for a number of genes in patients
with different forms of cancer, including CRC (2).
Sporadic CRC appears in about 95% of the cases, the
combination of genetic and environmental risk factors
contributing to its development.
One of the mutated genes implicated in the
carcinogenesis of sporadic CRC could be the gene
encoding the methylenetetrahydrofolate reductase
enzyme (MTHFR). This catalyzes the synthesis of
5-methyltetrahydrofolate (5- MTHF), the methyl donor
for methionine synthesis and the precursor of
S-adenosylmethionine, the universal methyl donor for
methylation reactions (2). Thus, MTHFR is a central
enzyme in the remethylation of homocysteine to
methionine and is important for both DNA methylation
and synthesis (3).
MTHFR is highly polymorphic and the variant
genotypes result in decreased MTHFR enzyme activity
and lower plasma folate levels. The most studied
genetic variant in the MTHFR gene is the 677C >T
polymorphism located in the exon 4, converting alanine
to valine in the mature protein and associated with
reduced enzyme activity and elevated homocysteine
levels (4,5,6,7). The C677T MTHFR polymorphism
influences folate metabolism and intracellular
availability of folate metabolites for DNA methylation
and nucleotide synthesis (8). Individuals carrying the
TT genotype have less folate available for methylation
than CC homozygotes. Homozygous mutant individuals
for the C677T polymorphism have 30% of normal
MTHFR activity (approximately 10% of North
Americans are predisposed to mild
hyperhomocysteinemia and have reduced levels of
DNA methylation) (4). The relationship between the
MTHFR polymorphism and CRC is controversial. Some
researches have shown a reduced risk associated with
the C677T polymorphism but this protective effect
disappears in individuals with low folate intake or high
alcohol consumption (9-13).
Recently, a second common variant in the exon 7 of
the MTHFR gene, A1298C, causing a C to A
substitution, was characterized. This polymorphism
was associated with decreased enzyme activity,
homozygotes having approximately 60% of MTHFR
activity. Heterozygotes for both C677T and A1298C
mutations, approximately 15% of individuals, had
50-60% of MTHFR activity, lower than in single
heterozygotes for the C677T variant (14).
Objectives: We aim to investigate the frequency of
the common C667T and A1298C variants of MTHFR in
Romanian controls and patients with sporadic CRC.
We also want to establish whether these two
polymorphisms represent risk factors for sporadic CRC
in both women and men. We aimed to analyze the
relationship of these two polymorphisms with
histological forms and staging, trying to obtain a
relationship with the prognosis of these cases.
Materials and Methods
1.Patients
In order to test the hypothesis that the two
polymorphisms are implicated in the carcinogenesis of
sporadic CRC, we genotyped these in a case- control
study of 69 patients and 67 healthy controls from the
16
REZUMAT (continuare): Genotipurile AC1298 ºi CC1298 au fost asociate cu un factor de risc de 1.63 (49.27% vs. 37.31%,95% CI [0.82-3.23], p= 0.15) ºi respectiv de 3.00 (4.34% vs. 1.49%, 95% CI [0.3-29.58], p=0.6)de a dezvolta CCR sporadic. 10.14%, OR 2.67, 95%CI [1.02-6.98], p=0.03). Pacienþii pozitivipentru polimorfismele C677T ºi A1298C au dezvoltat cu o frecvenþã mai mare cancer de colonstâng comparativ cu cancerul de colon drept (18.84% vs. 4.34%, OR 5.11, 95%CI [1.38-18.83],p< 0.01, ºi respectiv 23.18% vs. Mai mult, pacienþii pozitivi pentru polimorfismle C677T ºiA1298C au dezvoltat cu o frecvenþã mai mare cancer de colon comparativ cu cancerul de rect(34.78% vs. 18.84%, OR 2.3, 95%CI [1.05-5.01], p= 0.03 ºi respectiv 28.98% vs. 15.94%, OR2.15, 95%CI [0.94-4.92], p= 0.06).Concluzii: Studiul nostru confirmã relaþia dintre genotipurile pentru MTHFR ºi cancerul colorectalsporadic. Indivizii cu risc crescut pot beneficia de metode eficiente de prevenþie ºi tratament cu 5- FU pentru reducerea mortalitãþii prin CCR sporadic.
Received for publication:
16.10.2006
Revised: 20.11.2006
Surgical Clinic III. Of the 69 patients with sporadic CRC,
35 were males (mean age 64.65 years; SD 9.31,
median 64, range 43- 83) and 34 were females (mean
age 61.94 years; SD 10.42, median 62, range 47- 82).
Of the 67 controls, 31 were males (mean age 60.38
years; SD 13.96, median 62, range 26- 78) and 36 were
females (mean age 60.25 years; SD 7.38, median 60.5,
range 43- 73). Eligibility criteria for both cases and
controls were: age 25–85 years; no individual history
of cancer and no familial history of cancer. Controls had
to be free of all polyps at colonoscopy. Indications for
colonoscopy were rectorrhagia, anemia, transit
disorders, subocclusion, occlusion by luminal stenosis,
or tenesmus. Case selection was randomized and the
studied population, Caucasians from the Transylvanian
region, was homogeneous, with a folate-poor diet.
The characteristics of the two groups (age, location
of the tumors, alcohol consumption, smoking status)
are shown in table 1.
Written informed consent was obtained from each
participant in the study and the study was approved by
the Ethical Committee of our University.
2.Methods
Genotyping of C677T and A1298C MTHFR
polymorphisms using PCR- RFLP methods
Genomic DNA was extracted from peripheral blood
leukocytes using the method of Lahiry (15).
Genomic DNA from all participants in this study was
amplified by polymerase chain reaction (PCR) in 25ml
reaction mixture containing 2.0mM magnesium
chloride, 200mM each dNTPs, 0.2mM of each primer,
17
CHARACTERISTICS PATIENTS
(N= 69)
CONTROLS
(N= 67)
Sex
females, number (%)
males, number (%)
34 (49.27%)
35 (50.72%)
36 (53.73%)
31 (46.28%)
Tumor location
Right side, number(%)
Left side, number (%)
Transverse, number (%)
Rectal, number(%)
13 (18.84%)
27 (39.13%)
5 (7.24%)
24 (34.78%)
-
-
-
-
Age (years) ±SD (median)
< 50, number (%)
51- 60, number (%)
61-70, number(%)
> 70 years, number (%)
63.31 ± 8.97
63
6 (8.69%)
22 (31.88%)
21 (30.43%)
20 (28.98%)
59.86 ± 11.91
61
8 (11.94%)
23 (34.32%)
24 (35.82%)
12 (17.91%)
Smoking status
Current smoker, number (%)
Smoker in the past, number(%)
Never smoker, number (%)
16 (23.18%)
3 (4.34%)
50 (72.46%)
16 (23.88%)
3 (4.47%)
48 (71.64%)
Alcohol consumption
yes, number(%)
no, number (%)
38 (55.07%)
31 (44.92%)
42 (62.68%)
25 (37.31%)
Table 1. Clinical characteristics of the two studied groups: patients with sporadic CRC and control individuals
500ng of genomic DNA and 2.0 units of Taq
polymerase (SIGMA). To amplify the polymorphic
C677T region, we used primers 677F 5’-
ACCCACAGAAAATGATGCCCAG-3’ and 677R 5’-
TGCCCCATTATTTAGCCAGGAG- 3’ (4). For the
polymorphic A1298C region of the MTHFR gene, PCR
primers 1298F 5’- CACTTTGTGACCATTCCGGTTT-3’
and 1298R 5’- CTTTGGGGAGCTGAAGGACTA- 3’ were
used (16). PCR was carried out in an Eppendorf
thermocycler with 5 minutes denaturation at 950C,
followed by 30 cycles of denaturation for 30 sec at
940C, annealing for 30 sec at 590C (C677T) or 600C
(A1298C), and extension for 1 min 30 sec at 720C. For
the C677T polymorphism, the amplified fragment was
of 198bp, while for the A1298C polymorphism, the
amplified fragment was of 163bp.
In order to detect the C677T polymorphism, the PCR
product was digested with HinfI restriction enzyme
(New England Biolabs). For the A1298C polymorphism,
the amplified fragment was digested with MboII
restriction enzyme (New England Biolabs). For
enzymatic digestion, 5ml of PCR product, 1ml of buffer
(HinfI or MboII) and 5U of restriction endonuclease
(U/5ml PCR) were mixed and incubated for 3 h at 370C.
Digested DNA products were separated by
electrophoresis in a 3% agarose gel stained with
ethidium bromide. After enzymatic digestion, the
198bp fragment gave for the wild-type allele (C677) an
undigested fragment of 198bp and for the mutated
allele (T677) two fragments of 175 and 23bp (figure 1).
For the wild- type allele (A1298), the 163bp amplified
fragment gave after enzymatic digestion the 84, 31, 30,
28bp fragments, while for the mutated allele (C1298),
the 163bp amplified fragment gave the 56, 31, 30 and
28bp fragments (figure 2).
Statistical analysis
Genotype frequencies were compared using the
chi2 test. Odds ratio (OR) and 95% confidence intervals
(95%CI) were calculated to assess the strength of the
relationship between the C677T and A1298C
polymorphisms and sporadic CRC. We evaluated the
association between MTHFR genotypes and sporadic
CRC first in the entire study population and
subsequently separately in men and women.
18
Figure 2. Restriction analysis of the A1298C MTHFR
polymorphism. Lane 1- pBRHaeIIIDigest DNA molecular marker; Lane
2- 163bp amplified fragment; Lane 3- homozygous negative patient:
fragment of 84bp; Lane 4- heterozygous patient: fragment of 84 and
56bp; Lane 5- homozygous positive patient: fragment of 56bp
Figure 1. Restriction analysis of the C677T MTHFR polymorphism.
Lane 1- pBRHaeIIIDigest DNA molecular marker; Lane 2- 198bp
amplified fragment; Lane 3,4- heterozygous patients: fragments of
198 and 175bp; Lane 5- homozygous negative patients: undigested
fragment of 198bp; Lane 6- homozygous positive patients: fragment
of 175bp
RESULTS
In order to investigate the role of
methylenetetrahydrofolate reductase gene
polymorphisms in sporadic CRC carcinogenesis, we
analyzed the genotypes of C677T and A1298C MTHFR
of 69 patients with this diagnosis and 67 healthy
controls with negative colonoscopy, using a
polymerase chain reaction restriction fragment length
polymorphism method (PCR- RFLP). There was a
difference in genotype distribution and allele frequency
between patients with sporadic CRC and controls. In
patients with sporadic CRC (39 CC homozygotes, 6 TT
homozygotes, 24 CT heterozygotes) the allele
frequency of the T allele was 0.26 compared to 0.17 in
controls (47 CC homozygotes, 3 TT homozygotes, 17
CT heterozygotes). Concerning the A1298C
polymorphism, the results showed that in patients with
sporadic CRC (32 AA homozygotes, 3 CC
homozygotes, 34 AC heterozygotes) the allele
frequency of the C allele was 0.28 compared to 0.2 in
controls (41 AA homozygotes, 1 CC homozygotes, 25
AC heterozygotes) (table 2).
DISCUSION
Sporadic CRC is a multifactorial disease, many
factors contributing to its development, including on
the one hand dietary habits and on the other hand
genetic predisposition (17). Methylenetetrahydrofolate
19
A1298C (Glu ÷ Ala) Allelic frequency
AA (%) AC (%) CC (%) A C
Cases 32 (46.37%)34
(49.27%)3 (4.34%) 0.71 0.28
C677T (Ala÷ Val)
CC (%)
39 (56.52%)17 (24.63%)
20(28.99%)
2 (2.89%)
CT (%)
24 (34.78%)10 (14.49%)
20(28.99%)
2 (2.89%)
TT (%)
6 (8.69%)5 (7.24%) 1 (1.49%) -
Allelic frequencyC 0.73
T 0.26
Controls (N=67) 41 (61.19%)25
(37.31%)1 (1.49%) 0.79 0.2
C677T
(Ala ÷ Val)
CC (%)
47 (70.14%)30 (44.77%)
16(23.88%)
1 (1.49%)
CT (%)
17 25.37%)10 (14.49%) 7 (10.44%) -
TT (%)
3 (4.47%)2(2.98%) 1(1.49%) -
Allelic frequencyC 0.83
T 0.17
Table 2. Alleles and genotypes distribution of C677T and A1298C MTHFR in patients with sporadic
CRC and in control subjects
reductase is a key enzyme in folate metabolism, which
affects DNA synthesis and methylation and is possibly
linked to colorectal carcinogenesis (18). Moreover, the
C677T and A1298C variants have been linked to the
development of most cancers and leukemias (19-21).
Both have been associated with the efficacy and side
effects of cytotoxic drugs like methotrexate and 5-FU
(22,23).
In our study, the CT677 and TT677 genotypes were
greater in patients with CRC compared to controls
(34.78% vs. 25.37%, OR 1.57; 95% CI [0.74-3.28], p=
0.2 and 8.69% vs. 4.47%, OR 2.13 95% CI [0.51-8.91];
p=0.4, respectively). An increased cancer risk was
observed in TT homozygotes. The results were close to
those obtained by Levine (2000) concerning the
association between the TT genotype and the risk for
distal colorectal adenoma (24). The results concerning
the relative risk to develop sporadic CRC in
heterozygotes for the C677T polymorphism were close
to the results obtained by Ryan (2001) (25).
Concerning the second polymorphism, the 1298AC
genotype was associated with an OR of 1.63 (49.27%
vs. 37.31%, 95% CI [0.82-3.23], p= 0.1) for sporadic
CRC, while the CC1298 genotype was associated with
an OR of 3.00 (4.34% vs. 1.49%, 95% CI [0.3-29.58],
p=0.6). The distribution of AC genotype in sporadic
CRC was close to that reported by Toffoli (2003) (26).
Colon cancer occurs with an approximately equal
frequency in men and women (26). Some of the
researches show that the risk of CRC conferred by
MTHFR genotypes may differ between individuals
depending on sex. The analysis of the C677T
polymorphism in women with sporadic CRC vs. control
women indicated that the relative risk to develop
sporadic CRC in heterozygous or homozygous carriers
was1.41 (38.23% vs. 30.55%, 95%CI, [0.52-3.78],
p=0.49) and 2.27 (11.76% vs. 5.55%. 95%CI, [0.38-
13.26], p= 0.6), respectively. The analysis of the
C677T polymorphism in males with sporadic CRC vs.
control males indicated that the relative risk to develop
sporadic CRC in heterozygous or homozygous carriers
was 1.91 (31.42% vs. 19.35%, 95%CI, [0.6- 5.98], p=
0.26) and 1.82 (5.71% vs. 3.22%. 95%CI, [0.15- 21.08],
p= 0.9), respectively.
Concerning the A1298C polymorphism, women
heterozygous or homoyzgous for A1298C MTHFR had a
2.24 (55.88% vs. 36.11%, 95%CI, [0.85- 5.85], p=
0.09) and 1.06 (2.94% vs. 2.77%, 95%CI, [0.06- 17.65],
p= 0.4), respectively increased risk for sporadic CRC.
In heterozygous males patients the relative risk to
develop sporadic CRC was 1.19 (42.85% vs. 38.7%,
95%CI, [0.44- 3.18], p= 0.7). We found homozygotes
for A1298C only among patients with sporadic CRC,
5.71%(table 3).
Some researches have shown that there are
differences concerning the location of the tumors and
the genotype for C677T and A1298C polymorphisms
(26). Our preliminary results showed that patients
positive for C677T and A1298C polymorphisms had a
higher risk to develop colon cancer in the left side than
in the right side (18.84% vs. 4.34%, OR 5.11, 95%CI
[1.38- 18.83], p< 0.01, and 23.18% vs. 10.14%, OR
2.67, 95%CI [1.02-6.8], p= 0.03, respectively).
20
GenotypePatients
69 (50.73%)
Controls
67 (49.26%)OR, 95%IC p
C677T MTHFR (Ala÷ Val)
CT
TT
T677 mutated allele
43.47%
34.78%
8.69%
36 (0.26)
29.85%
25.37%
4.47%
23 (0.17)
1.81 [0.89-3.66]
1.57 [0.74-3.28]
2.13 [0.51-8.91]
0.09
0.2
0.4
A1298C MTHFR (Glu÷ Ala)
AC
CC
C1298 mutated allele
53.62%
49.27%
4.34%
40 (0.28)
38.18%
37.31%
1.49%
27 (0.2)
1.82 [0.92-3.6]
1.63 [0.82-3.23]
3.00 [0.3-29.58]
0.08
0.1
0.6
Table 3. The relative risk to develop sporadic CRC. Comparison between patients and controls
OR- odds ratio; 95%CI- 95% confidence intervals; p- statistical significance means p< 0.05
Moreover, patients positive for C677T and A1298C
polymorphisms had a higher risk to develop colon
cancer than rectal cancer (28.98% vs. 15.94%, OR
2.15, 95%CI [0.94-4.92], p= 0.06 and 34.78% vs.
18.84%, OR 2.3, 95%CI [1.05- 5.01], p= 0.03,
respectively).
The potential interaction between C677T MTHFR and
A1298C MTHFR polymorphisms on the risk of sporadic
CRC was further examined (patients vs. controls). For
individuals carrying both CC677 and AC1298 the OR
was 1.21 (28.99% vs. 23.88%), while the risk increased
to 1.93 in patients with both CC677 and CC1298
(2.89% vs. 1.49%) genotypes. Patients positive for both
CT677 and AC677 had a relative risk of 1.66 (17.39%
vs. 10.44%) to develop sporadic CRC. An increased risk
was observed for patients positive for both TT677 and
AA1298 genotypes, 2.43 (7.24% vs. 2.98%). A
protective effect was observed for patients carrying
both CC677 and AA1298 genotypes, OR 0.56 (24.63%
vs. 43.28%). We found a complete absence of TT677
and CC1298 genotypes; the results were in agreement
with those obtained by Weisberg (1998) and Skibola
(1999) (14, 27).
Regarding the relationship of the C677T genotype
with the Dukes-Mac stage, the study shows that 60%
of stage D patients are patients with the C677T
mutation, present in heterozygous or homozygous
form. The results also show an increase in incidence
for stage D (60%) compared to stage C (34.7%,
p=0.33) and B (46.66%, p=0.71), respectively. In all
cases p>0.05 (table 4).
Regarding the relationship of the A1298C mutation
with cancer staging, our study shows that 70% of
stage D patients are patients with the A1298C
mutation in heterozygous or homozygous form. The
carriers of the A1298C mutation had more frequently
stage D than stage B (70% vs. 60%, p=0.85) and stage
C (70% vs. 26.09%, p=0.04), respectively (table 5).
CONCLUSIONS
Our study showed an association of MTHFR
genotypes with sporadic CRC. We found an elevated
risk of sporadic CRC associated with the heterozygous
and homozygous genotypes of the MTHFR 677>C T
and MTHFR 1298A>C polymorphisms, respectively.
The results confirm the hypothesis that methylation of
DNA may be important in the etiology of sporadic CRC,
because DNA methylation influences cellular
development and function, and aberrations of DNA
methylation are a candidate mechanism for the
development of cancer.
There is evidence that diets low in vegetables and
fiber, with low folate intakes, are associated with an
increased risk for colorectal cancer (29). When folate
levels are low (low intake or depletion by alcohol
consumption) both DNA methylation and synthesis
might be impaired in carriers of MTHFR mutations,
resulting in an increased risk for colorectal cancer (30).
21
Genotype A B C D p
AA 1 (16.66%) 12 (40%) 17 (73.9%) 3 (30) C vs. B- 0.02
AC+ CC 5 (83.33%) 18 (60%) 6 (26.09%) 7 (70%)
B vs. C- 0.01
D vs. C- 0.04
D vs. B- 0.85
Table 5. Relationship of A1298C genotype with Dukes-Mac stage
Genotype A B C D p
CC 3 (50%) 16 (53.3%) 15 (65.2%) 4 (40%)
CT + TT 3 (50%) 14 (46.66%) 8 (34.7%) 6 (60%)D vs. C- 0.33
D vs. B- 0.71
Table 4. Relationship of C677T genotype with Dukes-Mac stage
In our study we have no data on folate intake, but the
population from this geographic area presents several
nutritional risk factors such as high protein and animal
fat and lower fiber diets, lower folate intake, which
reduces the protection conferred by the TT677 and
CC1298 genotypes.
Considerable work has already been focused on
genotype differences in the response to drug
treatments, in order to develop treatment modalities
for individuals identified positive for the C677T and
A1298C mutations. High risk individuals could benefit
from effective prevention and treatment with 5-FU
strategies in order to reduce the mortality of sporadic
colorectal cancer.
Acknowledgments. This study was supported bya grant from the Ministry of Education.
22
REFERENCES1. Kemp Z, Thirlwell C, Sieber E, Silver A, Tomlinson I.- An update on the genetics of colorectal cancer, Human Molecular
Genetics. 2004; 13 (2): R177-R185
2. Kim Y- I. Folate and carcinogenesis: Evidences, mechanism and implications. J Nutr Biochem 1999; 10: 66-88
3. Banerjee RV, Matthews R-G.- Cobolamine dependent methionine synthase, FASEB J. 1990; 4: 1450- 1459
4. Frosst P, Blom HJ, Millos R.- A candidate genetic risk factor for vascular disease: a common mutation in
methylenetetrahydropholate reductase, Nat Genet. 1995;10: 111-113
5. Jacques PF, Bostom AG, Williams RR.- Relation between folate status, a common mutation in methylenetetrahydrophoilate
reductase and plasma homocysteine concentration, Circulation. 1996; 93: 7-9
6. Ma J, Stampfer MJ, Hennekens CH.- Methylenetetrahydropholate reductase polymorphism, plasma folate, homocysteine and
risk of myocardial infarction in USA physicians, Circulation. 1996; 94: 2410- 2416
7. Stern L, Mason J, Selhub J.- Genomic DNA hypomethylation and the characteristics of most cancers is present in peripheral
leukocytes in individuals who are homozygous for the C677T polymorphism in the methylenetetrahydropholate reductase gene,
Cancer Epidemiol Biomarkers Prev. 2000; 9:849- 853.
8. Fearon ER, Vogelstein BA.- A genetic model for colorectal tumorogenesis, Cell. 1990; 61: 759- 767
9. Chen J, Giovannuci E, Kelsey K.- A methylenetetrahydropholate reductase gene polymorphism and the risk of colorectal
cancer, Cancer Res. 1996; 56: 4682- 4684
10. Park K, Mok J, Kim J.- The C677> T mutation in 5,10- methylenetetrahydropholate reductase and colorectal cancer risk, Genet
Test. 1999; 3: 233-236
11. Ulrich CM, Kampman E, Bigler J.- Colorectal adenomas and the C677T MTHFR polymorphism: evidence for gene- environment
interaction?, Cancer Epidemiol Biomark Prev. 1999; 8: 659-668
12. Ma J, Stampfer M J, Giovannucci.- Methylenetetrahydrofolate reductase polymorphism, dietary interactions, and risk of
colorectal cancer, Cancer Res. 1997; 57: 1098-1102
13. Slaterry M, Potter J, Samowitz W.- Methylenetetrahydropholate reductase, diet and risk of colon cancer, Cancer Epidemiol
Biomark Prev. 1999; 8: 513-518
14. Weisberg I. -A second genetic polymorphism in MTHFR associated with decreased enzyme activity, Mol Genet Metab. 1998;
64(3):169-72
15. Lahiry DK, Nurnberger JI.Jr.- A rapid non- enzymatic method for the preparation of HMW DNA from blood for RFLP studies,
Nucleic Acids Res. 1991; 19: 5444
16. van der Put NMJ, Gabreels F, Stevans EMB.- A second common mutation in the methylenetetrahydropholate reductase
gene: An additional risk factor for neural tube defects?, Am J Hum Genet. 1998; 62: 000-000
17. de Jong MM, Nolte IM, te Meerman GJ.- Low penetrance genes and their involvement in Colorectal cancer susceptibility,
Cancer Epidemiol Biomark Prev. 2002; 11: 1332-1352
18. Duthie SJ, Narayanan S, Blum S.- Folate deficiency in vitro induces uracil misincorporation and DNA hypometilation and
inhibits DNA excision repair in immortalized normal human colon epithelial cells, Nutr Cancer. 2000; 37: 245-251
19. Matsuo K.- MTHFR gene polymorphisms and reduced risk of malignant lymphoma. Am J Hematol. 2004;77(4):351-7
20. Cicek MS.- Relationship between MTHFR C677T and A1298C genotypes and haplotypes and prostate cancer risk and
aggressiveness, Cancer Epidemiol Biomarkers Prev. 2004;13(8):1331-6
21. Krajinovic M.- Role of MTHFR genetic polymorphisms in the susceptibility to childhood acute lymphoblastic leukaemia, Blood.
2004;103(1):252-7
22. Berkun Y.- Methotrexate related adverse effects in patients with rheumatoid arthritis are associated with the A1298C
polymorphism of the MTHFR gene, Ann Rheum Dis. 2004; 63(10):1227-31
23. Etienne MC.- Thymidylate synthase and MTHFR gene polymorphisms: relationships with 5-fluorouracil sensitivity, Br J Cancer.
2004; 90(2):526-34
23
REFERENCES (continued)
24. Levine AJ, Siegmund KD, Ervin CM. The Methylenetetrahydrofolate Reductase 677CT Polymorphism and Distal Colorectal
Adenoma Risk, Cancer Epidemiology Biomarkers & Prevention. 2000; 9: 657-663
25. Ryab BM, Molloy AM,McManus R. - The methylenetetrahydrofolate reductase (MTHFR) gene in colorectal cancer: role in
tumor development and significance of allelic loss in tumor progression, Int J Gastrointest Cancer 2001; 30(3):105-11
26. Toffoli G, Gafa R, Russo A.- Methylenetetrahydropholate reductase 677T÷C polymorphism and risk of proximal colon cancer in
North Italy, Clinical Cancer Res. 2003; 9: 743- 748
27. Skibola CF, Smith MT, Kane E.- Polymorphism in methyleneteytrahydropholate reductase gene are associated with
susceptibility to acute leukemia in adults, Proc. Natl Acad Sci USA.1999; 96: 12810- 12815
28. Matsuo K, Ito H, Wakai K.- One-carbon metabolism related gene polymorphisms interact with alcohol drinking to influence
the risk of colorectal cancer in Japan, Carcinogenesis. 2005 26(12):2164-2171
29. Boutron R, Senesse P, Meance S.- Energy intake, body mass index physical activity and the colorectal adenoma sequence,
Nutr Cancer. 2001; 39: 50-57
30. Giovannuci E, Rimm EB, Ascherio A.- Alcohol- low- methionine- low folate diets and risk of colon cancer in men., J Natl Cancer
Inst (Bethesada). 1995; 87: 265- 273
Bucharest - Romania
17th World Congress of the International Association of Surgeons,
Gastroenterologists and Oncologists