Abstract
Introduction
Carcinogenesis is a genetic disease at the cellular level. It is a case of irreversible
loss of gene regulation, which controls growth and differentiation. This event is due to
changes in DNA and the cancer cells show uncontrolled mitotic activity, which makes
these cells to look more like immature cells rather than normal mature differentiated
cell types, since they produce proteins found in embryonic cells. In every normal cell
there is a normal level for protein production. Disruption of gene regulation and
expression because of mutations or DNA polymorphisms may change the normal
protein level. Like other types of cancer, oral squamous cell carcinoma (OSCC) is related
to the coagulation system. Thromboembolism is one of the most frequent causes of
death in patients with cancer. It is therefore clear that such complications occur as the
cancer cells have participated in almost all factors of the haemostatic system. Given the
above, in this dissertation mutat ...
Introduction
Carcinogenesis is a genetic disease at the cellular level. It is a case of irreversible
loss of gene regulation, which controls growth and differentiation. This event is due to
changes in DNA and the cancer cells show uncontrolled mitotic activity, which makes
these cells to look more like immature cells rather than normal mature differentiated
cell types, since they produce proteins found in embryonic cells. In every normal cell
there is a normal level for protein production. Disruption of gene regulation and
expression because of mutations or DNA polymorphisms may change the normal
protein level. Like other types of cancer, oral squamous cell carcinoma (OSCC) is related
to the coagulation system. Thromboembolism is one of the most frequent causes of
death in patients with cancer. It is therefore clear that such complications occur as the
cancer cells have participated in almost all factors of the haemostatic system. Given the
above, in this dissertation mutations or polymorphisms were studied in genes whose
protein products are associated with a) blood clotting (methyletetrahydrofolare
reductase, factor V, prothrombin, factor XII, factor XIII, protein Z), b) the fibrinolysis
system (plasminogen activator inhibitor-1, thrombin activated fibrinolysis inhibitor) and
c) the renin-angiotensin system (angiotensin converting enzyme, angiotensinogen).
Materials and Methods
The C677T mutation in Methyletetrahydrofolate reductase gene (MTHFR), the
Leiden mutation in the gene of factor V (FV), the G20210A mutation in the Prothrombin
gene (PT), the C46T polymorphism in the gene of Factor XII (FXII), the V34L
polymorphism in the gene of Factor XIII (FXIII), the polymorphism -13A/G in the
Protein Z gene (PZ), the 4G/5G insertion/deletion polymorphism in the Plasminogen
Activator Inhibitor-1 gene (PAI-1), the polymorphism 1040 C/T in the Thrombin
Activatable Fibrinolysis Inhibitor gene (TAFI), the insertion/deletion polymorphism in
Angiotensin-Converting Enzyme gene (ACE) and the M235T polymorphism in
Angiotensinogen gene (AGT) were studied in 163 DNA samples from patients with oral
squamous cell carcinoma and 168 samples from healthy controls with corresponding
age and gender. Results
For the C677T polymorphism in MTHFR gene the data of the present study revealed
a statistically significant increase of T allele heterozygotes in the patients group (P=
0,043). This result seems to arise only in the subgroup of patients with a history of
thrombophilia where the heterozygotes for the T allele was also significantly increased
(P = 0,034).
The overall data obtained for the Leiden mutation in the FV gene and the G20210A
mutation in the PT gene revealed no statistically significant differences in the
comparisons made between the control group and the patient’s group and subgroups.
The overall data obtained for the C46T polymorphism of the FXII gene revealed a
statistically significant reduction in homozygous patients P=0,008. Similarly statistically
significant reductions of heterozygotes occurred in subgroups of patients with advanced
stage of cancer, family history of thrombophilia and without tobacco abuse, always in
relation to the control group.
In the group of healthy controls (N = 135), the V34L mutation in the gene of FXIII
was found in 6 homozygotes (4.44%) and 48 heterozygotes (35.56%), while in the
group of patients (N = 130) there were 12 homozygotes (9.23%) and 62 heterozygotes
(47.69%). This data reveals an incriminatory role for the L allele in the development of
OSCC. The same pattern appears in the subgroups of patients with early cancer stage,
without family history of cancer, without family history of thrombophilia, without
tobacco abuse and without alcohol abuse.
For the polymorphism-13A / G in the PZ gene, no statistically significant differences
were shown between the group of healthy controls and the group of patients. The same
picture appeared in the comparisons made between healthy controls and the various
subgroups of patients.
For the 4G/5G insertion/deletion polymorphism of the PAI-1 gene the overall data
revealed statistically significant increase of homozygotes and heterozygotes in the
patient group (P=0,001 and P=0,009 respectively) compared to the control group. This
appearance of 4G allele as an incriminatory factor is confirmed by various subgroups of
patients. Specifically, by the subgroup of patients with early stage of cancer, the
subgroup of patients without family history of cancer, the subgroup of patients without
family history of thrombophilia, the subgroup of patients with tobacco abuse and the
subgroup of patients without alcohol abuse.
For the polymorphism 1040C/T in the TAFI gene, in the group of healthy controls
(N = 138), the mutant T allele was found in 18 homozygotes (13.04%) and 66 heterozygous (47.83%), while in patients group (N = 150) the homozygotes were 8
(5.33%) and the heterozygotes 70 (46.67%). These figures reveal a significant
reduction in homozygotes (P = 0,018), while the values of OR=0,29 (less than one) and
95% CI (0,11-0,74) assign to this particular allele a protective role against the
development of OSCC. This protective role of the T allele was reflected in the
comparisons that took place between healthy controls and the homozygotes in the
subgroups of patients with advanced cancer stage, with tobacco abuse, without
tobacco abuse and without alcohol abuse.
For the insertion/deletion polymorphism in the ACE gene this study revealed a
statistically significant increase of homozygotes in the patients group compared with the
control group. This increase of homozygotes is also reflected in the comparisons
occurred between healthy controls and homozygotes in the subgroups of patients with
early stage of cancer, with advanced stage of cancer, without family history of cancer,
without family history of thrombophilia, without tobacco abuse and without alcohol
abuse.
For the M235T polymorphism of AGT gene the overall data of this study showed
that the prevalence of 'mutant' high expression T allele was not significantly different in
the total patient’s group and almost in any of the subgroups, compared to healthy
controls. Only in the subgroup of patients with a family history of cancer the
homozygotes and the heterozygotes are significantly higher than in the control group.
The findings of the multivariate logistic regression for the overall cancer stages of
OSCC of model A (mutant homozygotes) highlight as important independent factors in
tumor development: a) age, b) gender, c) the genotype I/I of the I/D polymorphism in
the ACE gene and d) the 4G/4G genotype of the 4G/5G polymorphism in the PAI-1
gene, while the same model for the early and late stages of OSCC includes only the first
three factors.
Model B (mutant heterozygotes) for the overall stages of OSCC highlights as
important independent factors in tumor development: a) age, b) sex and c) the 4G/5G
genotype of the -675 4G/5G polymorphism in the PAI-1 gene. The same model for the
early stages of OSCC includes a) age, b) sex and also c) heterozygotes for the C677T
polymorphism in the MTHFR gene. Finally, in the late stages of OSCC Model B includes
the factors a) age, b) sex and also c) heterozygotes of the C46T polymorphism in the
FXII gene, and d) heterozygotes of the V34L polymorphism in the FXIII gene. Model C (inheritance mode of mutations) shows as significant independent
determinants of growth of tumor in the mouth: a) age, b) sex and c) the genotype I/I
of the I/D polymorphism in the ACE gene.
Conclusions
Of the total 10 polymorphisms or mutations investigated in this study 3 did not
show any correlation with the development of OSCC, 2 shows moderate correlation, 2
have a protective effect and 3 are closely related with the development of OSCC.
Leiden mutation in the gene of factor V (FV), G20210A mutation in prothrombin
gene (PT) and the -13A/G polymorphism in the gene of protein Z (PZ) does not affect
oral oncogenesis.
The C677T polymorphism in the gene of methyletetrahydrofolate reductase
(MTHFR) and the M235T polymorphism in the angiotensinogen (AGT) gene
demonstrated mild incriminatory role in the oral cavity oncogenesis.
The mutant alleles of the C46T polymorphism in the gene of Factor XII (FXII) and
the 1040C/T polymorphism in the thrombin activatable fibrinolysis inhibitor (TAFI) have
a protective effect in terms of OSCC development.
The V34L polymorphism in the gene of factor XIII (FXIII), the 4G/5G polymorphism
in the plasminogen activator inhibitor -1 gene (PAI-1) and the insertion/deletion
polymorphism in the angiotensin-converting enzyme (ACE) gene are closely related with
the development of OSCC.
Model A (mutant homozygotes) for the overall stages of OSCC highlights as
important independent factors in tumor development: a) age, b) gender, c) the
genotype I/I of the I/D polymorphism of ACE gene and d) genotype 4G/4G of the
4G/5G polymorphism in the PAI-1 gene, while the same model for the early and late
stages of OSCC includes only the first three factors.
Model B (mutant heterozygotes) for the overall stages of OSCC highlights as
important independent factors in tumor development: a) age, b) sex and c) the 4G/5G
genotype of the -675 4G/5G polymorphism in the PAI-1 gene. The same model for the
early stages of OSCC includes a) age, b) sex and also c) heterozygotes for the C677T
polymorphism in the MTHFR gene. Finally, in the late stages of OSCC Model B includes
the factors a) age, b) sex and also c) heterozygotes for the polymorphism C46T in the
FXII gene, and d) heterozygotes for the polymorphism V34L in the FXIII gene.
Model C (inheritance mode of mutations) reveals a) age, b) sex and c) the
genotype I/I of the I/D polymorphism in the ACE gene as significant independent
determinants of tumour growth in the mouth. The possibility of molecular detection of ACE polymorphism associated with
increased risk for AKS may contribute to AKS prevention in the general population.
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