Serum levels of zinc, copper, selenium and glutathione peroxidase in the different groups of colorectal cancer patients

Abstract

Background: Colorectal cancer (CRC) is considered the fourth type of cancer that causes death in the world. Changes in levels of Zinc (Zn), Copper (Cu), and Selenium (Se) as well as low glutathione peroxidase (GPx) activity can lead to CRC and this study was aimed to evaluate their possible use as diagnostic markers.
Methods: CRC patients (n=90) were divided into three groups; newly diagnosed, before surgery, and after surgery. These groups were compared to healthy subjects (n=30); the mean age ±SD was 50.63±9.26 and 49.97 ±10.85 for CRC patients and healthy subjects, respectively. Biochemical study for serum levels of Zn and Cu were measured by FAAS, Se was measured by HGAAS, and ELISA for GPx.
Results: Zn, Cu, Se and GPx were significantly lower in all CRC patient groups, except for the after surgery group which showed no differences for Zn and GPx as compared to the healthy subjects. Positive correlations were found between Se and Zn and between Se and GPx (r = 0.71, r = 0.42; P < 0.01, respectively) in all CRC patient groups. A receiver operating characteristic (ROC) curve analysis applied for the newly diagnostic group showed that all parameters can be used as diagnostic markers for CRC.
Conclusion: The present results conclude that Zn, Cu Se, and GPx can be used as diagnostic markers for CRC, where the decrease of these parameters may be associated with an increased risk of CRC and as indicators of the response to therapy.

Full text

Caspian J Intern Med 2020; 11(4):384-390
DOI: 10.22088/cjim.11.4.384
Original Article
Copyright © 2020, Babol University of Medical Sciences
This open-access article distributed under the terms of the Creative Commons Attribution-Noncommercial 4.0
Raghad F. Al-ansari (MSc) 1
Abdulnasser M. AL-Gebori
(PhD) 1
Ghassan M. Sulaiman (PhD) 2*
1. Applied Chemistry Division,
Applied Science Department,
University of Technology,
Baghdad, Iraq
2. Biotechnology Division, Applied
Science Department, University of
Technology, Baghdad, Iraq
* Correspondence:
Ghassan M. Sulaiman,
Biotechnology Division, Applied
Science Department, University of
Technology, Baghdad, Iraq
E-mail: gmsbiotech@hotmail.com
Tel: 0096 49702781890
Received: 15 Sep 2019
Revised: 9 Feb 2020
Accepted: 16 Feb 2020
Serum levels of zinc, copper, selenium and glutathione
peroxidase in the different groups of colorectal cancer patients
Abstract
Background: Colorectal cancer (CRC) is considered the fourth type of cancer that causes
death worldwide. Changes in the levels of zinc (Zn), copper (Cu), and selenium (Se) as well
as low glutathione peroxidase (GPx) activity can lead to CRC and this study was aimed to
evaluate their possible use as diagnostic markers.
Methods: CRC patients (n=90) were divided into three groups; newly diagnosed, before
surgery, and after surgery. These groups were compared to healthy subjects (n=30); the
mean age ±SD was 50.63±9.26 and 49.97±10.85 for CRC patients and healthy subjects,
respectively. Biochemical study for serum levels of Zn and Cu was measured by FAAS, Se
was measured by HGAAS, and ELISA for GPx.
Results: Zn, Cu, Se and GPx were significantly lower in all CRC patient groups, except for
the after surgery group which showed no differences for Zn and GPx as compared to the
healthy subjects. Positive correlations were found between Se and Zn and between Se and
GPx (r=0.71, r=0.42; P<0.01, respectively) in all CRC patient groups. A receiver operating
characteristic (ROC) curve analysis was applied for the newly diagnostic group showing all
the parameters that can be used as diagnostic markers for CRC.
Conclusion: The present results conclude that Zn, Cu Se, and GPx can be used as diagnostic
markers for CRC, where the decrease of these parameters may be associated with an
increased risk of CRC and as indicators of the response to therapy.
Keywords: Colorectal cancer, Zn, Cu, Se, GPx, Serum.
Citation:
Al-ansari R, Al-Gebori A, Sulaiman G. Serum levels of zinc, copper, selenium and glutathione
peroxidase in the different groups of colorectal cancer patients. Caspian J Intern Med 2020; 11(4):
384-390.
Colorectal cancer (CRC) is considered as the fourth cause of death among types of
cancer globally. It is also ranked third among the most commonly diagnosed types of cancer
(1). CRC refers to malignant epithelial neoplasms that occur in the colon and/or the rectum
by transforming epithelial cells into adenocarcinoma cells (2). Zinc (Zn), copper (Cu), and
selenium (Se) are essential dietary nutrients for the body and are implicated in cancer risk, where
they act as anti-oxidant agents. Zn catalyzes the activity of more than 300 enzymes and has roles
in the immune function, DNA synthesis, protein synthesis, and cell division. It is also
responsible for the maintenance of the structure of DNA and its binding to more than 1000
transcription factors that are required for gene expression of many proteins. Cu plays an
important function in preserving the integrity of DNA by preventing oxidative DNA damage.
Many enzymes and proteins in humans depend on Zn, Cu and Se. Both Zn and Cu play the
main role in the activity of the antioxidant enzyme known as copper-zinc superoxide dismutase.
Se also contributes to the formation of some enzymes such as glutathione peroxidase (GPx),
thioredoxin reductase (TrxR) and iodothyronine deiodinases (IDD) which act as anti-oxidant
enzymes.

Caspian J Intern Med 2020; 11(4): 384-390
Trace elements and glutathione peroxidase in serum of colorectal cancer patients 385
It has also an important role in the protection against
oxidative stress through the action of antioxidant
selenoproteins against reactive oxygen species (ROS) and
reactive nitrogen species (NOS). Together, H2O2, O2−, and OH
radicals form the ROS, the excessive generation of which
causes oxidative stress. Many diseases, such as cancer, can
develop as a result of oxidative stress, if there is an imbalance
between the defense antioxidant system of the cell and the
generation of ROS species (3-8).
A previous study on CRC patients showed that the serum
level of Se decreased while Zn level increased, while it
showed no difference in the level of Cu (9). Zn deficiency
appeared in colon cancer patients, whereas Cu showed no
difference compared with the healthy controls in a Saudi
population (10). Iraqi patients with colon cancer also showed
a decrease in Zn and an increase in Cu levels (11). The same
findings were also reported in CRC patients in Brazil (12).
Another recent study has reported that both Zn and Cu
decreased in Iranian CRC patients (13).
GPx (EC 1.11.1.9) is an enzyme that is classified as
oxidoreductase which catalyzes the reduction of the organic
hydroperoxides or H2O2 to corresponding alcohols or water
using reduced glutathione. Some GPx isozymes are described
as selenium-dependent (14). Previous studies reported that
GPx activity in colon cancer patients was lower in the plasma
and serum as compared to the control (15, 16).
Several factors are involved in the process of CRC
treatment, including the disease stage; about 95% of stage I
and 65-80% of stage II patients can only be treated via
surgery. However, several types of treatment such as chemo-
and radiotherapy can be applied to patients in stages III and
IV before having to undergo surgery (17). The ability of
cancer cells to spread to other tissues, including lymph nodes,
was well documented, while the rate of this process as well as
the speed of cancer cells growth are correlated with the
disease grades that are classified into G1, G2, and G3
according to severity (18).
Hence, the previous investigations conducted on the
relationships between Zn and Cu with CRC are controversial
as to whether these elements increased or decreased in the
serum of the patients. Also, the cutoff values of these
parameters were not defined by previous studies. In this study,
we assessed the levels of these parameters in different groups
of CRC patients and determined the cutoff values that could
be applied for newly diagnostic patients. Also, we analyzed
the correlations among the investigated elements.
Methods
Study population: This research involved 30 healthy subjects
(males and females) and 90 patients who were diagnosed as
primary colorectal adenocarcinoma patients. The mean age
was 49.97 ±10.85 years for healthy subjects and 50.63±9.26
years for CRC patients. Healthy subjects matched the patients
in the gender ratio. Tumor lymph node metastasis (TNM)
system was used for staging. CRC patients were divided into
three equal groups; newly diagnosed (no treatment, no
surgery, all stages of disease), before surgery (chemo- and
radiotherapy-treated, stages III and IV), and after surgery (No
treatment before and after surgery, stages I and II). Patients
with diabetes, heart diseases, kidney failure, familial history
for CRC, intestinal polyposis, chronic digestive problems, and
those who are alcoholic and smokers were excluded. The
diagnosis for CRC patient was performed by consultant
doctors who identified tumor location, whereas tumor type,
grade, and stage were identified by pathologists. The ethics
committee of the Medical City in Baghdad, Iraq approved this
research. The number of CRC patients within stage I was 23
(25.55%), stage II was 23 (25.55%), stage III was 22
(24.44%), and stage IV was 22 (24.44%). The number of
patients with grade 1 was 22 (22.22%), grade 2 was 58 (64.44
%), and grade 3 was 12 (13.33%). Tumor location was
determined using the International Classification of Diseases
(ICD- version 10). Patients with colon and those with rectal
cancers were both included, where the number of patients who
had a primary tumor in the cecum was 4 (4.44%), in the
ascending colon,11 (12.22%), in the hepatic flexure,5
(5.55%), in the transverse colon, 8 (8.88%), in the splenic
flexure, 6 (6.66%), in the descending colon, 15 (16.66%), in
the sigmoid colon, 12 (13.33%), in the recto-sigmoid junction,
10 (11.11%), and in the rectum was 19 (21.11%).
Materials: Chemicals used for preparing standard solutions
of Zn, Cu and Se element were purchased from Merck KGaA,
Germany. Enzyme linked immunosorbent assay research kit
(type sandwich ELISA) was used to assay glutathione
peroxidase activity purchased from MyBioSource-U.S.A.
Laboratory assessment: Specimens were taken from healthy
subjects and CRC patients; Blood (10 mL) was collected from
each person, then the serum was stored at -40º C after being
separated by centrifugation. Atomic absorption spectroscopy
(AAS; novAA 300, Analytik Jena, Germany) was used to
assay Zn, Cu and Se, whereas flame atomic absorption
spectroscopy (FAAS) was used for Zn and Cu assay, using
acetylene–air as a flame and hollow cathode lamps as a

Caspian J Intern Med 2020; 11(4): 384-390
386 Al-ansari RF, et al.
radiation source. Burner height and gas flow rates were
adjusted to achieve the highest absorbance signal of each
element. Slit width used to isolate wavelength was 1 nm.
Absorbance was read at 213.9 nm and 324.7 nm, respectively,
for Zn and Cu. Hydride generation atomic absorption
spectroscopy (HGAAS) was used for Se assay. Hydride
generation system was heated to 950º C. Absorbance was read
at 196.0 nm. Carrier gas was argon. For hydride generation,
NaBH4 0.6% solution (98% Sigma, Germany) in 0.6% NaOH
(HiMedia Laboratories Pvt. Ltd., India) was prepared.
Samples were prepared by adding 3 mL of HNO3 70%
(HiMedia Laboratories Pvt. Ltd., India) to 1 mL of serum,
followed by decomposition by microwave according to a
specific program for decomposition. Samples were then left
for 10 min before adding deionized water to a defined volume.
These steps were applied to all samples. 5 mL of HCl 37%
(Sigma, Germany) was also added to samples prepared for the
Se assay which were heated at 85º C for 30 min (9).
Statistical analysis: IBM SPSS statistics Version 24 was used
to analyze the data by Windows 10. The parameters were
expressed as mean±SD, for normal distribution Shapiro- Wilk
test was used and for homogeneity of variance, Levene test
was used, One-way ANOVA test was used to find the
differences in the means between the groups also t-test. The
cutoff values and diagnostic markers were estimated by
receiving operating characteristic (ROC) curve. The Pearson
correlation coefficient was used to find the correlations among
the parameters. Differences at p<0.05 were considered to be
significant.
Results
The values of all the tested parameters (Zn, Cu, Se and
GPx) were significantly lower in all CRC patient groups as
compared to healthy subjects, except for the after surgery
group which showed no significant difference for Zn and GPx
table 1. Age (years) showed no differences between CRC
patient groups, newly diagnosed, before and after surgery,
(50.75±11.93, 52.00±12.79, and 49.16±12.08; respectively)
compared with healthy subjects (49.97±10.85). Body mass
index (Kg/m2) also showed no differences between CRC
patient groups (23.94±3.50, 24.18±4.55, and 24.02±4.03;
respectively) compared with healthy subjects (24.12±2.34).
The correlations among the parameters are shown in table 2,
while the positive correlations between Se and Zn and
between Se and GPx are shown in figures 1 and 2.
ROC curve analysis was applied for the newly diagnostic
group and showed that Zn, Cu, Se, and GPx can be used as
diagnostic markers for CRC disease; the area under the curve
(AUC) explains the ability of using these parameters as
markers. The analysis showed that all the differences in the
AUC values were significant (p<0.01). For each parameter,
95%-confidence interval (95%-CI) and standard error (SE) for
the AUC were calculated. The cutoff values were assessed at
the maximum of both sensitivity and specificity, as shown in
table 3.
Correlations between both BMI and age with the
parameters in healthy subjects and CRC patients are shown in
table 4. The associations of clinical features for CRC patients
and the parameters are shown in table 5.
Table 1. Total mean serum levels of Zn, Cu, and Se, with GPx activity in the sera of healthy subjects and CRC patients
Groups
Zn (μg/dL)
Mean±SD
Cu (μg/dL)
Mean±SD
Se (μg/dL)
Mean±SD
GPx (U/L)
Mean±SD
Healthy subjects
98.97±4.78
80.11±3.21
10.81±1.02
136.03±4.23
Newly diagnosed
69.37±3.72**
30.38±2.57**
2.87±0.56**
69.73±4.94**
Before surgery
78.43±5.01**
47.55±3.35**
4.77±1.06**
98.35±3.63**
After surgery
101.23±5.32
55.50±2.48*
7.44±1.21*
133.78±5.10
*P<0.05, **P<0.01
Table 2 .Correlations between parameters in serum for CRC patients
Correlation between
r (P-value)
Zn and Cu
-0.16 (>0.05)
Zn and Se
0.71 (<0.01)
Zn and GPx
0.24 (>0.05)
Cu and Se
0.01 (>0.05)
Cu and GPx
-0.07 (>0.05)
Se and GPx
0.42 (<0.01)

Caspian J Intern Med 2020; 11(4): 384-390
Trace elements and glutathione peroxidase in serum of colorectal cancer patients 387
Figure 1: Positive correlation between Se and Zn in
CRC patients.
Figure 2: Positive correlation between Se and GPx in
CRC patients.
Table 3. ROC curve analysis findings for parameters.
Parameters
AUC
SE
Sensitivity (%)
Specificity (%)
95% - CI
Cutoff value
Zn
0.91 *
0.04
89
69
0.82- 1.00
84.45 (μg/dL)
Cu
1.00 *
0.00
100
0
1.00- 1.00
55.24 (μg/dL)
Se
1.00 *
0.00
100
0
1.00- 1.00
5.40 (μg/dL)
GPx
0.91 *
0.05
78
84
0.80- 1.00
113.37 (U/L)
* P<0.01
Table 4. Correlations between both BMI and age with parameters in serum for healthy subjects and CRC patients
Correlation between
CRC Patients
r (p value)
Healthy subjects
r (P-value)
Zn and Age
0.03 (0.75)
-0.14 (0.53)
Cu and Age
-0.09 (0.43)
0.08 (0.73)
Se and Age
-0.005 (0.96)
0.18 (0.44)
GPx and Age
0.02 (0.87)
-0.29 (0.20)
Zn and BMI
-0.01 (0.93)
-0.22 (0.33)
Cu and BMI
-0.08 (0.50)
-0.03 (0.10)
Se and BMI
0.25 (0.04)
0.27 (0.26)
GPx and BMI
-0.01 (0.90)
0.04 (0.86)
Table 5. Association of clinical features for all CRC patients and serum levels of Zn, Cu, Se, and GPx
Group
Case (%)
Zn (μg/dL)
Mean±SD
Cu (μg/dL)
Mean±SD
Se (μg/dL)
Mean±SD
GPx (U/L)
Mean±SD
Sig.
Gender
Female
Male
48.88
51.11
82.77±2.32
83.23±1.34
45.91±1.86
43.02±3.69
4.99±0.4
5.03±0.5
98.98±3.56
102.22±4.43
N.S
Age
≤50
>50
52.22
47.77
81.87±5.04
84.13±4.43
45.70±3.76
43.22±2.34
5.03±0.6
4.99±0.3
99.37±3.56
101.95±2.43
N.S
Therapy*
Without
With
50.00
50.00
69.37±3.72
78.43±5.01
30.38±2.57
47.55±3.35
2.87±0.56
4.77±1.06
69.73±4.94
98.35±3.63
<0.001
*Only between two groups of CRC patients (the newly diagnosed and the before surgery). N.S: Non-significant

Caspian J Intern Med 2020; 11(4): 384-390
388 Al-ansari RF, et al.
Discussion
Alterations of trace element levels adversely affect many
biological processes and they could also promote
carcinogenesis. The results of our study showed that Zn, Cu,
Se and GPx were significantly lower in all groups of CRC
patients, while the patients in the after surgery group showed
no significant difference for both Zn and GPx, as shown in
table 1.
In the present study, all groups of CRC patients were
deficient in Cu and Se, as it was observed, for example, in the
newly diagnosed group in all stages as well as in the patients
before surgery who received radiotherapy and chemotherapy
in advanced stages. In the after surgery group, the early
surgical intervention in the patients with eral stage disease
could not restore normal levels of the studied elements, even
after 21 days of post-surgical blood collection. This indicates
that tumor removal was not efficient in bringing these
parameters to normal levels. A recent study on males and
female patients with thyroid cancer has demonstrated that
serum levels of Se significantly decreased in the pre- and post-
operative patients, an effect that was suggested to be
associated with thyroid cancer pathogenesis (19).
The rise in the levels of free radicals was related to cancer
etiology because such a rise can damage DNA, cause
destruction of proteins, and ultimately lead to tumor growth.
Copper-restricted diet in humans leads to elevated fecal free
radicals, and causes cytotoxicity which is one of the putative
colon cancer’s risk factors (20-23).
Moreover, experiments in animals indicated that low Cu
intake is considered as a risk factor for 3,2’-dimethyl-4-
aminobiphenyl (DMABP)-induced colon tumor development
in rats, whereas the activities of ceruloplasmin and Cu,Zn-
SOD enzymes were reduced in rats fed on low Cu intake (24).
Se is engaged in a number of biochemical pathways where it
can be found in many forms. Anticarcinogenic pathways of
Se include the prevention of oxidative damage, regulation of
immune responses, repair of DNA damage, and regulation of
apoptosis and cell cycle (25, 26). Selenomethionine is a major
component of Se diet that modulates the redox status
(reduction/oxidation) (20, 27). Besides that, it induces the
P53-mediated cell cycle arrest and programmed cell death in
human colon cancer cells (28). Se significantly induces
apoptosis and its relatively high doses were related to
overexpression of p53 in rat hepatocytes (29). A previous
study reported that low serum levels of Se were strongly
correlated with CRC risk (30). Zn level and GPx activity
significantly decreased in the newly diagnosed and before
surgery groups, but the levels showed non-significant
differences in the after surgery group as compared with
healthy subjects. This may be attributed to the stage and
differentiation grade of the disease. Our study with the after
surgery group involved patients in G1 and G2 grades only,
that showed non-significant difference in these parameters as
compared to the control group.
In a study conducted on colon and rectal cancer patients of
all stages of the disease who did not undergo surgical
intervention or treatment, the authors reported that the levels
of serum Zn significantly decreased but only in advanced
stages (31).
Another study in patients with colon and stomach cancer
demonstrated that high grade differentiated (G3; poorly
differentiated) stomach tissue has lower Zn level comparing
with the normal tissue and with the tissues from moderately
differentiated carcinoma G2 and well-differentiated
carcinoma G1 grades. Also, the study reported the inverse
association between Zn levels in the tissues and the advanced
stages of carcinoma in both colon and stomach cancer patients
(32). In our study, ROC curve analysis for the newly
diagnosed group was used to illustrate the association of these
parameters with CRC. The findings in table 3 indicate that the
parameters can be used as diagnostic markers, where a very
highly significant difference in AUC is shown. These values
can be used to predict people's health when the levels of these
parameters are less than the cutoff values, then the individuals
are at risk or already having CRC. A previous study noted that
the progression to colon cancer was associated with low levels
of Zn and decreased Cu,Zn-SOD activity in the plasma of rats
(33). P53 folding and misfolding is modulated by Zn, which
is one of the reasons that causes cancer (34). A previous study
about colorectal cancer showed that the serum levels of both
Zn and Cu were significantly lower as compared to healthy
people (13). Human CRC patients had lower serum
concentrations of Cu, Zn, and Se according to a review
published in 2019 (35). Our results are consistent with these
studies. Cu and Zn deficiencies have recently increased in
different regions of the world for unknown reasons. The total
prevalence of Cu deficiency in populations in Iran and Spain
was 32.1 % (age 15-65 years old) and 30.1 % (age over 60
years old), respectively. The Spanish study also reported that
the total prevalence of Zn deficiency was 66.8% (36, 37). The
positive correlation between Zn and Se that we found can be
explained by the results of a previous report which found that

Caspian J Intern Med 2020; 11(4): 384-390
Trace elements and glutathione peroxidase in serum of colorectal cancer patients 389
Zn can induce a decrease in Se urinary excretion (38). In a
previous study on humans, two significant positive
correlations between Zn and Se were found in two biological
media (urine and feces) from healthy people. The study also
found a significant positive correlation between dietary Zn
intake and Se levels in blood (39). Hence, Zn deficiency may
contribute to Se deficiency. Hypothetically, Zn may influence
the status of Se by modulating one of the phases of Se
homeostasis, represented by absorption, excretion or
retention. We also found another correlation between Se and
GPx, where Se deficiency led to decreased GPx activity,
which was previously shown to result in the accumulation of
H2O2, leading to destruction of the cells (14,5). In studies
conducted on colon cancer patients, the GPx activity was
reported to decrease in the plasma and serum (15, 16). Our
results have been consistent with these recent studies.
In our study, BMI was positively associated with serum Se
levels in CRC patients. A previous study found that high Se
diet causes a subclinical hypothyroid response which leads to
weight gain and decreases energy expenditure. But a low Se
diet causes a subclinical hyperthyroid response which leads to
weight loss and increases energy expenditure. Therefore,
dietary Se –intake alters the energy metabolism of humans
(40). Other parameters showed no association with BMI for
all CRC patients groups, including patients under treatment.
In a previous study on breast cancer, the patients showed a
BMI that was not affected by therapy (41).
In conclusions our findings indicate the involvement of
low levels of Zn, Cu, and Se as well as the low activity of GPx
in the pathogenicity of CRC. Zn level and GPx activity
significantly decreased in the newly diagnosed and before
surgery groups, but not in the after surgery group. This may
be attributed to the stage and differentiation grade of the
disease. Such low levels were not observed in the control
subjects, while the applied exclusion criteria could probably
exclude other possible sources of such declined levels, which
confirm the strict association between CRC and these
parameters. Thus, we conclude that Zn, Cu Se, and GPx can
be used as diagnostic markers for CRC, where the decrease of
these parameters may be associated with an increased risk of
CRC and as indicators of the response to therapy.
Acknowledgments
We thank the patients and healthy volunteers for their
support and participation in this research study and the staff
of the Medical City-Ministry of Health and Environment,
Baghdad, Iraq for their assistance.
Conflicts of interest: There are no conflicts of interest.
References
1. Torre LA, Bray F, Siegel RL, et al. Global cancer
statistics, 2012. CA Cancer J Clin 2015;65:87-108.
2. Fearon ER, Vogelstein B. A genetic model for colorectal
tumorigenesis. Cell 1990; 61: 759-67.
3. Ho E. Zinc deficiency, DNA damage and cancer risk. J
Nutr Biochem 2004; 15: 572-8.
4. Johnson MA, Fischer JG, Kays SE. Is copper an
antioxidant nutrient? Crit Rev Food Sci Nutr 1992; 32: 1-
31.
5. Pan YJ, Loo G. Effect of copper deficiency on oxidative
DNA damage in Jurkat T-lymphocytes. Free Radic Biol
Med 2000; 28: 824-30.
6. Collins JF, editor. Molecular, genetic, and nutritional
aspects of major and trace minerals. 1st ed. USA:
Academic Press 2016; pp: 449-61.
7. Kashyap D, Sharma A, Garg V, Singh Tuli H. Reactive
oxygen species (ROS): an activator of apoptosis and
autophagy in cancer. J Biol Chem Sci 2016; 3: 256-64.
8. Suleman M, Khan A, Baqi A, et al. Antioxidants, its role
in preventing free radicals and infectious diseases in
human body. Pure Appl Biol 2019; 8: 380-8.
9. Milde D, Altmannova K, Vyslouzil K, Stuzka V. Trace
element levels in blood serum and colon tissue in
colorectal cancer. Chem Pap 2005; 59: 157-60.
10. Al Faris NA, Ahmad D. Distribution of trace elements like
calcium, copper, iron and zinc in serum samples of colon
cancer A case control study. J King Saud Univ Sci 2011;
23: 337-40.
11. Al-Saadi NH, Al-Naqib MK, Ali ZH. Investigated of
ceruloplasmin activity and related elements, copper and
zinc in patients with colon cancer. Internat J Curr Eng
Technol 2014; 4: 2112-5.
12. Ribeiro SM, Moya AM, Braga CB, et al. Copper-Zinc
ratio and nutritional status in colorectal cancer patients
during the perioperative period. Acta Cir Bras 2016; 31:
24-8.
13. Khoshdel Z, Naghibalhossaini F, Abdollahi K, et al.
Serum copper and zinc levels among Iranian colorectal
cancer patients. Biol Trace Elem Res 2016;170:294-9.

Caspian J Intern Med 2020; 11(4): 384-390
390 Al-ansari RF, et al.
14. Margis R, Dunand C, Teixeira FK, Margis‐Pinheiro M.
Glutathione peroxidase family–an evolutionary overview.
FEBS J 2008; 275: 3959-70.
15. Ojo O. Glutothione peroxidase activities in leukemia, liver
and colon cancer patients. Global Sci J 2017; 5: 63-6.
16. Dusak A, Atasoy N, Demir H, et al. Investigation of levels
of oxidative stress and antioxidant enzymes in colon
cancers. J Clin Analyt Med 2017; 8: 469-73.
17. Ahuja N, Nettles BS, editors. Johns Hopkins patients'
guide to colon and rectal cancer, 1st ed. USA: The Johns
Hopkins University and the Johns Hopkins Health System
Corporation 2014; pp: 1-70.
18. Kuepper C, Grosserueschkamp F, Kallenbach-Thieltges
A, et al. Label-free classification of colon cancer grading
using infrared spectral histopathology. Faraday Discuss
2016; 187: 105-18.
19. Baltaci AK, Dundar TK, Aksoy F, Mogulkoc R. Changes
in the serum levels of trace elements before and after the
operation in thyroid cancer patients. Biol Trace Elem Res
2017; 175: 57-64.
20. Davies MJ. Protein oxidation and peroxidation. Biochem
J 2016; 473: 805-25.
21. Marnett LJ. Oxyradicals and DNA damage.
Carcinogenesis 2000; 21: 361-70.
22. Khanna R, Karki K, Pande D, Negi R, Khanna RS.
Inflammation, free radical damage, oxidative stress and
cancer. Microinflammation 2014; 1: 109.
23. Davis CD. Low dietary copper increases fecal free radical
production, fecal water alkaline phosphatase activity and
cytotoxicity in healthy men. J Nutr 2003; 133: 522-7.
24. Davis CD, Feng, Y. Dietary copper, manganese and iron
affect the formation of aberrant crypts in colon of rats
administered 3, 2′-dimethyl-4-aminobiphenyl. J Nutr
1999; 129: 1060-7.
25. Longtin R. Selenium for prevention: eating your way to
better DNA repair? J Natl Cancer Inst 2003; 95: 98-100.
26. Zeng H. Selenium as an essential micronutrient: roles in
cell cycle and apoptosis. Molecules 2009; 14: 1263-78.
27. Seo YR, Kelley MR, Smith ML. Selenomethionine
regulation of p53 by a ref1-dependent redox mechanism.
Proc Natl Acad Sci U S A 2002; 99: 14548-53.
28. Goel A, Fuerst F, Hotchkiss E, Boland CR.
Selenomethionine induces p53 mediated cell cycle arrest
and apoptosis in human colon cancer cells. Cancer Biol
Ther 2006; 5: 529-35.
29. Yu RA, Chen HJ, He LF, Chen B, Chen XM. Telomerase
activity and telomerase reverse transcriptase expression
induced by selenium in rat hepatocytes. Biomed Environ
Sci 2009; 22: 311-7.
30. Lener MR, Gupta S, Scott RJ, et al. Can selenium levels
act as a marker of colorectal cancer risk?. BMC Cancer
2013; 13: 214.
31. Gupta SK, Shukla VK, Vaidya MP, Roy SK, Gupta S.
Serum and tissue trace elements in colorectal cancer. J
Surg Oncol 1993; 52: 172-5.
32. Christudoss, P, Selvakumar R, Fleming JJ, Mathew G.
Zinc levels in paired normal and malignant human
stomach and colon tissue. Biomed Res 2010; 21:445-50.
33. Christudoss P, Selvakumar R, Pulimood AB, Fleming JJ,
Mathew G. Zinc and zinc related enzymes in precancerous
and cancerous tissue in the colon of dimethyl hydrazine
treated rats. Asian Pac J Cancer Prev 2012; 13: 487-92.
34. Loh SN. The missing zinc: p53 misfolding and cancer.
Metallomics 2010; 2: 442-9.
35. Nawi AM, Chin SF, Azhar Shah S, Jamal R. Tissue and
serum trace elements concentration among colorectal
patients: A systematic review of case-control studies. Iran
J Public Health 2019; 48: 632–43.
36. Parizadeh SMR, Kazemi-Bajestani SMR, Shapouri-
Moghaddam A, Ghayour-Mobarhan M, Esmaeili H,
Majdi MR, et al. Serum zinc and copper concentrations
and socioeconomic status in a large Persian cohort. Asian
Biomed 2011; 5: 329-35.
37. Olivares M, Lera L, Albala C, Pizarro F, Araya M.
Prevalence of zinc and copper deficiencies in older
subjects living in Metropolitan Santiago. Rev Med Chil
2011; 139: 283-9.
38. Chmielnicka J, Zareba G, Witasik M, Brzeźnicka E. Zinc-
selenium interaction in the rat. Biol Trace Elem Res 1988;
15: 267-76.
39. Wang Y, Ou YL, Liu YQ, et al. Correlations of trace
element levels in the diet, blood, urine, and feces in the
Chinese male. Biol Trace Elem Res 2012; 145: 127-35.
40. Hawkes WC, Keim NL. Dietary selenium intake
modulates thyroid hormone and energy metabolism in
men. J Nutr 2003; 133: 3443-8.
41. Ahmadi N, Mahjoub S, Haji Hosseini R, TaherKhani M,
Moslemi D. Alterations in serum levels of trace element in
patients with breast cancer before and after chemotherapy.
Caspian J Intern Med 2018; 9: 134-9.