Radiol Oncol 2021; 55(2): 179-186. doi: 10.2478/raon-2021-0002
179
research article
The role of polymorphisms in glutathione-
related genes in asbestos-related diseases
Alenka Franko
1,2
, Katja Goricar
3
, Metoda Dodic Fikfak
1,2
, Viljem Kovac
2,4
, Vita Dolzan
3
1 
Clinical Institute of Occupational Medicine, University Medical Centre Ljubljana, Ljubljana, Slovenia
2 
Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
3  
Pharmacogenetics Laboratory, Institute of Biochemistry and Molecular Genetics, Faculty of Medicine, University of 
Ljubljana, Ljubljana, Slovenia
4 
Institute of Oncology Ljubljana, Ljubljana, Slovenia
Radiol Oncol 2021; 55(2): 179-186.
Received 9 November 2020 
Accepted 2 December 2020
Correspondence to: Prof. Vita Dolžan, M.D., Ph.D., Pharmacogenetics Laboratory, Institute of Biochemistry and Molecular Genetics,  
Faculty of Medicine, University of Ljubljana, Vrazov trg 2, SI-1000 Ljubljana, Slovenia; Phone +386 1 543 76 70; GSM: +386 51 625 455;  
Fax: + 386 1 543 76 41; E-mail: vita.dolzan@mf.uni-lj.si
Disclosure: No potential conflicts of interest were disclosed. 
Background. The study investigated the influence of GCLC, GCLM, GSTM1, GSTT1 and GSTP1 polymorphisms, as 
well as the influence of interactions between polymorphism and interactions between polymorphisms and asbestos 
exposure, on the risk of developing pleural plaques, asbestosis and malignant mesothelioma (MM).
Subjects and methods. The cross sectional study included 940 asbestos-exposed subjects, among them 390 sub-
jects with pleural plaques, 147 subjects with asbestosis, 225 subjects with MM and 178 subjects with no asbestos-related 
disease. GCLC rs17883901, GCLM rs41303970, GSTM1 null, GSTT1 null, GSTP1 rs1695 and GSTP1 rs1138272 genotypes 
were determined using PCR based methods. In statistical analysis, logistic regression was used.
Results. GSTT1 null genotype was associated with the decreased risk for pleural plaques (OR = 0.63; 95% CI = 0.40–
0.98; p = 0.026) and asbestosis (OR = 0.51; 95% CI = 0.28–0.93; p = 0.028), but not for MM. A positive association was 
found between GSTP1 rs1695 AG + GG vs. AA genotypes for MM when compared to pleural plaques (OR = 1.39; 95% 
CI = 1.00–1.94; p = 0.049). The interactions between different polymorphisms showed no significant influence on the risk 
of investigated asbestos-related diseases. The interaction between GSTT1 null polymorphism and asbestos exposure 
decreased the MM risk (OR = 0.17; 95% CI = 0.03–0.85; p = 0.031). 
Conclusions. Our findings suggest that GSTT1 null genotype may be associated with a decreased risk for pleural 
plaques and asbestosis, may modify the association between asbestos exposure and MM and may consequently act 
protectively on MM risk. This study also revealed a protective effect of the interaction between GSTP1 rs1695 polymor-
phism and asbestos exposure on MM risk. 
Key words: polymorphisms; glutathione-related genes; asbestos; asbestosis; pleural plaques; malignant mesothelioma
Introduction
Asbestos exposure, which still represents an im-
portant health problem worldwide, is known to 
be associated with the development of asbestos-
related diseases, including benign pleural diseases 
(e.g. pleural plaques), asbestosis, lung cancer, ma-
lignant mesothelioma (MM) and other types of 
cancer.
1,2
 The pathogenesis of asbestos-related dis-
eases is complicated and not entirely elucidated. 
Nevertheless, numerous studies have suggested 
that in addition to a direct mechanical injury, as-
bestos may stimulate the production of reactive 
oxygen and nitric species (ROS and RNS) that were 
shown to have an important role in the pathogen-
esis of these diseases. ROS and RNS may cause 

Radiol Oncol 2021; 55(2): 179-186.
Franko A et al. / Glutathione-related polymorphisms in asbestos diseases 180
asbestos-related lung injury, DNA strand breaks 
in mesothelial cells and may increase the risk for 
developing malignancy.
3-5
 
To detoxify ROS and consequently prevent the 
adverse effects of oxidative stress, the human or-
ganism possesses antioxidant defence systems. 
Glutathione (GSH), a tripeptide composed from 
glutamic acid, cysteine and glycine, is an abundant 
cellular antioxidant which has a major role in the 
protection against oxidative injury in cells. It serves 
as a substrate of many antioxidative enzymes.
6,7
 
The antioxidant capacity of the glutathione system 
depends on enzymes involved in its biosynthe-
sis, such as glutamate cysteine ligase (GCL), also 
known as gamma glutamylcysteine synthetase, 
as well as on detoxification enzymes, such as glu-
tathione S-transferases (GSTs).
6,8-10
GCL is the rate limiting enzyme of the GSH 
synthesis and it is suggested to be the major fac-
tor that determines GSH level in healthy subjects. 
The enzyme consists of two subunits: a heavy cata-
lytic subunit (GCLC) and a light modifier subunit 
(GCLM).
6,10
 High GSH concentration levels found 
in many tumors have been associated with the in-
creased GCL activity.
11,12
GSTs are phase II detoxifying enzymes in-
volved in the inactivation of the electrophiles 
produced by ROS and RNS by catalyzing the 
conjugation of electrophilic compounds with re-
duced glutathione.
8,9
 In mammals, seven classes of 
cytosolic GST isoenzymes have been recognized: 
Alpha, Mu, Pi, Sigma, Theta, Omega and Zeta.
13
 
The crucial GST enzyme in the human lung, which 
belongs to the Pi class, is GSTP1.
14,15
 Two other im-
portant polymorphic GSTs are GSTM1 (Mu class) 
and GSTT1 (Theta class).
15,16
 
Genes coding for GSH related enzymes are 
polymorphic. Among the most commonly investi-
gated promoter polymorphisms of the GCLC and 
GCLM genes are GCLC rs17883901 (c.-129C>T) and 
GCLM rs41303970 (c.-590 C>T).
17-20
 Some studies 
indicated that polymorphisms in GCLC and GCLM 
genes are associated with low levels of reduced 
GSH in vitro, which may explain susceptibility to 
certain diseases related to oxidative stress.
17,18
 The 
GCLC rs17883901 polymorphism has been suggest-
ed to suppress the GCLC gene induction response 
to oxidants and it has been implicated in coronary 
endothelial dysfunction and myocardial infarc-
tion.
17
 GCLC rs17883901 has also been proposed to 
modulate the renal disease risk in type 1 diabetes 
patients.
21
 The presence of GCLC rs17883901 T al-
lele and GCLM rs41303970 T allele has also been 
associated with an increased risk of ischemic heart 
disease.
19
 However, according to the available lit-
erature the association between GCLC and GCLM 
polymorphisms and asbestos-related diseases has 
not been studied so far.
Regarding GSTM1 and GSTT1 genes, the most 
common polymorphism is due to homozygous 
deletion of these genes (null genotype), which 
results in the lack of the GSTM1 and GSTT1 en-
zyme activity.
22,23
 In the GSTP1 gene, two common 
single nucleotide polymorphisms (SNPs) have been 
described that lead to amino acid substitution and 
consequently reduced enzyme conjugating activ-
ity: GSTP1 rs1138272 (p.Ala114Val) and GSTP1 
rs1138272 (p.Ala114Val).
22
 Hirvonen et al. reported 
an increased risk for developing MM for indi-
viduals with GSTM1 null genotype.
24
 Similarly, 
Landi et al. found an increased risk for MM in 
subject with GSTM1 null allele, while no effect 
was observed for GSTP1 and GSTT1 polymor-
phisms.
25
 In the study of Kukkonen et al., GSTT1 
null genotype increased the risk for asbestos-related 
severe fibrotic changes and GSTM1 null geno-
type was associated with the greatest thickness of 
the pleural plaques.
26
 Our former study showed 
that asbestosis was associated with GSTT1 null 
genotype, but not with GSTM1 null genotype.
27
 
Furthermore, we have reported the influence of 
GSTP1 rs1695 on the asbestosis risk, while no 
association was found between GSTP1 rs1138272 
and asbestosis risk.
28
The present study aimed to investigate the influ-
ence of GCLC, GCLM, GSTM1, GSTT1 and GSTP1 
polymorphisms on the risk for developing pleural 
plaques, asbestosis and MM. In addition, we also 
investigated the influence of gene-gene interac-
tions and interactions between glutathione-related 
polymorphisms and asbestos exposure on the risk 
for developing these diseases. 
Subjects and methods
Study population
The cross sectional study included all together 940 
asbestos-exposed subjects, among them 390 sub-
jects with pleural plaques, 147 subjects with asbes-
tosis, 225 subjects with MM and 178 subjects with 
no asbestos-related disease. Subjects with pleural 
plaques, asbestosis and MM were considered as 
cases, and those with no asbestos-related disease 
as controls. 
Additionally, comparison was made between 
subjects with MM and subjects with pleural 
plaques.

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Franko A et al. / Glutathione-related polymorphisms in asbestos diseases 181
Subjects with pleural plaques, asbestosis and 
subjects with no asbestos-related disease were 
presented at the State Board for the Recognition 
of Occupational Asbestos Diseases in the period 
from 1 January 1998 to 31 December 2007 and were 
all occupationally exposed to asbestos. The infor-
mation on all the subjects included was revised 
in 2018 to verify the latest diagnoses of asbestos-
related diseases. Subjects with MM were recruited 
at the Institute of Oncology Ljubljana, where they 
were treated in the period between 1 February 2004 
and 31 December 2018. The study was approved 
by the Slovenian Ethics Committee for Research 
in Medicine and was carried out according to the 
Declaration of Helsinki. 
Clinical diagnosis
The diagnosis of pleural plaques, asbestosis or 
“no asbestos-related disease” was verified by 
two groups of experts of the State Board for the 
Recognition of Occupational Asbestos Diseases, 
each group consisting of a specialist of occupa-
tional medicine, a pulmonologist, and a radiolo-
gist. Subjects with pleural MM were diagnosed 
by ultrasound-guided biopsy or thoracoscopy and 
those with peritoneal MM by laparoscopy. The di-
agnosis of MM was proved histopathologically by 
a pathologist experienced in diagnosing this malig-
nant disease. 
Smoking and asbestos exposure 
Data on smoking were collected during an inter-
view based on a standardized questionnaire. The 
number of pack-years of smoking was calculated 
from the duration of smoking and the number of 
cigarettes smoked per day. 
Data on cumulative asbestos exposure in fibres/
cm
3
-years were available for the subjects with pleu-
ral plaques, asbestosis, “no asbestos-related dis-
ease” and for 28 patients with MM. Based on the 
data on cumulative asbestos exposure, the asbestos 
exposures in these subjects were divided into three 
groups: low (< 11 fibres/cm
3
-years), medium (11–20 
fibres/cm
3
-years) and high (> 20 fibres/cm
3
-years) 
asbestos exposure. For the subjects with MM who 
lacked the data on cumulative asbestos exposure, 
asbestos exposures were assessed based on the pre-
cise work history and comparison with exposures 
of the group of subjects with known cumulative 
asbestos exposure. Accordingly, their asbestos ex-
posures were divided into three groups with pre-
sumed low, medium or high asbestos exposure.
DNA extraction and genotyping
Genomic DNA was extracted from peripheral 
blood samples using Qiagen FlexiGene Kit (Qiagen, 
Hilden, Germany) according to the manufacturer’s 
instructions.
GSTP1 rs1695, GSTP1 rs1138272, GCLC rs17883901, 
and GCLM rs41303970 genotypes were determined 
using competitive allele-specific polymerase chain 
reaction (KASP) assays (LGC Genomics, UK) follow-
ing the manufacturer’s instructions. Homozygous 
GSTM1 and GSTT1 gene deletions (null genotype) 
were determined using multiplex PCR in a single re-
action as previously described with HBB gene serv-
ing as a positive control.
29
Statistical methods
Standard descriptive statistics was used to describe 
central tendency and variability of investigated 
variables. Chi-square test and Kruskal-Wallis test 
were used to compare categorical and continu-
ous variables among different groups, respective-
ly. Deviation from Hardy-Weinberg equilibrium 
(HWE) was also evaluated using chi-square test. 
Dominant and additive genetic models were used 
in the analysis. To compare genotype frequencies 
among groups, univariable and multivariable lo-
gistic regression models were used and odds ratios 
(ORs) with 95% confidence intervals (CIs) were cal-
culated. Characteristics used for adjustment in mul-
tivariable analysis were selected using stepwise for-
ward-conditional logistic regression. The possible 
interactions between genotypes as well as between 
genetic polymorphisms, and between genetic poly-
morphisms and asbestos exposure were tested by 
logistic regression models using dummy variables.
Statistical analysis was carried out with IBM 
SPSS Statistics version 21.0 (IBM Corporation, 
Armonk, NY, USA). All statistical tests were two-
sided and the level of significance was set at 0.05.
Results
The characteristics of the groups of subjects with 
pleural plaques, asbestosis, MM and subjects 
without asbestos-related disease are presented in 
Table 1. A statistically significant difference be-
tween the groups was observed for the age (p < 
0.001), pack-years of smoking (p = 0.024) and as-
bestos exposure (p < 0.001). The mean age was the 
highest for subjects with MM (65 ± 10.7 years), fol-
lowed by subjects with asbestosis (58.7 ± 9.1 years). 

Radiol Oncol 2021; 55(2): 179-186.
Franko A et al. / Glutathione-related polymorphisms in asbestos diseases 182
The mean values of pack-years of smoking were 
the highest in subjects with asbestosis (24.4 ± 18.6) 
and in subjects with MM (23.2 ± 17.2). Regarding 
asbestos exposure, the percent of subjects with low 
asbestos exposure was the highest for the group of 
subject with no asbestos-related disease (77.5%), 
followed by the group of subjects with pleural 
plaques (72.3%) (Table 1).
The genotype frequencies for all studied genetic 
polymorphisms are shown in Table 2. Genotype 
frequencies for all investigated SNPs were con-
cordant with HWE.
TABLE 1. Characteristics of subjects without asbestos-related disease, subjects with pleural plaques, asbestosis or malignant mesothelioma
Characteristic
No disease
(N = 178)
Pleural plaques
(N = 390)
Asbestosis
(N = 147)
Malignant 
mesothelioma 
(N = 225)
P
Gender
Male, N (%) 119 (66.9) 277 (71.0) 110 (74.8) 164 (72.9) 0.407
Chi-square = 2.905, 
df = 3 Female, N (%) 59 (33.1) 113 (29.0) 37 (25.2) 61 (27.1)
Age (years)
Mean ± SD 57.6 ± 9.5 55.8 ± 9.5 58.7 ± 9.1 65.0 ± 10.7
< 0.001
Test-statistic = 115.390
Median (25%–75%) 56.6 (49.6–65.1) 55.0 (48.8–62.7) 59.1 (51.4–65.3) 66 (58–73)
Min–max 38.2–79.9 34.4–85.8 37.2–79.2 19–95
Smoking 
No, N (%) 95 (53.4) 193 (49.5) 72 (49.0) 117 (53.7) [7] 1.614
Chi-square = 0.656, 
df = 3 Yes, N (%) 83 (46.6) 197 (50.5) 75 (51.0) 101 (46.3)
Pack-years of smoking 
(smokers only)
Mean ± SD 21.0 ± 15.8 [4] 18.1 ± 15.6 [22] 24.4 ± 18.6 [2] 23.2 ± 17.2 [14]
0.024
Test-statistic = 9.474
Median (25%–75%) 20 (9–30) 15 (5–28) 22.8 (10–32.7) 20 (8–35)
Min–max 0.1–65.3 0.05–96.6 0.15–90 1–69
Asbestos exposure
Low, N (%) 138 (77.5) 277 (72.3) [7] 75 (51.7) [2] 34 (45.9) [151]
< 0.001
Chi-square = 53.864, 
df = 6
Middle, N (%) 13 (7.3) 38 (9.9) 28 (19.3) 23 (31.1)
High, N (%) 27 (15.2) 68 (17.8) 42 (29.0) 17 (23.0)
Number of missing data is presented in [] brackets. P-values were calculated using chi-square test for categorical or Kruskal-Wallis test for continuous variables. SD = standard 
deviation
TABLE 2. Genotype frequencies in all subjects, subjects without asbestos-related disease, subjects with pleural plaques, asbestosis and malignant 
mesothelioma
Polymorphism Genotype
All subjects
(N = 940)
No disease
(N = 178)
Pleural plaques
(N = 416)
Asbestosis
(N = 160)
Malignant 
mesothelioma  
(N = 154)
GCLC rs17883901
c.-129C>T
CC 772 (82.1) 149 (83.7) 310 (79.5) 124 (84.4) 189 (84)
CT 162 (17.2) 29 (16.3) 78 (20) 23 (15.6) 32 (14.2)
TT 6 (0.6) 0 (0) 2 (0.5) 0 (0) 4 (1.8)
GCLM rs41303970
c.-590C>T
CC 581 (61.8) 114 (64) 233 (59.7) 87 (59.2) 147 (65.3)
CT 306 (32.6) 54 (30.3) 135 (34.6) 51 (34.7) 66 (29.3)
TT 53 (5.6) 10 (5.6) 22 (5.6) 9 (6.1) 12 (5.3)
GSTM1 Gene deletion
present 384 (40.9) 74 (41.6) 159 (40.8) 64 (43.5) 87 (38.7)
null genotype 556 (59.1) 104 (58.4) 231 (59.2) 83 (56.5) 138 (61.3)
GSTT1 Gene deletion
present 782 (83.2) 138 (77.5) 330 (84.6) 128 (87.1) 186 (82.7)
null genotype 158 (16.8) 40 (22.5) 60 (15.4) 19 (12.9) 39 (17.3)
GSTP1 rs1695
p.Ile105Val
AA 454 (78.3) 78 (43.8) 202 (51.8) 76 (51.7) 98 (43.6)
AG 394 (41.9) 81 (45.5) 155 (39.7) 55 (37.4) 103 (45.8)
GG 92 (9.8) 19 (10.7) 33 (8.5) 16 (10.9) 24 (10.7)
GSTP1 rs1138272
p.Ala114Val
CC 785 (83.5) 141 (79.2) 334 (85.6) 121 (82.3) 189 (84)
CT 146 (15.5) 34 (19.1) 54 (13.8) 23 (15.6) 35 (15.6)
TT 9 (1.0) 3 (1.7) 2 (0.5) 3 (2) 1 (0.4)

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Franko A et al. / Glutathione-related polymorphisms in asbestos diseases 183
In univariate logistic regression analysis, no 
association was found between GCLC rs17883901 
and GCLM rs41303970 genetic polymorphisms and 
asbestos-related diseases.
GSTT1 null genotype was associated with the 
decreased risk for asbestos-related diseases when 
analysed together (OR = 0.63; 95% CI = 0.42–0.95; p 
= 0.026). When analysing the risk for each disease 
separately, GSTT1 null genotype was associated 
with the decreased risk for pleural plaques (OR 
= 0.63; 95% CI = 0.40–0.98; p = 0.026) and asbesto-
sis (OR = 0.51; 95% CI = 0.28–0.93; p = 0.028), but 
not for MM. No association was found between 
GSTM1 null genotype and asbestos-related dis-
eases. Regarding GSTP1 polymorphisms, a posi-
tive association was found between GSTP1 rs1695 
AG + GG vs. AA genotypes for MM only when 
compared to pleural plaques (OR = 1.39; 95% CI = 
1.00–1.94; p = 0.049) (Table 3).
Regarding age, no association was found be-
tween age and pleural plaques (OR = 0.98; 95% CI 
= 0.96–1.00; p = 0.032). A slight association was ob-
served between age and MM (OR = 1.07; 95% CI = 
1.05–1.10; p < 0.001), as well as between age and 
MM when compared to pleural plaques (OR = 1.10; 
95% CI = 1.08–1.12; p < 0.001).
The analysis of association between asbestos 
exposure and asbestos-related diseases revealed 
a positive association between high and medium 
vs. low asbestos exposure and all asbestos-related 
diseases (OR = 1.93; 95 % CI = 1.31–2.85; p = 0.001), 
between high and medium vs. low asbestos expo-
sure and asbestosis (OR = 3.22; 95% CI = 1.99–5.20; 
p < 0.001), and between high and medium vs. low 
asbestos exposure and MM (OR = 4.06; 95% CI = 
2.28–7.23; p < 0.001). When analysing the associa-
tion between high and medium vs. low asbestos ex-
posure and MM compared to pleural plaques, the 
OR was 3.07 (95 % CI = 1.85–5.12; p < 0.001).
In multivariate logistic regression analysis, 
the risk of GSTT1 null genotype for all asbestos-
related diseases together (OR = 0.62; 95% CI = 
0.41–0.94; p = 0.025) and separately for asbestosis 
(OR = 0.51; 95% CI = 0.27–0.95; p = 0.033) did not 
change considerably after adjustment for asbestos 
exposure. Similarly, the risk of GSTT1 null geno-
type for pleural plaques remained practically un-
changed after adjustment for age (OR = 0.63; 95% 
CI = 0.40–0.99; p = 0.046). On the contrary, the 
risk of GSTP1 rs1695 AG + GG vs. AA genotypes 
for MM compared to pleural plaques increased 
slightly (OR = 1.97; 95% CI = 1.14–3.39; p = 0.015) 
TABLE 3. The association between different asbestos-related diseases and genotypes in univariate analysis
Polymorphism Genotype
Asbestos-related disease 
vs. no disease
Pleural plaques  
vs. no disease
Asbestosis  
vs. no disease
MM  
vs. no disease
MM  
vs. plaques
OR (95% CI) P OR (95% CI) P OR (95% CI) P OR (95% CI) P OR (95% CI) P
GCLC 
rs17883901
CC Reference Reference Reference Reference Reference
CT+TT 1.15 (0.74–1.78) 0.541 1.33 (0.83–2.12) 0.237 0.95 (0.52–1.73) 0.874 0.98 (0.57–1.67) 0.937 0.74 (0.48–1.14) 0.169
GCLM 
rs41303970
CC Reference Reference Reference Reference Reference
CT 1.14 (0.80–1.63) 0.476 1.22 (0.83–1.80) 0.308 1.24 (0.77–1.99) 0.378 0.95 (0.61–1.46) 0.809 0.77 (0.54–1.11) 0.164
TT 1.05 (0.51–2.15) 0.895 1.08 (0.49–2.35) 0.853 1.18 (0.46–3.03) 0.732 0.93 (0.39–2.23) 0.872 0.86 (0.42–1.80) 0.697
CT+TT 1.13 (0.80–1.58) 0.495 1.20 (0.83–1.73) 0.330 1.23 (0.78–1.93) 0.369 0.95 (0.63–1.43) 0.788 0.79 (0.56–1.11) 0.170
GSTM1
present Reference Reference Reference Reference Reference
null 
genotype
1.04 (0.74–1.44) 0.828 1.03 (0.72–1.48) 0.857 0.92 (0.59–1.44) 0.721 1.13 (0.76–1.69) 0.554 1.09 (0.78–1.53) 0.608
GSTT1
present Reference Reference Reference Reference Reference
null 
genotype
0.63 (0.42–0.95) 0.026 0.63 (0.40–0.98) 0.041 0.51 (0.28–0.93) 0.028 0.72 (0.44–1.18) 0.198 1.15 (0.74–1.79) 0.527
GSTP1 rs1695
AA Reference Reference Reference Reference Reference
AG 0.80 (0.57–1.13) 0.209 0.74 (0.51–1.07) 0.114 0.70 (0.44–1.11) 0.129 1.01 (0.67–1.53) 0.955 1.37 (0.97–1.94) 0.075
GG 0.80 (0.45–1.40) 0.428 0.67 (0.36–1.25) 0.208 0.86 (0.41–1.80) 0.698 1.01 (0.51–1.97) 0.988 1.50 (0.84–2.67) 0.170
AG+GG 0.80 (0.58–1.11) 0.185 0.73 (0.51–1.04) 0.078 0.73 (0.47–1.13) 0.157 1.01 (0.68–1.5) 0.958 1.39 (1.00–1.94) 0.049
GSTP1 
rs1138272
CC Reference Reference Reference Reference Reference
CT+TT 0.70 (0.46–1.05) 0.087 0.64 (0.40–1.01) 0.056 0.82 (0.47–1.43) 0.482 0.73 (0.44–1.21) 0.216 1.14 (0.72–1.79) 0.583
Statistically significant results are printed in bold. MM = malignant mesothelioma

Radiol Oncol 2021; 55(2): 179-186.
Franko A et al. / Glutathione-related polymorphisms in asbestos diseases 184
after adjustment for asbestos exposure and age 
(Table 4).
In further logistic regression analysis, the inter-
actions between polymorphisms showed no signif-
icant influence on the risk for developing asbestos-
related diseases (data not shown). 
Testing the influence of interactions between 
asbestos high and medium vs. low exposure and 
genetic polymorphisms on the risk of asbestos-re-
lated diseases, the interaction between asbestos ex-
posure and GSTT1 null polymorphism decreased 
the risk for developing MM (OR = 0.17; 95% CI = 
0.03-0.85; p = 0.031). Similarly, the interaction be-
tween asbestos exposure and GSTT1 null polymor-
phism (OR = 0.11; 95% CI = 0.02–0.49; p = 0.004) 
and the interaction between asbestos exposure and 
GSTP1 rs1695 polymorphism (OR = 0.14; 95% CI 
= 0.03–0.65; p = 0.012) decreased the risk of MM 
when compared to pleural plaques.
Discussion
The present study investigated the influence of 
genetic polymorphisms in GSH related genes, the 
interactions between these polymorphism, and in-
teractions between polymorphisms and asbestos 
exposure on the risk of asbestos-related diseases.
The present study revealed a protective effect 
of GSTT1 null genotype on the risk of all studied 
asbestos-related diseases together and particu-
larly on the risk of pleural plaques and asbestosis. 
The explanation of these findings could be that in 
some instances GSTT1 may catalyse toxification 
and not detoxification reaction, leading to even 
more reactive conjugate.
15
 This observation is in 
agreement with the results of our previous study, 
in which GSTT1 null genotype also decreased the 
asbestosis risk.
27
 On the other hand, in the present 
study GSTM1 null genotype showed no effect on 
the risk of asbestos-related diseases, which is also 
consistent with the results of our previous study.
27
 
Similar findings were observed by Jakobsson et 
al., who reported no association between GSTM1 
deficiency and parenchymal and pleural abnor-
malities among the workers exposed to asbestos
30
, 
and also by Hirvonen et al., who revealed no in-
creased risk for the asbestos-related pulmonary 
disorders in subjects with homozygous deletion of 
GSTM1 gene.
16
 Contrary to the results of our study, 
TABLE 4. The association between different asbestos-related diseases and genotypes in multivariate analysis
Polymorphism Genotype
Asbestos-related disease 
vs. no disease
Pleural plaques  
vs. no disease
Asbestosis  
vs. no disease
MM  
vs. no disease
MM  
vs. plaques
OR (95% CI) P OR (95% CI) P OR (95% CI) P OR (95% CI) P OR (95% CI) P
GCLC 
rs17883901
CC Reference Reference Reference Reference Reference
CT+TT 1.18 (0.75–1.86) 0.466 1.33 (0.83–2.12) 0.240 0.96 (0.52–1.78) 0.893 0.66 (0.28–1.57) 0.344 0.57 (0.26–1.23) 0.154
GCLM 
rs41303970
CC Reference Reference Reference Reference Reference
CT 1.16 (0.8–1.68) 0.431 1.22 (0.82–1.79) 0.323 1.10 (0.67–1.81) 0.695 0.98 (0.51–1.87) 0.945 0.76 (0.43–1.36) 0.360
TT 1.16 (0.55–2.42) 0.696 1.06 (0.48–2.32) 0.883 1.37 (0.52–3.63) 0.524 1.13 (0.33–3.84) 0.844 1.05 (0.35–3.09) 0.934
CT+TT 1.16 (0.82–1.64) 0.406 1.19 (0.82–1.72) 0.351 1.14 (0.72–1.83) 0.576 1.00 (0.55–1.84) 0.994 0.80 (0.47–1.38) 0.429
GSTM1
present Reference Reference Reference Reference Reference
null 
genotype
1.04 (0.74–1.46) 0.837 1.06 (0.74–1.53) 0.738 0.84 (0.53–1.34) 0.464 1.09 (0.60–1.98) 0.774 1.09 (0.63–1.87) 0.756
GSTT1
present Reference Reference Reference Reference Reference
null 
genotype
0.62 (0.41–0.94) 0.025 0.63 (0.4–0.99) 0.046 0.51 (0.27–0.95) 0.033 1.00 (0.48–2.08) 0.996 1.28 (0.65–2.53) 0.479
GSTP1 rs1695
AA Reference Reference Reference Reference Reference
AG 0.78 (0.54–1.11) 0.162 0.74 (0.51–1.07) 0.113 0.65 (0.40–1.06) 0.087 1.23 (0.66–2.32) 0.513 1.86 (1.04–3.30) 0.036
GG 0.8 (0.45–1.43) 0.461 0.67 (0.36–1.24) 0.203 0.96 (0.45–2.06) 0.920 1.65 (0.65–4.16) 0.288 2.40 (1.04–5.54) 0.039
AG+GG 0.78 (0.56–1.1) 0.153 0.72 (0.51–1.04) 0.077 0.71 (0.45–1.12) 0.140 1.31 (0.72–2.39) 0.370 1.97 (1.14–3.39) 0.015
GSTP1 
rs1138272
CC Reference Reference Reference Reference Reference
CT+TT 0.68 (0.44–1.04) 0.078 0.64 (0.4–1.02) 0.059 0.84 (0.47–1.51) 0.565 0.73 (0.34–1.60) 0.433 1.02 (0.49–2.13) 0.965
MM = malignant mesothelioma. Statistically significant results are printed in bold. 
Adjustments made: Asbestos-related disease vs. no disease, Asbestosis vs. no disease: adjusted for asbestos exposure; Pleural plaques vs. no disease: adjusted for age; MM vs. 
no disease, MM vs. plaques: adjusted for asbestos exposure, age

Radiol Oncol 2021; 55(2): 179-186.
Franko A et al. / Glutathione-related polymorphisms in asbestos diseases 185
Kukkonen et al. reported that GSTT1 null genotype 
increased the risk of asbestosis and GSTM1 null 
genotype was related to the greatest thickness of 
the pleural plaques.
26
 Although Landi et al. ob-
served an increased risk for MM in subjects bear-
ing GSTM1 null allele
25
, in our current study, no 
association was found between either GSTM1 null 
genotype or GSTT1 null genotype and MM risk.
The results of our study showed that GSTP1 
rs1695 AG + GG vs. AA genotypes increased the 
MM risk, while GSTP1 rs1138272 polymorphism 
did not affect the risk of this malignoma. On the 
contrary, GSTP1 polymorphisms did not influence 
the MM risk in the study by Landi et al.
25
Our study revealed no influence of GCLC 
rs17883901 and GCLM rs41303970 on the risk for 
asbestos-related diseases. Our results suggest that 
these two polymorphisms are not related to the 
susceptibility to asbestos-related diseases. To our 
knowledge, no other studies investigated the role 
of polymorphic genes involved in GSH synthesis 
in asbestos-related diseases. 
Our study confirmed the impact of high and 
medium vs. low asbestos exposure on the risk for 
asbestosis and MM, which is consistent with the 
findings of previous studies.
31-34
 However, our re-
sults also showed that nearly 46% of subjects with 
MM, 52% of subjects with asbestosis and 72% sub-
jects with pleural plaques had low asbestos expo-
sure. This suggests that asbestos-related diseases 
can also develop when asbestos exposures are low, 
which was indicated especially for MM.
35,36
 
In this study, the interactions between investi-
gated GSH related gene polymorphisms did not 
influence the risk for developing asbestos-related 
diseases. On the other hand, we observed that the 
interaction between GSTT1 null polymorphism 
and asbestos exposure decreased the risk for devel-
oping MM, although there was no independent as-
sociation between GSTT1 null and MM when com-
pared to controls with no asbestos-related disease. 
In other words, GSTT1 null genotype modified the 
association between high and medium vs. low as-
bestos exposure and MM and acted protectively on 
the risk of this malignant disease.
Another interesting finding of this study showed 
that the interaction between GSTP1 rs1695 AG + 
GG vs. AA genotypes and asbestos exposure de-
creased the risk of MM when compared to pleural 
plaques, despite the fact that in univariate analysis 
both GSTP1 polymorphism and asbestos exposure 
were associated with an increased risk of MM. 
The relation between benign pleural plaques and 
the risk of MM has not been clearly proved so far. 
Although pleural plaques may be the endpoint and 
the development of pleural plaques may be an en-
tirely independent process from the development 
of MM
37
, it is likely that there is a relation between 
pleural plaques and MM.
38
 The present study sug-
gests a modifying and protective effect of GSTP1 
rs1695 genotypes on the association between as-
bestos exposure and MM risk when compared to 
pleural plaques.
Considering the potential limitations of the 
study, the data on asbestos exposure were not 
available for all subjects, especially not for patients 
with MM. Consequently, the analyses of the inter-
actions between genetic polymorphisms and as-
bestos exposure could be performed only for the 
subgroup of MM patients.
On the other hand, the study also brings nov-
el findings and has some important strengths. 
Firstly, according to our knowledge, this is the 
first study to investigate the association between 
GCLC rs17883901 and GCLM rs41303970 genetic 
polymorphisms and asbestos-related diseases. 
Secondly, it included relatively large numbers of 
subjects with different asbestos-related diseases 
from genetically homogenous population and in-
vestigated functional genetic polymorphisms in 
different GSH related genes.
In conclusion, our findings suggest that among 
genetic polymorphisms in GSH related genes, 
GSTT1 null polymorphism may be associated with 
the risk for developing pleural plaques and asbes-
tosis and may also modify the association between 
asbestos exposure and MM and therefore act pro-
tectively on the risk for this malignoma. This study 
also revealed a modifying and protective effect of 
GSTP1 rs1695 polymorphism on the association be-
tween asbestos exposure and MM risk when pleu-
ral plaques were considered as controls.
Acknowledgements and funding
The authors would like to thank Savica Soldat, 
Urška Slapšak, Ana Cirnski and Maj Bavec for their 
help with genotyping analyses. This work was fi-
nancially supported by the Slovenian Research 
Agency (ARRS Grants Nos. P1-0170, L3-8203 and 
L3-2622).
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