Journal of Cancer Therapy, 2014, 5, 1-10
Published Online January 2014 (
GSTP1 (Ile105Val) Gene Polymorphism: Risk and
Treatment Response in Chronic Myeloid Leukemia
Shereen Elhosei ny1, Mohamed El-Wakil2, Mohamed Fawzy3, Aya Abdel Rahman1
1Department of Clinical and Chemical Pathology, Beni Suef Teaching Hospital, Beni Suef University, Beni Suef, Egypt; 2Depart-
ment of Clinical Oncology, Beni Suef Teaching Hospital, Beni Suef University, Beni Suef, Egypt; 3Department of Pediatric Oncolo-
gy, National Cancer Institute, Cairo University, Egypt.
Received November 14th, 2013; revised December 10th, 2013; accepted December 18th, 2013
Copyright © 2014 Shereen Elhoseiny et al. This is an open access article distributed under the Creative Commons Attribution Li-
cense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In
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Background: Genetic variation influencing individual susceptibility to chemical carcinogens is one of the main
factors leading to cancer development. The glutathione S-transferases (GSTs) are a family of enzymes belonging
to phase II enzymes involved in detoxification of xenobiotics. A significant relationship is observed between the
risk of developing cancer and genetic polymorphisms within GSTs. Methods: In this study, we investigated the
influence of inherited GSTP1 (Ile105Val) gene polymorphism on the susceptibility to CML in Egypt in 40 CML
patients (20 children and 20 adults), together with 40 healthy controls using a [PCR-RFLP] assay. Results: We
found that the mutant type (IIe/Val, Val/Val) was significantly higher in CML patients (67.5%) compared to
controls (35%) (p = 0.004); [odds ratio 3.9; 95% CI: 1.5 - 9.7]. The mutant type was associated with more ad-
vanced phases in disease and with both worse hematological and cytogenetic responses when compared to the
wild type (p = 0.03, p = 0.05, and p < 0.001, respectively). Conclusion: GSTP1 (Ile105Val) gene polymorphism
conferred a significant association with increased risk of CML and is associated with worse prognosis. Further
studies on the functional consequences of this genetic polymorphism would pave the way to declare its role in the
pathogenesis of CML or as a p oss ible predictor for resp ons e to ther apy.
CML; GSTs; GSTP1 (Ile105Val)
1. Introduction
Chronic myeloid leukemia (CML) is a clo nal myelopro-
liferative disease resulting from neoplastic transforma-
tion of multipotent stem cell. The disease is characterized
by high levels of leukocytes, splenomegaly, myeloid
hyperplasia in bone marrow and high levels of mature
myeloid cells in peripheral blood [1]. Although clinical
and biological aspects are well documented, little is
known about individual susceptibility to this disease [2].
Exposure to endogenous or exogenous toxic substances
can lead to genetic alterations and hence increased sus-
ceptibility to cancer [3]. It is claimed that cytotoxic and
genotoxic environmental agents (especially ionization,
radiation and similar factors) may increase the risk of
CML development [ 4]. Xenobiotic metabolizing en-
zymes (XMEs) constitute on e of the first lines of defense
against environmental chemicals. They play a central
role in the metabolism, elimination, and detoxification of
xenobiotics or exogenous compounds introduced into the
body [ 5]. Cells have developed an effective mechanism
to prevent accumulation of damaging xenobiotics by way
of their elimination catalyzed by multiple enzy me system.
The enzymes of the multiple enzyme system are classi-
fied in two categories namely Phase I and Phase II. Phase
I enzymes like Cytochrome P450 can activate the car-
cinogens directly and produce active metabolites while
Phase II enzymes like glutathione-S-transferase (GSTs)
can detoxify and process the activated metabolites for
final breakdow n [6].
GSTP1 (Ile105Val) Gene Polymorphism: Risk and Treatment Response in Chronic Myeloid Leukemia
The GSTs are a family of enzymes belonging to phase
II enzymes involved in detoxificati on of xe nobiotics (car-
cinogens, pesticides, antitumor agents & environmental
pollutants). Hence GSTs play a significant role in the
cellular defense. GSTs fall into two distinct super fami-
lies: membrane bound microsomal GSTs and the soluble
or cytosolic GSTs. The cytosolic glutathione S-tr an s-
ferase were classified into eight classes on the basis of
sequence diversity and designated as Alpha (α), Mu (μ),
Pi (л), Kappa (K), Theta (θ), Omega (O), Sigma (ε) and
Zeta (Z) [7]. These cytosolic enzymes play a major role
in the detoxification of a broad range of compounds, in-
cluding xenobiotics, pesticides, environmental carcino-
gens, PAH, and some chemotherapeutic drugs (including
alkylating agents, Doxorubicin, and Vincristein) [8]. Glu-
tathione S-transferase P1 (GSTP1) belongs to the pi class
gene family, located on chromosome 11q13 [9]. It spans
2.48 kb of DNA and comprises 7 exons that encode for
cytosolic GST enzyme. GSTP1 is considered as a major
antioxidant present in both the epidermis and the dermis,
overexpressed in a variety of preneoplastic and neoplas-
tic tissues [10]. In some cancer models, GSTP1 expres-
sion was considered as pre neoplastic tumor marker. In-
creased levels of GSTP1 in tumors might account for part
of the inherent drug resistance, which was observed in
many tumors suggesting its role in cancer etiology and
therapy [11].
GST polymorphisms may alter the ability of enzymes
to metabolize the chemical carcinogens and mutagens. It
had been suggested that these differences in the ability to
metabolize carcinogens and mutagens might influence
the susceptibility to cancer [4]. The first polymorphism
identified was an A-G polymorphism at nucleotide 313
in exon 5 of GST P1 gene which leads to an amino acid
substitution of isoleucine (IIe) by valine (Val) at 105
amino acid position (I le105Val). This substitution results
in three GSTP1 genotypes: they ar e isoleucine/isoleucine
(Ile/Ile) homozygous wild type, isoleucine/valine (Ile/Va l)
heterozygote and valine/valine (Val/Val) homozygous
variant. GSTP1 codon 105 polymorphism might play an
important role in leukemogenesis, as it potentially alters
protein function, diminishing its d etoxification ability f or
certain mutagens and carcinogens, which could result in
increased DNA damage and mutation, and a greater risk
of develo ping cance r [12].
To our knowledge, the GSTP1 (Ile105Val) gene has
never been studied in Egyptian CML patients. Thus, this
study was done to investigate the influence of inherited
genetic polymorphism of GSTP1 (Ile105Val) on the sus-
ceptibility to CML in Egyptian pediatric and adult pa-
tients evaluating its impact on the response to therapy.
2. Patients and Methods
Included pediatric and adult patients underwent cross
sectional evaluation as regards study parameters while
forty unrelated healthy individuals were served as control
In the present study 40 Egyptian CML patients were
included; 20 children and 20 adults at different phases of
disease; newly diagnosed or received treatment. Patients
were recruited from the Pediatric Oncology Department,
National Cancer Institute (NCI), Cairo University and
from Beni Suef University Hospital. Data confidentiality
was preserved according to the Revised Helsinki De-
claration of Bioethics (2008) [13].
Patients were subjected to full history taking and tho-
rough clinical examination. In addition, laboratory in-
vestigations as complete blood count (CBC), liver and
kidney functions, serum uric acid, LDH and coagulation
profile were reviewed. Diagnosis of CML was based on
morphologic findings from Giemsa stained smears of
peripheral blood sample, cytochemical stains criteria
such as LAP score, Philadelphia chromosome detection
by conventional cytogenetic study and BCR ABL fusion
gene detected by FISH.
Treatment and phase of disease:
Medical records of all patients were reviewed as re-
gards clinical data, diagnostic laboratory information,
treatment received, and disease status. Patients in chronic
phase (CML-CP) received debulking hydroxyurea and
imatinib (STI571/Glivec) tyrosine kinase inhibitor (TKI)
at 340 mg/m2/day in children and 400 mg/day for adults.
One pediatric patient in chronic phase underwent allo-
geneic bone marrow transplantation (BMT). Patients
progressed to myeloid blastic crisis within the course of
their therapy were candidates for AML-like treatment.
Children received ADE (Ara-c, Daunorubicin, Etoposide)
as induction therapy followed by postremission consoli-
dation in form of MidAC (Mitoxantrone, Ara-c). Adult
patient was candidate for high dose ara-c based regimens.
Adults in acceleration phase received escalated imatinib
dose of 600 - 800 mg daily [14,15].
Patients were evaluated according to hematologic and
cytogenetic response where
Complete hematological response (CHR) was de-
fined as a WBC count <10 × 109/L, a platelet count
<450 × 109/L, basophils <5%, no immature cells
(blasts, promyelocytes, myelocytes) in the peripheral
blood, and disappearance of all signs and symptoms
related to leukemia.
Cytogenetic response was expressed in terms of the
ratio of number of Ph+ metaphases in bone marrow
divided by initial number of Ph+ metaphases and ca-
tegorized as follows:
1) Complete response: 0% Ph+ cells; 2) Partial re-
sponse: 1% - 35% Ph+ cells, 3) Minor response: 36% -
GSTP1 (Ile105Val) Gene Polymorphism: Risk and Treatment Response in Chronic Myeloid Leukemia
65% Ph+ cells, 4) Minimal response: 66% - 95% Ph+
cells, and 5) No response: more than 95% Ph+ cells [16].
DNA isolation and GSTP1 (Ile105Val) polymor-
genotype analysis:
Mononuclear cells (MNCs) were isolated from 2 ml
peripheral blood or BM aspirate at diagnosis by Ficoll
density gradient centrifugation. Genomic DNA was ex-
tracted using Gene JET Genomic DNA purification kit
(Cat. #K0721, #KO722, Fermentas Life Sciences) accor-
ding to the manufacturers instructions.
GSTP1 (Ile105Val) polymorphism was determined
with a polymerase chain reaction-restriction fragment
length polymorphism assay [PCR-RFLP]. The PCR pri-
mers were: 5’-GTA GTT TGC CCA AGG TCA AG-3’
(F) and 5’-AGC CAC CTG AG G GGT AAG-3’ (R) [17].
PCR assay was performed for each sample in a final
reaction volume of 25 µL, using 5 µL genomic DNA,
12.5 µL universal master mix, 1 µL forward primer, 1 µL
reverse primer, together with 5.5 µL distilled water (DW).
The PCR conditions w ere as follows: Initial denaturation
at 95˚C for 12 min. followed by 15 cycles of: denatura-
tion at 95˚C for 30 sec, annealing at 58˚C for 30 sec and
extension at 72˚C for 60 sec. Followed by 25 cycles of
amplification: denaturation at 95˚C for 30 sec, annealing
at 55˚C for 30 sec and extension at72˚C for 60 se c. Then
one cycle of final extension step at 72˚C for 5 min [18].
All reactions were done using the thermal cycler App lied
Biosystems (Perkin Elmer 9600).
The PCR product was digested with the restriction
endonuclease Alw26I restriction enzyme [16] (Fer-
mentas, Fast Digest ® Alw26I # FD0034) and put at
37˚C for 30 minutes. The products were then resolved on
2% agarose gel electrophoresis containing ethidium bro-
mide, then visualized using UV transilluminator. DNA
molecular weight marker (QIAGEN GelPilot 50 bp Lad-
der (100) {ca t no. 239 025} was used to assess the size of
the PCR-RFLP products.
The amplified fragment after digestion with Alw26I
restriction enzyme, gave rise to: 2 fragments at 329 bp
and 107 bp indicating the presence of wild type (IIe/IIe),
app earan ce of 2 fragments at 222 bp and 107 bp indicates
the presence of homozygous mutant type (Val/Val),
while presence of 3 fragments at329 bp, 222 bp and 107
bp indicates the presence of heterozygous mutant type
(Ile/Val) (Figure 1). For quality control, genotyping of
10 % of the samples was repeated and interpreted blindly
by two different observers and proved to be identical to
the initial results.
Statistical Methods:
Data was analyzed using IBM SPSS advanced statis-
tics version 20 (SPSS Inc., Chicago, IL). Numerical data
of scores were expressed as mean and standard deviation
or median and range as appropriate. Qualitative data
were expressed as frequency and percentage. Chi-square
test (Fisher’s exact test) was used to examine the relation
between qualitative variables. For quantitative data,
comparison between two groups was done using Mann-
Whitney test (non parametric t-test). Comparison be-
tween 3 groups was done using Kruskal-Wallis test (non-
parametric ANOVA) then post-Hoc “Schefe test” on
rank of variables was used for pair-wise comparison.
Survival analysis was done using Kaplan-Meier method
Figure 1. PCR-R FLP analysis of GSTP1 (Ile105Val) gene polymorphism using Alw26I restriction enzyme: M: DNA molecular
weight marker: 50 - 500 bp Lane 2, 6, 8, 10: Homozygous wild type (Ile/Ile): 2 bands at 329 and 107 bp Lane 1, 3, 7: Hetero-
zygous mutant (Ile/Val): 3 bands 329, 222 & 107 bp Lane 4, 5, 9, 11: Homozygous mutant (Val/Val): 2 bands at 222, 107 bp.
GSTP1 (Ile105Val) Gene Polymorphism: Risk and Treatment Response in Chronic Myeloid Leukemia
and comparison between two survival curves was done
using log-rank test. Odds ratio (OR) with it 95% confi-
dence interval (CI) were used for risk estimation. A
p-value < 0.05 was considered significant [19].
3. Results
Comparisons between the 2 patients groups was carried
out and shown in Table 1. The only statistically signifi-
cant difference between pediatric and adult groups was in
the TLC showing lower values in adults compared to
childhood CML patients (p = 0.03).
Results of GSTP1 (Ile105Val) gene polymorphism
among all study patients are shown in Table 2. The mu-
tant types (IIe/Val, and Val/Val) were more frequently
represented in CML patients compared to controls (Fig-
ure 2).
UMutant gene types in childhood CML patients:U The
mutant types (IIe/Val and Val/Val) were more frequent
Table 1. Clinical parameters, hematological parameters, and outcome of CML patients.
p Adulthood patients (n = 20) Childhood patients (n = 20) Parameter
12 (60%) 12 (60%)
8 (40%) 8 (40%)
Fema l e s
46.1 ± 11.3 (27 - 67) 12.9 ± 3.2 (7 - 18)
Age at diagnosis (yrs)
0.03 88.8 ± 83.6 (25 - 353) 160.4 ± 110.8 (17 - 394)
Total leucocytic count (×109/L)
0.4 9.5 ± 2 (5.9 - 14.8) 8.9 ± 1.4 (6.6 - 11.7)
Hemoglobin (gm/dl)
0.1 371.6 ± 286 (110 - 1120) 240.9 ± 232.6 (12 - 920)
Platelets (×109/L)
0.7 1.8 ± 5.3 (0 - 23) 4.8 ± 9.8 (0 - 27)
Peripheral blood blasts (%)
0.1 65.8 ± 55.77 (10 - 110) 56.6 ± 71.28 (7 - 120)
LAP score
20/20 (100%) 20/20 (100%)
0.9 18/20 (90%) 19/20 (95%)
Philadelphia chromosome + ve
Table 2. Frequency of GSTP1 (Ile105Val) genotypes among childhood patients, adulthood patients, combined CML patients,
and controls.
p-value Odds ratio 95%
Children CML
patients (n = 20) Adults CML
patients (n = 20) Com bined CML
patients (n = 40) Controls
(n = 40)
No (%) No (%) No (%) No (%)
Wild genotype IIe/IIe 6 (30%) 7 (35%) 13 (32.5%) 26 (65%) Reference
Heterozygous IIe/Val 10 (50%) 9 (45%) 19 (47.5%) 12 (30%)
0.03a 3.6a 1.1 - 12.3a
0.09b 2.8b 0.8 - 9.3b
0.02c 3.2c 1.2 - 8.5c
Homozygous Val/Val 4 (20%) 4 (20%) 8 (20%) 2 (5.0%)
0.02d 8.7d 1.3 - 58.8d
0.03e 7.4e 1.1 - 49.2e
0.01f 8.0f 1.5 - 43.2f
All mutants
(IIe/Val + Val/Val) 14 (70%) 13 (65%) 27 (67.5%) 14 (35%)
0.01g 4.3g 1.4 - 13.8g
0.02h 3.4h ͪ 1.1 - 10.6h
0.004i 3.9i 1.5 - 9.7i
Comparison between: heterozygous mutant IIe/Val genotype versus wild IIe/IIe genotype among achildhood, badulthood, or ccombined CML patients versus
controls; homozygous mutant Val/Val genotype versus wild IIe/IIe genotype among dchildhood, eadulthood, or fcombined CML patients versus controls; all
mutant (IIe/Val + Val/Val) genotypes versus wild IIe/IIe genotype among gchildhood, ha dultho od, or icombined CML patients versus controls.
GSTP1 (Ile105Val) Gene Polymorphism: Risk and Treatment Response in Chronic Myeloid Leukemia
Figure 2. GSTP1 (Ile105Val) gene polymorphism in childhood CML patients, adulthood CML patients and control groups.
among childhood CML patients (70%) compared to con-
trols (35%), (p = 0.01). Calculated odds ratio revealed
fourfold increased risk of CML with mutant types. The
homozygous mutant type (Val/Val) was 20% in CML
pediatric patients compared to only 5% among controls
(p = 0.02), with calculated odds ratio revealed eightfold
increased risk of CML. On the other hand, the heterozy-
gous mutant type (IIe/Val) found in 50% of pediatric
patients compared to 30% in controls (p = 0.03) with
calculated odds ratio revealed almost fourfold increased
risk of CML (Table 2 an d Figure 2).
Mutant gene types in adulthood CML patients:
Table 2
mutant types (IIe/Val and Val/Val) were more frequent
among adult CML patients (65%) compared to controls
(35%), (p = 0.02). Calculated odds ratio revealed more
than threefold increased risk of CML. The homozygous
mutant type (Val/Val) like in childhood group, was 20%
in CML patients compared to only 5% in controls (p =
0.03), and calculated odds ratio revealed more than se-
venfold increased risk of CML. As for the heterozygous
mutant type (IIe/Val), although it was more frequently
represented among patients (45%) compared to 30% in
controls, yet the difference was not of statistical signi-
ficance (p = 0.09). However, calculated odds ratio re-
vealed almost threefold increased risk of CML for hete-
rozygous mutants ( and Figure 2).
Characteristics and outcome of childhood (Table 3 )
and adulthood (Table 4) CML patients as regards
GSTP1 (Ile105Val) gene polymorphism: In patients
with CML-CP, mutant gene types wer e found in 11/16 of
children (68.8%) versus 58.8% in adults. Among other
phases of disease, 3/4 (75%) of childhood patients had
blastic crisis during their treatment course found to be
harboring the mutant type, compared to only 1/4 (25%)
harboring the wild type. Another 2 adulthood patients
with accelerated phase of disease were harboring the
mutant type (100%) as well, whereas the only adult pa-
tient with blastic crisis was harboring the mutant type
GSTP1 (Ile105Val) gene polymorphism pattern in
different CML Phases and its impact on response
among combined study patients (Table 5): Among all
study patients of different age groups there was a sta-
tistically significant difference between the wild gene
type IIe/IIe and mutant types (IIe/Val or Val/Val) as re-
gards CML phases. Both accelerated phase and blastic
crisis were more common in patients harboring the mu-
tant type (57.1% homozygous mutant, 28.6% heterozy-
gous mutant, and only 14.3% with wild type; p = 0.03).
The mutant type was associated with poorer hematolo-
gical response as all p atients who didnt achieve CHR (n
= 6) were harboring the mutant type; 3 homozygous, and
3 heterozygous mutants (p = 0.05).
Again, the mutant type was also associated with poorer
cytogenetic response. While 9/9 patients (100%) with
minimal cytogenetic response had the mutant type; the
homozygous mutant gene found in 6/9 (66.7%) was more
com mo n in comparison to heterozygous mutant gene
pattern found in 3/9 (33.3%) of those patients. On the
other hand, complete cytogenetic response was more in
patients harboring the wild type (75%) compared to the
heterozygous (25%), and homozygous (0%) mutant types,
(p < 0.001).
Allele frequency among combined study patients
versus controls (Table 6 and Figure 3): The Val allele
was significantly higher in CML patients (43.7%) when
results of all patients were compared collectively to con-
trols (20% ) (p = 0.001).
GSTP1 (Ile105Val) Gene Polymorphism: Risk and Treatment Response in Chronic Myeloid Leukemia
Table 3. Patients characteristics and outcome in 20 Childhood CML patients in relation to GSTP1 (Ile105Val) polymorphism.
p Mutant genes (n = 14) (IIe/Val + Val/Val) Wild gene (n = 6) (IIe/IIe) Parameter
9 (75%) 3 (50%)
Gender: males: No (%)
5 (62.5%) 3 (50%)
Females: No (%)
0.9 12.8 ± 3 (8 - 17)* 13 ± 3.8 (7 - 18)*
Age at diagnosis (yrs)
0.7 167.9 ± 116.6 (63 - 394)* 142.8 ± 103.9 (17 - 250)*
Total leucocytic count (× 109/L)
0.5 9.0 ± 1.4 (7.7 - 11.7)* 8.7 ± 1.7 (6.6 - 11.1)*
Hemoglobin (gm/dl)
0.9 249.5 ± 259.5 (12 - 920)* 220.8 ± 172.8 (71 - 550)*
Platelets (× 109/L)
0.6 52.5 ± 70.72 (7 - 120)* 66 ± 78.4 (10 - 110)*
LAP score
14/20 (70%) 6/20 (30%)
Splenomegaly (n = 20)
0.08 14/19 (73.7%) 5/19 (26.3%)
Philadelphia chromosome + ve (n = 19)
11/16 (68.8%)
Phase of CML
5/16 (31.2%)
Chronic (n = 16)
- -
Accelerated (n = 0)
3/4 (75%) 1/4 (25%)
Blastic Crisis (n = 4)
10/16 (62.5%)
Hematological response
6/16 (37.5%)
Complete (n = 16)
4 (100%) -
Less than complete (n = 4)
UCytogenetic Response
1/5 (20%) 4/5 (80%)
Complete (n = 5)
9/11 (81.8%) 2/11 (18.2%)
Partial (n = 11)
4/4 (100%) -
Minimal (n = 4)
*Mean ± SD (range), **No p value because of small no of cases within subgroups.
Figure 3. GSTP1 (Ile105Val) alleles among childhood CML, adult CML patients and control groups.
GSTP1 (Ile105Val) Gene Polymorphism: Risk and Treatment Response in Chronic Myeloid Leukemia
Table 4. Patients characteristics and outcome in 20 adulthood CML patients in relation to GSTP1 (Ile105Val) polymorphism.
p Mutant genes (n = 13) (IIe/Val + Val/Val) Wild gene (n = 7) (IIe/IIe) Parameter
8 (66.7%) 4 (33.3%)
Gender: Males: No (%)
5 (62.5%) 3 (37.5%)
Females: No (%)
0.1 43.5 ± 10.5 (27 - 66)* 51 ± 11.9 (31 - 67)*
Age at diagnosis (yrs)
0.2 104 ± 97.4 (37 - 353)* 60.4 ± 41.1 (25 - 126)*
Total leucocytic count (×109/L)
0.8 9.4 ± 2.3 (5.9 - 14.8)* 9.5 ± 1.6 (7.7 - 12)*
Hemoglobin (gm/dl)
0.5 363.6 ± 316 (110 - 1120)* 386.3 ± 242.7 (150 - 774)*
Platelets (×109/L)
0.1 77.85 ± 57.88 (13 - 110)* 43.43 ± 47.46 (10 - 101)*
LAP score
13/20 (65%) 7/20 (35%)
Splenomegaly (n = 20)
0.09 13/18 (72.2%) 5/18 (27.8%)
Philadelphia chromosome + ve (n = 18)
10/17 (58.8%)
Phase of CML
7/17 (41.2%)
Chronic (n = 17)
2/2 (100%) -
Accelerated (n = 2)
1/1 (100%) -
Blastic Crisis (n = 1)
11/18 (61.1%)
Hematological response
7/18 (38.9%)
Complete (n = 18)
2/2 (100%) -
Less than complete (n = 2)
UCytogenetic response
2/7 (28.6%) 5/7 (71.4%)
Complete (n = 7)
6/8 (75%) 2/8 (25%)
Partial (n = 8)
5/5 (100%) -
Minimal (n = 5)
*Mean ± SD (range), **No p value because of small no of cases within subgroups.
Table 5. Impact of GSTP1 (Ile105Val) gene polymorphism on CML Phases and outcome in all 40 (combined) CML patients.
p value
Mutant types n = 27/40 (67.5%)
Wild type (IIe/IIe)
n = 13/40 (32.5%)
Parameter Homozygous (Val/Val) 8/27 (20%) Heterozygous (IIe/Val) 19/27 (47.5%)
No (%) No (%) No (%)
UPhase of CML:
4/33 (12.1%) 17/33 (51.5%) 12/33 (36.4%)
Chronic (n = 33)
Accelerated + blastic
4/7 (57.1%) 2/7 (28.6%) 1/7 (14.3%)
crisis (n = 7)
UHematological response
5 (14.7%) 16 (47.1%) 13 (38.2%)
Complete (n = 34)
3 (50%) 3 (50%) 0 (0%)
Less than complete (n = 6)
< 0.001
UCytogenetic response
- 3 (25%) 9 (75%)
Complete (n = 12)
2/19 (10.5%) 13/19 (68.4%) 4/19 (21.1%)
Partial (n = 19)
6/9 (66.7%) 3/9 (33.3%) -
Minimal (n = 9)
GSTP1 (Ile105Val) Gene Polymorphism: Risk and Treatment Response in Chronic Myeloid Leukemia
Table 6. Allele frequency in different CML patients and controls.
(95% confidence interval) Odds ratio p value
GSTP1 allele
Group Val Allele Ile Allele
20% 80%
Controls (n = 40)
1.428 - 7.502a 3.273a 45% 0.004a 55%
Childhood CML patients (n = 20)
1.286 - 6.797b 2.957b 42.5% 0.009b 57.5%
Adulthood CML patients (n = 20)
1.539c - 6.288c 3.111c 43.7% 0.001c 56.3%
Combined CML patients (n = 40)
0.373 - 2.186d 0.903d 0.8d
Childhood versus adulthood CML patients
Allele frequency among aChildhood, bAdulthood or, cAll (combined) CML patients versus controls. dAllele frequency among childhood CML versus adult
4. Discussion
CML is a myeloproliferative disorder but definite me-
chanism leading to this carcinogenesis is not completely
understood ye t [6]. Genetic susceptibility studies of CML
may serve to identify populations at risk and clarify im-
portant disease mechanisms. Genetic variants within
genes that encode enzymes involved with metabolism
such as GST have been shown to increase the likelihood
of developing various forms of cancers [20]. An associa-
tion between the polymorphic forms of the XMEs and
the altered risk to various cancers including CML was
reported [3]. Several studies investigated the relationship
between GST polymorphisms and acute leukemia [12,21].
However, there is very little information on the role of
GST polymorphisms in CML development. To the best
of our knowledge, Taspinar et al. 2008, studied the
GSTM1 and GSTT1 polymorphisms [4], while in two
other studies GSTP1 (Ile105Val) gene polymorphism
was studied in CML patients [17, 22].
In the current study, frequency of the mutant gene
types (IIe/Val and Val/Val) was significantly higher in
CML patients compared to controls (respectively 67.5%
v 35%; p = 0.004), with fourfold increased risk of CML.
This is in accordance with some other investigators re-
ported that there was an association between the GSTP1
(Ile105Val) polymorphism and the occurrence of CML
[17]. On contrary, Karkucah et al. 2012 didnt find any
statistically significant difference between CML patients
and the control group as regards the GSTP1 (Ile105Val)
gene polymorphism [22].
It was also reported that heterozygote mutant type Ile/
Val was elevated in a group of patients below 20 years
when compared to patients in higher age groups. This
agrees with our findings as the heterozygous mutant type
was 50% in childhood compared to 45% in adulthood
patients. Authors suggested that the presence of valine
allele confers increased risk to develop CML at early age.
This was attributed to the reduced rate of detoxification
of metabolites derived due to UVR-derived oxidative
stress and other environmental carcinogens. We also
found that the homozygous mutant type (Val/Val) was
significantly higher in our CML patients (20%) com-
pared to controls (5%). This was in agreement to same
investigators data but at different frequencies as homo-
zygous mutant type was significantly elevated among
their study patients compared to controls (6.5% v 1.2%,
respectively) [17].
In previous studies, individuals with at least one Val
allele at codon 105 of GSTP1 enzyme were thought to
have an underlying predisposition to cancer when ex-
posed to environmentally derived or endogenously for-
med GSTP1 substrates [23]. Indeed, the GSTP1 codon
105Val allele was associated with a significantly in-
creased risk of lung, bladder, testicular cancer, cancer
breast, and multiple myeloma [23-26]. Valin e genotype
has decreased enzyme activity which might be due to
altered catalytic activity and thermal stability of the en-
zyme. This could lead to less detoxifying efficiency for
the ultimate carcinogens like polycyclic aromatic hydro-
carbons (PAH) which can induce DNA adducts and ul-
timately lead to carcinogenesis [27]. The Val allele was
significantly higher in CML patients compared to con-
trols in our study which similarly found by other’s data
[16]. In discrepancy, the Val allele was higher in controls
compared to CML patients in another study, yet it was of
no statistically significant difference [22].
According to our results, CML patients in advanced
phases (acceleration/blastic crisis) had higher frequency
of mutant gene types. Homozygous mutant was higher
(57.1%) than the heterozygous one (28.6%) and they
were both higher than wild type (14.3%). These findings
could be explained according to other studies suggesting
that valine allele predispose the individuals to develop
advance d di sease [17].
When response to treatment was considered, the mu-
tant type was associated with poorer hematological re-
sponse. All 6 patients who didnt achieve complete re-
mission were harboring the mutant type (50% homozyg-
ous and 50% heterozygous). On the contrary, Sailaja et al.
GSTP1 (Ile105Val) Gene Polymorphism: Risk and Treatment Response in Chronic Myeloid Leukemia
2010 did not find any association between hematological
response and GSTP1 polymorphism. However, as re-
gards cytogenetic response, the frequency of combined
genotypes (Ile/Val and Val/Val) was elevated in patients
with minor cytogenetic response compared to major res-
ponders which is in agreement to our data [17]. These
results had suggested that GSTP1 Ile105Val polymor-
phism with reduced GSTP1 enzyme activity might result
in accumulation of intermediate metabolites in the body
leading to additional mutations which might influence
disease progression and response rates.
Yet, the limitation of our study was small sample size
and lack of sufficient information about the environmen-
tal factors which limited the analysis of the interaction
between the genetic and environmental factors. Therefore,
these results must be verified by further studies with
larger patient populations as well as larger control popu-
5. Conclusion
In conclusion, this is the first report highlighting the ge-
netic susceptibility due to GSTP1 (Ile105Val) polymer-
phism and the risk of CML in the Egyptian patients. The
current study revealed that GSTP1 (Ile105Val) polymer-
phism might contribute to the risk of CML development.
The mutant genotype is linked to poor treatment response
and worse prognosis. So, better understanding of the
functional consequences of GSTP1 (Ile105Val) gene po-
lymorphism would provide a basis for future studies of
the role of this polymorphism in the pathogenesis of
CML. It can also be used in predicting clinical outcome
and prognosis in CML patients.
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