GLUT-1 Expression in Breast Cancer
Oguzhan OKCU1, Bayram SEN2, Cigdem OZTURK1, Gulname FINDIK GUVENDI1, Recep BEDIR1
1Department of Pathology, Recep Tayyip Erdoğan University Training and Research Hospital, RIZE, TURKEY
2Department of Biochemistry, Recep Tayyip Erdoğan University Training and Research Hospital, RIZE, TURKEY
Keywords: Breast cancer, Immunohistochemistry, GLUT-1
Numerous studies have been conducted to predict the prognosis of breast cancers. The effect of glucose transporter protein 1
(GLUT-1), the main carrier protein responsible for glucose transport, was investigated in breast cancer patients.
Material and Method: 170 patients operated for breast carcinoma were included in this study. We analysed the prognostic significance of
GLUT-1 immune-expression in 149 patients without neoadjuvant therapy, and in 21 patients with neoadjuvant therapy.
Results: GLUT-1 expression was correlated with poor prognostic factors such as estrogen receptor and progesterone receptor negativity, high
Ki-67 proliferation index, and high histological and nuclear grade (p<0.001). GLUT-1 was expressed at a statistically higher rate in invasive ductal
carcinomas, compared to invasive lobular carcinomas (p <0.001), and was expressed at a higher rate in luminal B, human epidermal growth
factor receptor 2 and triple-negative molecular subtypes compared to luminal A subtype tumors (p <0.001). There was no statistically significant
difference between GLUT-1 expression and presence of neoadjuvant therapy. Univariate survival analysis showed high GLUT1 expression was
associated with low disease-free survival.
Conclusion: GLUT-1 expression was found to be associated with poor pathological prognostic factors in breast carcinoma patients. The
results suggest that GLUT-1 expression can be considered as a prognostic marker in breast cancers, and it may be used as a target molecule in
personalized treatment approaches.
According to the Globocon 2018 data, breast cancers are
the most common cancer in 11 regions worldwide and the
first cause of cancer-related deaths in women. Around 2
million new patients and 600,000 deaths were recorded
worldwide in 2018 1
The most important prognostic factors used in the
treatment planning of patients are the TNM staging system
and hormone receptor expression profiles 2. A very
different prognosis is observed among patients of a similar
stage. Therefore, different markers remain the subject of
research to identify patients with poor prognosis and to
develop new individualized treatment modalities.
Glucose transporter protein 1 (GLUT-1) is the main carrier
protein responsible for physiological and pathological
glucose transport. The expression of GLUT-1 increases
with the effect of hypoxia and decreased oxidative
phosphorylation to meet the increasing energy need of
tumor cells for proliferation, invasion, and metastasis 3-5.
In our study, we aimed to determine the prognostic
significance of GLUT-1 expression in breast cancer patients, the relationship between GLUT-1 expression
level and clinicopathological prognostic parameters, and
the effect of neoadjuvant therapy on GLUT-1 expression.
|Study Design and Case Selection
Patients treated with invasive breast carcinoma with
mastectomy +/- axillary lymph node materials operated
in our center between January 2017 and April 2020
were retrospectively scanned from the departmental
databases. Paraffin blocks, hematoxylin-eosin slides, and
immunohistochemical slides (estrogen receptor (ER),
progesterone receptor (PR), human epidermal growth
factor receptor 2 (HER 2), Ki-67) were retrieved from the
pathology archives. Patients whose materials could not be
found, and whose clinical data could not be reached were
excluded from the study. A total of 170 female patients
were included in the study.
Mastectomy + axillary lymph node dissection was
performed in 154 patients, and simple mastectomy in
16 patients. Neoadjuvant chemotherapy treatment was
applied in 21 of the patients.
Two different study groups were formed according to
neoadjuvant treatments. The prognostic significance
of GLUT-1 expression and its relationship with
clinicopathological parameters were evaluated in the
main study group of 149 patients who did not receive
neoadjuvant therapy. The effect of neoadjuvant therapy
on GLUT-1 expression was evaluated in the second study
group consisting of 21 patients who received neoadjuvant
Slides stained with Hematoxylin-eosin and with
immunohistochemical markers for ER (SP1, Ventana), PR
(1E2, Ventana), HER2 (4B5, Ventana), and Ki-67 (30-9,
Ventana) were re-evaluated and re-scored by 2 pathologists
(O.O., Ç.Ö.). For each case, a paraffin block containing
sufficient tumor area was determined to apply GLUT-1
Gender, age, survival time, development of metastasis, and
data of recurrence were obtained from the hospital and
national electronic databases. In addition, pathological
data such as tumor diameter, pathological stage, nuclear
grade, histological grade, axillary lymph node metastasis
were obtained from the pathology reports.
Disease-free survival is defined as the time to clinical, radiological,
or pathological metastasis/recurrence after major
surgery or the time to the last follow-up. Unfortunately, we
could not analyze overall survival due to the short followup
Histopathological and Immunohistochemical Staining
A 4 μm section from each formalin-fixed, paraffinembedded
tumor tissue block containing all morphological
features of the tumor was selected for the study. Colon
carcinoma tissue was added as the positive control, and
benign breast parenchyma was designated as the negative
control. The Ventana Medical System (SN: 714592, Ref:
750-700 Arizona, USA) automated immunohistochemistry
device was used. Immunohistochemical staining was
performed using UltraView Universal DAB Detection Kit
(REF: 760-500, Ventana), and GLUT1 antibody (PA1-
46152, 1/200 diluted, GLUT1 Rabbit Polyclonal Antibody).
The cytoplasmic and membranous staining pattern was
accepted as positive staining for the GLUT-1 antibody.
Specimens were scored according to the intensity of
staining (0- no staining; 1- weak; 2- moderate; 3- strong),
and the extent of tumor cells stained (<10% were scored as 0; 10-25% as 1 point; 26-50% as 2 points; and > 50% as 3
After the evaluation, intensity and extensity scores were
summed up for statistical analysis, and > 2 points were
accepted as positive while ≤ 2 points were considered as
negative GLUT-1 final scores 6 (Figure 1A-D).
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|Figure 1: A) No staining with GLUT-1 antibody (GLUT x400), B) Weak intensity of GLUT-1 immunoreactivity (GLUT x200),
C) Moderate intensity of GLUT-1 immunoreactivity (GLUT x200), D) Strong intensity of GLUT-1 immunoreactivity in tumor (GLUT
Patients with a staining prevalence of more than 1%
for ER and PR were accepted as positive. Patients with
complete membranous staining in more than 10% tumor
cells for HER 2 were accepted as score 3 (positive), weak
to moderate complete membrane staining in more than
10% of tumor cells, or complete membrane staining in less
than 10% of tumor cells were accepted as score 2. More
than 10% incomplete weak membranous staining and no
staining were considered negative. 7,8. Since additional
studies such as SISH and FISH could not be performed at
our center, cases with a HER2 score of 2 were classified
as HER2 status unknown. The Ki-67 proliferation index
was evaluated in the area where the hot spot staining
was observed. A Ki-67 proliferation index ≥14% were
considered as high, and <14% were considered as low Ki-
67 proliferation index 9.
The patients were divided into surrogate subtypes (luminal
A (LA)(ER+, PR+/-, HER2 -, low Ki-67), luminal B (LB)(
ER+, PR+/-, HER2+ or ER+, PR+/-, HER2-, high Ki-67) ,
HER2 (ER-,PR-, HER2+), and triple-negative (TN)( ER-,
PR-, HER2-)) according to the ER, PR, HER2, and Ki-67
immunohistochemical marker staining patterns 10,11. All
patients were divided into histological types according to
the World Health Organization breast cancer classification
11, and graded according to the Nottingham histological
grade scoring system 12.
Statistical analysis was performed using SPSS version
21 software. The compliance of numerical variables to a
normal distribution was evaluated using the Kolmogorov-
Smirnov test and histogram graphics. Continuous variables
not conforming to a normal distribution were compared
between groups using the Mann-Whitney U test. Whether
there was a difference between the groups in terms of
categorical variables was evaluated using the Chi-square
(Pearson Chi-square, Linear-by-linear association) and
Fishers Exact tests. Clinicopathological variables predicting
disease-free survival was investigated by univariate analyzes
using the Log-rank test and Cox regression analysis.
Variables with p<0.2 as determined by univariate analyses
were selected as covariates, and independent risk factors
predicting disease-free survival were analyzed using the backward method Cox regression analysis. Survival rates
were calculated by Kaplan-Meier survival analysis. For
statistical significance, the p value was set as <0.05.
The mean age of the 149 patients was 59.4 (range, 31-
91). The tumor size was 0.5-14 cm, and the mean tumor
diameter was 2.72 cm. 116 of the patients were invasive
ductal carcinomas (IDC), 9 were invasive lobular
carcinomas (ILC), 5 were mixed (ductal and lobular), and
19 were other types (tubular, mucinous, micropapillary,
metaplastic carcinomas) of invasive breast carcinomas.
The clinicopathological features of the patients are shown
in Table I
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|Table I: Association of glucose transporter protein 1 (GLUT-1) expression with clinicopathological parameters in 149 patients who did
not receive neoadjuvant therapy.
GLUT-1 Expression and Clinicopathological Features
GLUT-1 expression was positive in 53% (79/149) of the
patients. According to histological types and molecular
surrogate subtypes, GLUT-1 was expressed at a statistically
higher rate in IDC patients compared to ILC (p <0.001)
(Figure 2A-D). GLUT1 was expressed at a higher rate in
Luminal B, HER 2 and triple negative subtypes, compared
to the Luminal A subtype cases (p <0.001).
GLUT-1 expression was positively correlated with poor
prognostic factors such as ER and PR negativity, high Ki-67
proliferation index, and high histological and nuclear grade
(p <0.001) (Table I).
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|Figure 2: A) Invasive ductal carcinoma, intermediate nuclear grade (HE x200), B) Strong intensity of GLUT-1 immunoreactivity in
invasive ductal carcinoma (GLUT x200), C) Invasive lobular carcinoma (HE x200), D) No staining with GLUT-1 in invasive lobular
carcinoma (GLUT x200).
No statistically significant difference was found between
GLUT-1 expression, and presence of neoadjuvant
chemotherapy (Table II).
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|Table II: Glucose transporter protein 1 (GLUT-1) expression rates by neoadjuvant treatment status.
GLUT-1 Expression and Survival Analysis
The follow-up periods of the patients varied between 8 to
47 months (median 26 months). In the survival analysis,
disease-free survival (DFS) durations were found to be
significantly shorter in patients with GLUT-1 expression
compared to patients without GLUT-1 expression (40,65
months (95% CI: 37.57-43.79) vs. 45.86 months (95% CI
44.26-47.42) (log-rank p: 0.027) (Figure 3). Although
DFS was shorter in patients with GLUT-1 positivity in
univariate analysis; multivariant analysis revealed only size
(>5 cm vs <2 cm) (HR: 31.376; 95% CI: 3.36- 292.968), and
Ki-67 level (HR: 7.61; 95% CI: 1.478- 39.192) to predict low
DFS (Table III, IV).
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|Table III: Univariate analysis results of clinicopathological variables associated with disease-free survival.
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|Table IV: Independent risk factors associated with disease-free survival (Multivariate analysis).
Glucose metabolism is one of the most significant steps in
regulating cellular and systemic homeostasis and tumor
carcinogenesis. Glucose transporter protein families
provide glucose uptake from the systemic circulation into
the cell 5,13,14
. GLUT-1 is the main carrier protein found
in many cells responsible for physiological and pathological
glucose uptake. Their values in these cells change under
physiological and pathological conditions. Especially the
inhibition and activation of RAS, SRC, c-MYC and P53 genes
were associated with GLUT-1 expression levels 15,16
non-neoplastic cells, the p53 gene has been reported to
inhibit GLUT-1 and GLUT-4, and the mutation in the p53 gene has been reported to accelerate glucose transport for
tumor cells by increasing the function of GLUT 17,18
Various studies have shown that the use of GLUT-1
antibodies provides a reduction in tumor size as a result
of apoptosis, and some molecules have an antiproliferative
effect on tumor cells by causing GLUT-1 inhibition 19-21. This situation reveals the close connection between
carcinogenesis and glucose metabolism of tumoral cells
via glucose transporter proteins, and shows that glucose
transporter proteins may be target molecules in cancer
therapy. Targeting this pathway may lead to significant
results in cancer treatment. In addition to these promising
findings of GLUT-1 expression in cancer treatment, it has been also reported that GLUT-1 expression can be
used diagnostically to differentiate benign and malignant
urothelial tumors 22.
The prognostic significance of GLUT-1 expression in
different cancer types such as osteosarcoma, gastric adenocarcinoma,
esophagus adenocarcinoma, pancreatic carcinoma,
lung carcinoma, oral squamous cell carcinoma,
endometrial adenocarcinoma has been reported in numerous
In the meta-analysis of Deng et al. 31, consisting of 1861
breast cancer patients, high GLUT-1 expression levels
correlated with high histological grade, negative ER and
PR, and low survival times. In addition, Krzeslak et al. 32
reported that GLUT-1 expression was observed in 50% of
breast carcinoma patients and that GLUT-1 expression was
detected at a higher rate in poorly differentiated tumors
than well-differentiated tumors. Kang et al. 33 reported
that GLUT-1 expression was associated with negative ER,
PR, and high nuclear grade and poor prognosis in breast
carcinoma patients. Hussein et al. 34 found higher GLUT-
1 expression levels in IDC patients compared to ILC and
mixed ductal and lobular carcinoma patients. In the same
study, GLUT-1 expression was found to be associated with
basal phenotype breast carcinoma with high histological
grade, negative ER and PR, and high p53 expression level.
Similar to the studies reported in the literature, GLUT-
1 expression was higher in Luminal B, HER2 and, triple
negative subtypes compared to Luminal A subtype cases in
our study. Additionally, GLUT-1 expression was found to
be statistically correlated with poor prognostic parameters
such as high histological and nuclear grade, negative ER and
PR expression, and high Ki-67 proliferation index. In the
survival analysis, disease-free survival (DFS) durations were
found to be significantly shorter in patients with GLUT-1
expression. GLUT-1 expression was not associated with
tumor size, axillary lymph node metastasis, angiolymphatic
invasion, perineural invasion, and multicentricity variables.
These findings suggest that the evaluation of GLUT-1
expression in breast cancers may be a promising parameter.
However, studies with larger cohorts and longer follow-up
periods are necessary in order to bring GLUT1 expression
analysis to daily practice.
In our study, GLUT-1 expression was found to be
statistically significantly lower in ILC patients compared to
IDC patients. The reasons for this result might be the energy
metabolism mediated by a different glucose transporter
protein in the development of ILC or low GLUT-1 levels
that cannot be evaluated immunohistochemically in ILC
To our knowledge, there is no study investigating the
relationship between GLUT-1 expression and neoadjuvant
therapy in breast cancer patients. In our study, GLUT-
1 expression was compared in two groups; patients with
or without neoadjuvant therapy. Although GLUT-1
expression was higher in patients receiving neoadjuvant
therapy (71.4% vs. 54%), no significant difference was
observed between these two groups. The reason might be
that current neoadjuvant therapy applications have no
affect over GLUT-1, or the small number of patients with
neoadjuvant therapy in our study.
However, there are limitations in our study in this regard.
In order to determine the relationship between GLUT-
1 expression and neoadjuvant therapy, the comparison
of GLUT-1 expression between the pretreatment core
biopsy and post-treatment surgical materials may be more
decisive. This was not in the design of our study.
In our study, GLUT-1 expression was associated with
pathological poor prognostic factors such as high
histological and nuclear grade, ER and PR negativity, and
low disease-free survival in breast carcinoma patients.
These results suggest that GLUT-1 expression can be
considered as a prognostic marker in breast cancers. It can
be a promising target molecule for personalized treatment
approaches. However, for the GLUT-1 molecule to be used
in daily practice as a prognostic marker, our results should
be supported by studies with longer follow-up periods and
CONFLICT of INTEREST
Authors declare no conflict of interest.
Concept: OO, RB, Design: OO, BŞ, Data collection or
processing: OO, BŞ, ÇÖ, GFG, Analysis or Interpretation:
OO, RB, BŞ, GFG, Literature search: OO, ÇÖ, BŞ, Writing:
OO, ÇÖ, Approval: OO, RB, ÇÖ, GFG, BŞ.
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