COMPARISON BETWEEN CELLS AND CANCER STEM-LIKE CELLS
ISOLATED FROM GLIOBLASTOMA AND ASTROCYTOMA ON
EXPRESSION OF ANTI-APOPTOTIC AND MULTIDRUG
RESISTANCE–ASSOCIATED PROTEIN GENES
F. JIN,a
L. ZHAO,b
* H.-Y. ZHAO,a
S.-G. GUO,c
J. FENG,a
X.-B. JIANG,a
S.-L. ZHANG,b
Y.-J. WEI,a
R. FUa
AND
J.-S. ZHAOa
a
Department of Neurosurgery, Union Hospital, Tongji Medical College,
Huazhong University of Science and Technology, Wuhan, 430022, PR
China
b
Department of Hepatology and Infectious Disease, Union Hospital,
Tongji Medical College, Huazhong University of Science and Technology,
Wuhan, 430022, PR China
c
Department of Neurology, Shandong Provincial Hospital, Jinan,
250021, PR China
Abstract—This study is to explore and compare the features
of the cells and cancer stem-like cells (CSCs) isolated from
both glioblastoma and astrocytoma on expression of anti-apoptotic
and multidrug resistance–associated protein (MRP)
genes. As a result, the mRNA expression of livin, livin␣ and
MRP1 was up-regulated in human CSCs from 2 times to 85
times, but the gene expression of MRP3 was down-regulated
from 0.09 times to 0.5 times. After just differentiation the
mRNA expression of livin, livin␣ and MRP3 was up-regulated
from9 times to 64 times, but the mRNA expression of MRP1
was down-regulated from 0.01 times to 0.03 times. It is a rare
report that glioma stem-like cells can be induced successfully
from a grade 2–3 astrocytoma tissue. The properties of
glioblastoma and astrocytoma stem-like cells on anti-apoptotic
and MRP genes are: anti-apoptotic gene livin and survivin
are elevated in CSCs but are the most increased in just
differentiated CSCs; MRP1 gene is significantly increased
and MRP3 is decreased in CSCs, but when differentiating the
MRP3 gene starts a remarkable increase in CSCs; the expression
of anti-apoptotic and MRP genes shows no differences
between the CSCs isolated from glioblastoma and astrocytoma
tissues. © 2008 IBRO. Published by Elsevier Ltd. All
rights reserved.
Key words: glioma, cancer stem-like cell, glioblastoma, astrocytoma,
livin, multidrug resistance–associated protein.
Gliomas are the most common type of primary brain tumor.
Nearly two-thirds of gliomas are highly malignant lesions
that account for a disproportionate share of brain tumor–
related morbidity and mortality (Sathornsumetee et al.,
2007). Despite recent advances, 2-year survival for glioblastoma
with optimal therapy is less than 30%. While
surgery, radiation therapy and chemotherapy have roles to
play in the treatment of patients with gliomas, these therapies
are self-limited because of the intrinsic resistance of
glioma cells to therapy, and the diffusely infiltrating nature
of the lesions (Nakada et al., 2007). Even among patients
with low-grade gliomas that confer a relatively good prognosis,
treatment is almost never curative (Norden and
Wen, 2006). Though the last decade produced a number
of important advances, some of which have translated
directly into survival benefits, the prognosis for many patients
with gliomas is poor.
It is now known that malignant gliomas arise from a
number of well-characterized genetic alterations and activations
of oncogenes and inactivation of tumor suppressor
genes. Those genetic alterations disrupt critical cell cycle,
growth factor activation, apoptotic, cell motility, and invasion
pathways that lead to phenotypic changes and neoplastic
transformation (Bansal et al., 2006). Recently, the
concept of cancer stem cells was focused on increasingly
(Schulenburg et al., 2006). The findings of brain cancer
stem cells were made by applying the principles for cell
culture and analysis of normal neural stem cells (NSCs) to
brain cancer cell populations and by identification of cell
surface markers that allow for isolation of distinct cancer
cell populations that can then be studied in vitro and
in vivo. A population of brain cancer cells can be enriched
for brain cancer stem cells by cell sorting of dissociated
suspensions of cancer cells for the NSC marker CD133.
These CD133 positive cells, which also expressed the
NSC marker nestin, but not differentiated neural lineage
markers, represent a minority fraction of the entire brain
cancer cell population, and exclusively generate clonal
cancer spheres in suspension culture and exhibit increased
self-renewal capacity (Singh et al., 2004a). Moreover,
progressive explorations have discovered CD133
positive cancer stem cells have a capacity for unlimited
self-renewal, as well as the ability to initiate and drive
tumor progression in an animal model (Singh et al.,
2004b). The cell-membrane protein CD133 has been identified
as a marker of a subset of NSCs in the adult CNS as
well as of glioma stem or stem-like cells (Bao et al., 2006;
Singh et al., 2003, 2004b).
In gliomas, WHO (World Health Organization) system
assigns a grade from 1 to 4, with one being the least
*Corresponding author. Tel: ϩ86-27-62717387; fax: ϩ86-27-84848153.
E-mail address: chinesemd@hotmail.com (L. Zhao).
Abbreviations: ACC, autologous cancer cell; bFGF, basic fibroblast
growth factor; CSC, cancer stem-like cell; Ct, cycle threshold; DMEM/
F12, Dulbecco’s modified Eagle’s medium/nutrient mixture F-12
Ham’s; EGF, epidermal growth factor; FBS, fetal bovine serum; GFAP,
glial fibrillary acidic protein; IAP, inhibitor of apoptosis protein; LIF,
leukemia inhibitory factor; MRP, multidrug resistance–associated protein;
NSC, neural stem cell; PBS, phosphate-buffered saline; WHO,
World Health Organization.
Neuroscience 154 (2008) 541–550
0306-4522/08$32.00ϩ0.00 © 2008 IBRO. Published by Elsevier Ltd. All rights reserved.
doi:10.1016/j.neuroscience.2008.03.054
541
aggressive and four being the most aggressive. Glioblastoma,
also called grade 4 astrocytoma, glioblastoma multiforme,
is a fast-growing type of CNS tumor that forms
from glial (supportive) tissue of the brain and spinal cord
and has cells that look very different from normal cells.
Astrocytoma is a tumor that begins in the brain or spinal
cord in small, star-shaped cells called astrocytes and includes
WHO grades 1–3. As in the past all glioma stemlike
cells were isolated from glioblastoma, astrocytoma
stem cells have not been known so far, and the properties
of stem-like cells isolated from glioblastoma and astrocytoma
on expression of anti-apoptotic and multidrug resistance–associated
protein (MRP) genes have not been
compared before.
Thereby, we cultured and disassociated cancer stemlike
cells (CSCs) from the cell lines and tumor mass of
inpatients suffering from both glioblastoma and astrocytoma,
and explored the anti-apoptotic and drug resistant
gene expression in order to find novel properties of those
CSCs.
EXPERIMENTAL PROCEDURES
Chemicals and reagents
Dulbecco’s modified Eagle’s medium/nutrient mixture F-12 Ham’s
(DMEM/F12) with high glucose medium was purchased from HyClone
(Logan, UT, USA). Fetal bovine serum (FBS), trypsin, B-27
(1ϫ) serum-free supplements were from Gibco (Grand Island, NY,
USA). Epidermal growth factor (EGF), basic fibroblast growth
factor (bFGF), leukemia inhibitory factor (LIF) was obtained from
Peprotech (Rocky Hill, NJ, USA). Rabbit anti-human nestin, rabbit
anti-human glial fibrillary acidic protein (GFAP) and mouse antihuman
␤-tubulin antibody were from Santa Cruz Biotechnology
(Santa Cruz, CA, USA). Goat anti-mouse IgG-FITC antibody and
goat anti-rabbit IgG-FITC antibody were from Sigma (St. Louis,
MO, USA). CD133 cell isolation kit (MACS method) was purchased
from Miltenyi Biotec GmbH (Bergisch Gladbach, Germany).
Tumor specimens and primary cell culture
Glioma specimens were collected from 17 inpatients in China
Wuhan Union Hospital and their pathological diagnoses were
brain glioma. In those patients 10 subjects were of glioblastoma
and the others suffered from astrocytoma. The exsected tissues
were washed twice with D-Hanks’ solution in aseptic condition.
After clearing out of visible blood vessel and necrotic tissue, the
glioma tissues were sheared into paste by eye scissors. Then
following digestion with 0.25% trypsin for 20 min and blown and
stirred by pipette, cell suspension was made prior to terminating
digestion by 10% FBS. The suspension was filtered through a
200-mesh sieve and centrifuged at 1000 r.p.m. After disposing of
supernatant, the primary glioma cells were washed again with
serum-free medium. Then having been centrifuged, the cells were
collected and inoculated into a serum-free medium (NSC medium)
which contained DMEM/F12 with high glucose medium, 20 ng/mL
EGF, 20 ng/mL bFGF, 10 ng/mL LIF and b27 (1ϫ). Last, the cells
were placed in incubator on conditions of 37 °C, 5% CO2 and
saturated humidity. Every 3–4 days the medium was renewed.
Then the induced glioma stem-like cells were cultured in conditions
of DMEM/F12 with high glucose medium with 10% FBS for
inducing differentiation. The use of human tissue was authorized
by the Ethics Committee of Tongji Medical College, Huazhong
University of Science and Technology.
Glioma cell line culture
Glioblastoma U251 cell line was provided by the China Center for
Typical Culture Collection (CCTCC) (Wuhan, China). Astrocytoma
GL15 cell line was kindly provided by Institute of Neuroscience,
Tongji Medical College, Huazhong University of Science and
Technology. The two cell lines were cultured in the same conditions
as the primary cell culture.
Isolation of CD133 positive glioma stem-like cells
After the neurospheres grew a large amount, the spheres were
collected and the CD133 positive cells were separated by
magnetic cell sorting technique (MACS). The sorting process
was conducted according to the instruction of the CD133 cell
isolation kit.
Immunofluorescence staining on glioma tumor
stem cells
The well-grown cell spheres were selected for growing on the
slides which were coated by polylysine. After drying at 37 °C, the
slides were washed by phosphate-buffered saline (PBS) three
times in order to clear up medium. At room temperature, the cells
were fixed by paraform for 30 min, and then were washed by PBS
again three times. After blocked by 5% goat serum at 37 °C for 30
min, rabbit anti-human nestin (1:200) (1st antibody) was added
and the cells were placed in a wet box for one night. The day
following PBS washing, goat anti-rabbit IgG-FITC antibody (2nd
antibody) was added for incubation for 30 min at 37 °C. Meanwhile
a negative control in which PBS was used instead of the 1st
antibody was performed. The slides were observed with an OlymA
B
Fig. 1. Glioma tissues with HE staining (20ϫ10). (A) Glioblastoma tissue (No.912110); (B) astrocytoma (WHO 2–3 grade) tissue (No. 916718).
F. Jin et al. / Neuroscience 154 (2008) 541–550542
pus BX51 fluorescence microscope. The procedure of immunofluorescent
assay on GFAP and ␤-tubulin on differentiated glioma
stem cells followed the course of nestin except for respective
related antibodies.
Real-time quantitative RT-PCR
The samples were collected and each 50–100 mg tissue samples
or 106
cell samples were collected and added 1 mL TRIzol (Jin et
al., 2008). The total RNA from glioma cells and glioma stem cells
was prepared by adding TRIzol Reagent (Gibco BRL) according to
manufacturer’s protocol. The RNA solution was stored at Ϫ80 °C
until used. All reactions were performed in duplicate with a negative
control (no template) and the mean value of the threshold
cycle (the start of exponential amplification) of each sample was
normalized with the threshold cycle of glyceraldehyde-3-phosphate
dehydrogenase (GAPD), obtaining the ⌬ cycle threshold
(Ct) value. Quantitative PCR was performed in ABI-7700 Sequence
Detector (Applied Biosystems, Foster City, CA, USA). The
reverse transcription was performed with M-MLV reverse transcriptase.
The reverse transcriptional reaction system included:
5.5 ␮L H2O, 1.0 ␮L Oligo(dT18) (50 ␮g/mL), total RNA 6.0 ␮L,
70 °C 5 min to ice for unfolding the secondary structure of mRNA;
0.5 ␮L RNasin (40 U/␮L), 4.0 ␮L 5ϫ buffer, 2.0 ␮L dNTP (10 mM),
1.0 ␮L RTase (200 U/␮L), 42 °C 60 min to 95 °C 5 min to 4 °C.
A B
Fig. 2. Normal glioma cells (10ϫ10). (A) Normally cultured GL15 cells. (B) Normally cultured U251 cells.
BA
DC
Fig. 3. Glioma cells cultured from tissues and cell lines (20ϫ10). (A) Primary cells derived from glioblastoma tissue (No. 912110) at the 5th culturing
day in NSC medium. (B) Primary cells derived from astrocytoma tissue (No. 916718) at the 5th culturing day in NSC medium. (C) GL15 cells at the
3rd culturing day in NSC medium. (D) U251 cells at the 3rd culturing day in NSC medium.
F. Jin et al. / Neuroscience 154 (2008) 541–550 543
Real time PCR reaction was performed with SYBR GreenIfluorochrome.
The standard curve was obtained and Ct value was
calculated. Each 50 ␮L PCR system contained 1/50 of the original
cDNA, 7 ␮L (25 mM) MgCl2, 0.8 ␮L (20 pmol/␮L) of each primer,
1 ␮L (10 mM) dNTP, 1 ␮L SYBR GreenI, 0.5 ␮L (5 U/␮L) TaqDNA
polymerase (Promega, Madison, WI, USA) and 5 ␮L 10ϫ buffer.
Fifty cycles of amplification were performed: after 94 °C 3 min,
reaction cycle with 94 °C, 30 s, to 57 °C, 30 s, then to 72 °C, 30 s
was carried out. The fluorescence signal was detected at the end
of each cycle. Melting curve analysis was used to confirm the
specificity of the products. The 2Ϫ⌬⌬CT
method was performed to
analyze the results (Livak and Schmittgen, 2001). The primer was
as below:
Homo-livin
Forward: 5=-ACAGAGGAGGAAGAGGAGGAGG-3=
Reverse: 5=-GCAGTCAGCGGCCAGTCATAG-3=
Homo-livin␣
Forward: 5=-CTGTCAGTTCCTGCTCCGGTC-3=
Reverse: 5=-GGGCTCAAGAACCCACCAC-3=
Homo-survivin
Forward: 5=-ACTGCCCCACTGAGAACGAGC-3=
Reverse: 5=-AAGGAAAGCGCAACCGGACGAAT-3=
Homo-MRP1
Forward: 5=-CACCACTGGAGCATTGACTACC-3=
Reverse: 5=-GTAATTACAGCAAGCCTGGAACC-3=
Homo-MRP3
Forward: 5=-CCTGTATGTGGGTCAAAGTGCG-3=
Reverse: 5=-CCCAGCCTCAGGGAAGTGTTG-3=
Homo-␤-actin
Forward: 5=-CTTAGTTGCGTTACACCCTTTCTTG-3=
Reverse: 5=-CTGCTGTCACCTTCACCGTTCC-3=
Statistical analysis
Each test was perform and then repeated two times. The data
were normalized as ratio of CSC/ACC (autologous cancer cells).
The data were presented as meanϮS.D. Comparisons of the data
were performed with Student t-test. Statistical significance was
considered significant when PϽ0.05. The statistical process was
performed with SPSS 12.0 software.
RESULTS
Induction of glioma stem-like cells
We found that the primary cancer cells from two tissues,
U251 and GL15 cell line (Figs. 1, 2 and 3) could become
floating neurospheres by NSC-medium cultivation. When
cultured in NSC medium at the 7th–10th culturing day, the
floating neurospheres emerged from primary glioma cells,
while at the 5th–7th culturing day the GL15 cells produced
neurospheres and at the 15th–20th culturing day the U251
cell generated neurospheres (Fig. 4). By CD133 isolation,
glioma stem-like cells were induced successfully from two
glioma specimens from one glioblastoma (No. 912110)
and one grade 2–3 astrocytoma subject (No. 916718), and
from U251 and GL15 cell lines (Fig. 5). The CSCs which
were cultured in NSC medium grew in suspension and
presented the features of stem cells: sphere-like shape,
self-renewal and ability to differentiate. Nestin immunoflu-
BA
DC
Fig. 4. Neurospheres emerged from primary cells and cell lines (20ϫ10). (A) Neurospheres emerged from primary glioblastoma cells (No. 912110)
at the 7th culturing day in NSC medium. (B) Neurospheres emerged from astrocytoma cells (No. 916718) at the 7th culturing day in NSC medium.
(C) Neurospheres emerged from GL15 cells at the 5th culturing day in NSC medium. (D) Neurospheres emerged from U251 cells at the 15th culturing
day in NSC medium.
F. Jin et al. / Neuroscience 154 (2008) 541–550544
orescence staining of the stem-like cells presented positive
but the glioma cells did not show this feature (Fig. 6).
Differentiation of glioma stem-like cells
The induced glioma stem-like cells started to differentiate
after culture conditions of DMEM/F12 medium with 10%
FBS. At the 4th hour after culture, the stem-like spheres
derived from glioma tissues adhered to the wall and dendrite-
or axon-like pseudopodia emerged at the surface of
spheres. At the 3rd–5th day, thick dendrite-like pseudopodia
grew from all the spheres. As a contrast, the stem-like
cells cultured by NSC medium did not show the similar
changes. The differentiated cells presented positive ␤-tubulin
and GFAP stain but the glioma stem-like spheres did
not show this feature (Fig. 7).
Comparison of anti-apoptotic and MRP gene
expression between glioma CSC and ACC
As shown in Table 1, the mRNA expression of livin, livin␣
and MRP-1 was up-regulated in CSCs in both glioma
primary cells and cell lines from 2 times to 62 times in CSC
derived from cell line and 2 times to 85 times CSC from
primary tissues, but the gene expression of MRP-3 was
down-regulated from 0.09 times to 0.5 times. The trends of
livin␤ were also coincident with livin␣ according to the
changes of livin and livin␣. The increasing extent from
GL15 cell line was significantly more than that from U251
cell line (PϽ0.01) but the difference did not exist between
the CSC from two tissues.
Comparison of anti-apoptotic and MRP gene
expression between CSC before and after
differentiation
As shown in Table 2, the mRNA expression of livin, livin␣
and MRP-3 was up-regulated after differentiation in CSC
deriving from both glioma specimens from9 times to 64
times. The trends of livin␤ were also coincident with livin␣
according to the changes of livin and livin␣. However, the
mRNA expression of MRP-1 was down-regulated from
0.01 times to 0.03 times.
DISCUSSION
Stem cells are defined by their ability to self-renew, proliferate,
and generate progeny that differentiate into the multiple
cell types that make up the tissue from which they are
derived. The hypothesis that certain cancers may be the
result of unregulated stem cells is founded on the suggested
similarities between cancer stem cells and somatic
stem cells (Ghods et al., 2007). Recently, it has been
confirmed by identification of brain cancer stem cells by
CD133 (Bao et al., 2006; Singh et al., 2003, 2004b). Identification
of brain cancer stem cells provides a powerful tool
for the investigation of the tumorigenic process in the CNS,
A B
DC
Fig. 5. Stem-like cell sphere derived from primary cells and cell lines (20ϫ10). (A) Stem-like cell sphere derived from glioblastoma tissue (No.
912110). (B) Stem-like cell sphere derived from astrocytoma tissue (No. 916718). (C) Stem-like cell sphere derived from GL15 cell line. (D) Stem-like
cell sphere derived from U251 cell line.
F. Jin et al. / Neuroscience 154 (2008) 541–550 545
BA
DC
FE
HG
Fig. 6. Nestin immunofluorescence staining (green fluorescence was positive) on glioma stem-like cell spheres and glioma cells (40ϫ10). (A) On
spheres derived from glioblastoma tissue (No. 912110). (B) On cells from glioblastoma tissue (No. 912110). (C) On spheres derived from astrocytoma
tissue (No. 916718). (D) On cells from astrocytoma tissue (No. 916718). (E) On spheres derived from GL15 cells. (F) On GL15 cells. (G) On spheres
derived from U251 cells. (H) On U251 cells.
F. Jin et al. / Neuroscience 154 (2008) 541–550546
and will be crucial in developing therapies that use brain
cancer stem cells as a target (Singh et al., 2004a).
In our research, we successfully separated CD133
positive cells from glioblastoma, astrocytoma tissues and
U251, GL15 cell line, and found the separated cells presented
properties of cancer stem cells: sphere-like form,
self-renewal, ability to differentiate. Especially, we induced
primary glioma stem-like cells from two samples of glioma
subjects. One was diagnosed as WHO grade 2–3 astrocytoma.
So far almost all glioma stem-like cells have been
cultured from glioblastoma tissue. It is a rare report that
glioma stem-like cells can be induced from astrocytoma.
The finding suggests a mildly malignant tumor still has
potential abilities to develop into highly malignant cancer
and a clear eradication for cancer tissue is necessary in
clinic.
As discovered now, cancer stem cells are a very small
group of cells in the tumor bulk. Thereby inducing cancer
stem cells from cancer tissue is not easy work and a successful
induction is limited by operational technology, such as
the successful rate of primary cell culture, cell survival condition
and so on. Our induction rate is similar to the literature
(Liu et al., 2006). More effective methods will be
developed in the future.
We further checked the other properties of glioma
stem-like cells on our separated cells. Nestin was selected
A
B C
ED
Fig. 7. GFAP and ␤-tubulin immunofluorescence staining (green fluorescence was positive) on differentiated and undifferentiated glioma stem-like
cells (20ϫ10). (A) Differentiated glioma stem-like cell. (B) GFAP immunofluorescence staining on differentiated glioma stem-like cell. (C) GFAP
immunofluorescence staining on undifferentiated glioma stem-like cell. (D) ␤-Tubulin immunofluorescence staining on differentiated glioma stem-like
cell. (E) ␤-Tubulin immunofluorescence staining on undifferentiated glioma stem-like cell.
F. Jin et al. / Neuroscience 154 (2008) 541–550 547
to examine the feature of our separated glioma stem-like
cells. Nestin is a marker of progenitor cells or precursor
cells and now is recognized as a protein marker of NSCs
(Hoffman, 2007; Hwang et al., 2007). Many researches
chose nestin as a marker to check the properties of brain
CSCs. Recent findings also showed nestin has an upregulated
expression in glioma stem cells. In our research,
the separated cells were nestin positive, which could support
that our induced CD133 positive cells were CSCs. We
further cultured the tumor stem cells by NSC medium and
found this method could maintain growth of the CSCs.
After being induced to differentiation by culture with
DMEM/F12 medium, the CSCs from both cancer tissue
and glioma cell lines presented GFAP and ␤-tubulin positive.
As GFAP is the astrocyte lineage marker and ␤-tubulin
is considered as the neuronal lineage marker (Ghods et
al., 2007), it could be implied that our induced CD133
positive cells had the potential to differentiate into astrocytes
and neurons, which shows the cells possess the
property to differentiate into different ACCs.
The inhibitor of apoptosis protein (IAP) family encodes
a group of baculovirus IAP repeat domain (BIR) –containing
proteins that suppress apoptosis (Huang et al., 2006).
Survivin is an important member of IAP. This protein is
highly expressed in most cancers and associated with
chemotherapy resistance, increased tumor recurrence,
and shorter patient survival, but rarely is expressed in
terminally differentiated adult tissues (Fukuda and Pelus,
2006). Current documents show that biological functions of
survivin include inhibition of apoptosis, promotion of mitosis,
angiogenesis, which play a causative role in cancer
formation and/or progression (Duffy et al., 2007). In our
research, it was observed that gene expression of the
member of IAP was up-regulated in CSCs, which implies
the glioma stem-like cells are a main factor to resist cancer
apoptosis and maintain cancer growth and angiogenesis.
Furthermore, it was also investigated that survivin continued
rising in differentiated glioma stem-like cells. It has
been reported that survivin expresses more highly in glioma
CSCs (Ghods et al., 2007). Inferred by our finding, the
anti-apoptotic gene is the most highly expressed in just
differentiated glioma CSCs, which presents a more detailed
profile of survivin expression in glioma stem-like
cells.
Livin is also a member of the IAP family of caspase
inhibitors that selectively binds the endogenous IAP antagonist
(second mitochondria-derived activator of caspases)
SMAC and caspase-3, caspase-7, and caspase-9, which
encode negative regulatory proteins that prevent cell apoptosis
(Chang and Schimmer, 2007). Livin is selectively
expressed in the most common human neoplasms and
appears to be involved in tumor cell resistance to chemotherapeutic
agents (Liu et al., 2007; Kempkensteffen et al.,
2007). In our research, it was observed that gene expression
of livin and livin␣ was up-regulated in CSCs. As livin
contains two isoforms: livin␣ and livin␤, it could be deduced
that livin␤ had a similar elevating expression to
livin␣ in the CSCs and differentiated CSCs. Like survivin
the rising expression of livin in glioma stem-like cells also
shows its causative role for anti-apoptosis and anti-chemotherapy
by inhibiting the function of SMAC and caspase
molecules. Furthermore, the fact the highest expression of
livin in differentiated CSCs also demonstrates the just
differentiating or having differentiated glioma stem-like
cells are the most tolerant stage to promote growth of
cancer cells and to resistant apoptosis and chemotherapeutic
drugs.
The findings of survivin and livin expression in CSC
and just differentiated CSC suggest that the group of CSC
may be the highest malignant cell population in cancer
bulk. This can be interpreted this way: a relapsing cancer
is more malignant after treatments because the relapsing
cancer tissue may be developed from uneliminated cancer
cells, cancer stem cells.
MRP is a 180- to 195-kDa membrane protein associated
with resistance of human tumor cells to cytotoxic
drugs (Zaman et al., 1994). Numerous members of the
Table 1. Anti-apoptotic and MRP gene expression on glioma CSC compared to that on ACC
Gene name Glioblastoma No. 912110 Astrocytoma No. 916718 GL15 U251
ACC CSC ACC CSC ACC CSC ACC CSC
Livin 1 52.543Ϯ4.281 1 57.084Ϯ5.362 1 6.695Ϯ0.437* 1 3.912Ϯ0.231
Livin␣ 1 11.574Ϯ0.852 1 34.279Ϯ2.935 1 62.336Ϯ5.017* 1 8.699Ϯ0.779
Survivin 1 2.457Ϯ0.205 1 1.943Ϯ0.138 1 4.867Ϯ0.403* 1 2.972Ϯ0.275
MRP-1 1 64.287Ϯ7.803 1 85.736Ϯ8.754 1 54.042Ϯ4.772* 1 2.015Ϯ0.183
MRP-3 1 0.094Ϯ0.004 1 0.275Ϯ0.017 1 0.533Ϯ0.038 1 0.453Ϯ0.047
The value of ACC was normalized as 1 and the value of CSC was expressed as relative value.
* PϽ0.01 compared to the value of CSC in U251 group.
Table 2. Anti-apoptotic and MRP gene expression on CSC compared
to that on differentiated stem-like cells (DSC)
Gene name Glioblastoma No.
912110
Astrocytoma No.
916718
CSC DSC CSC DSC
Livin 1 24.783Ϯ2.038 1 17.695Ϯ1.894
Livin␣ 1 57.784Ϯ5.832 1 82.196Ϯ7.539
Survivin 1 12.853Ϯ1.439 1 9.361Ϯ1.474
MRP-1 1 0.037Ϯ0.002 1 0.014Ϯ0.003
MRP-3 1 64.739Ϯ5.961 1 52.673Ϯ6.197
The value of CSC was standardized as 1 and the value of DSC was
expressed as relative value.
F. Jin et al. / Neuroscience 154 (2008) 541–550548
multidrug resistance associated protein family serve as
export pumps that prevent the accumulation of anionic
conjugates and glutathione disulfide (GSSG) in the cytoplasm,
and play, therefore, an essential role in detoxification
and defense against oxidative stress (Homolya et al.,
2003). The 190 kDa multidrug resistance protein MRP1 is
involved in the multidrug resistance phenotype of human
gliomas (Benyahia et al., 2004). In gliomas, mainly MRP1
has been studied thus far and was found to be localized to
the tumor vasculature and partially also to the tumor cells
(Mohri et al., 2000; Aronica et al., 2003; Andersson et al.,
2004; Benyahia et al., 2004). In glioma cell lines, MRP1 is
shown to confer resistance to various anticancer drugs
(Benyahia et al., 2004; Bronger et al., 2005). Apart from
MRP1, some research showed gene MRP3 is hyperexpressed
in astrocytomas for the primary resistance to chemotherapy
(Calatozzolo et al., 2005) and MRP3 can modulate
drug sensitivity to certain anticancer agents in human
gliomas (Haga et al., 2001). We detected MRP1 and
MRP3 gene expression in both glioma stem-like cells and
autologous cancer cells and found MRP1 was the most
highly expressed in glioma stem-like cells and MRP3 was
much less expressed in CSCs, which was different from
the past reports (Salmaggi et al., 2006). That is to say,
MRP1 plays a more significant role as multidrug resistance
transporter than MRP3 in glioma stem-like cells. However,
after differentiation, the expression of MRP3 notably rose,
which showed when just differentiating or having differentiated,
the cells perform resisting chemotherapeutics via
MRP3 function. As the MRP family has been considered
as a target for reducing chemotherapeutic drug resistance,
the variation of MRPs in CSCs may be important in the
future therapeutic strategies.
GL15 cell line is derived from glioblastoma (Bocchini et
al., 1991), while the U251 cell line is cultured from astrocytoma
(Akhyani et al., 2006). We compared the gene
expression between those two cell lines on livin, survivin
and MRP1 and found more up-regulations of those genes
existed in CSCs derived from the GL15 cell line, which is
coincident with malignant degree of glioblastoma. However,
the same trends did not occur in glioma stem-like
cells derived from tissues, which showed a more complicated
influence in human body and the malignant difference
between glioblastoma and astrocytoma is not due to
the tested anti-apoptotic and MRP genes.
Cancer is among the leading causes of morbidity and
mortality in the world (Jin et al., 2008). Despite recent
advances, most therapeutic approaches fail to eradicate
the entire neoplastic clone. The remaining cells often develop
metastasis and/or recurrences and therefore may
represent attractive targets of therapy. In this research, we
successfully induced and cultured CSCs from both glioma
tissues and cell lines. Especially, we induced tumor stem
cells from astrocytoma tissue. Moreover, we found the
properties of human brain glioma stem-like cells: antiapoptotic
gene is elevated in glioma stem-like cells but is
the most increased in just differentiated glioma stem-like
cells; MRP1 gene is significantly increased but MRP3 is
decreased in glioma stem-like cells, and when differentiating
the MRP3 gene starts a remarkable increase in glioma
stem-like cells; but the difference of malignant grade between
glioblastoma and astrocytoma is not due to the
tested anti-apoptotic and MRP genes.
Acknowledgments—This study is sponsored by the China Shandong
Provincial Development Program of Medical Science and
Technology (No. 2007HZ019) and Jining City Development Program
of Science and Technology (No. 2006-11-33).
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(Accepted 15 March 2008)
(Available online 1 April 2008)
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