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Acta Biochim Biophys Sin, 2017, 1–10
doi: 10.1093/abbs/gmx099
Original Article
Original Article
Immature colon carcinoma transcript-1
promotes proliferation of gastric cancer cells
Zishu Wang†,*, Gongsheng Jin†, Qiong Wu*, Rui Wang, and Yumei Li
Department of Medical Oncology, The First Affiliated Hospital of Bengbu Medical College, Bengbu, Anhui 233004,
China
†
These authors contributed equally to this work.
*Correspondence address. Tel/Fax: +86-552-3074480; E-mail: zishuwang@163.com (Z.W.)/qiongwu68@aliyun.com (Q.W.)
Received 22 February 2017; Editorial Decision 22 June 2017
Abstract
Gastric cancer is the fourth most common malignant tumor and has been considered as one of
the leading causes of cancer-related death worldwide. The identification of the molecular mechanism during gastric cancer progression is urgently needed, which will help to develop more
effective treatment strategies. As a component of the human mitoribosome, immature colon carcinoma transcript-1 (ICT1) might be involved in tumor formation and progression. However, its
biological function and the corresponding mechanism in gastric cancer have been poorly characterized. To study the mechanism of ICT1 in gastric cancer, we first investigated the mRNA
levels of ICT1 in human normal and gastric cancer tissues using datasets from the publicly available Oncomine database. The results showed that ICT1 is overexpressed in gastric cancer tissues. Then in order to study the role of ICT1 in gastric cancer, two shRNAs were used to silence
ICT1 in MGC80-3 and AGS cells. Functional analysis showed ICT1 knockdown significantly inhibited the proliferation of gastric cancer cells and induced apoptosis. Further, mechanistic study
demonstrated that ICT1 silencing induced cell-cycle arrest at G2/M phase via the suppression of
cyclin A2 and cyclin B1. In addition, ICT1 silencing also increased cleaved caspase-3 and activated PARP in gastric cancer cells. These findings suggest that ICT1 may play a crucial role in
promoting gastric cancer proliferation in vitro.
Key words: Gastric cancer, ICT1, shRNA, cell proliferation, apoptosis
Introduction
Gastric cancer, as the fourth most common malignant tumor, has
been considered as one of the leading causes of cancer-related
death worldwide [1,2]. Despite the advancement of surgical techniques and instruments, it is still difficult to completely cure gastric
cancer patients at middle-late stage [3]. Statistical analysis indicates
that ~40%–60% gastric cancer patients will often have postoperative recurrence after undergoing gastric cancer radical operation [4]. Recently, investigators have demonstrated that gastric
carcinogenesis is closely associated with various genetic alterations,
including oncogenes and tumor suppressor genes. Therefore, the
identification of the molecular mechanism underlying gastric
cancer progression might provide more effective treatment strategies for this malignancy.
Immature colon carcinoma transcript-1 (ICT1), as a component
of the human mitoribosome, was initially identified between undifferentiated and differentiated human colon carcinoma cell lines HT29D4 and Caco-2 [5,6]. It is also an essential peptidyl-tRNA hydrolase
component of the large subunit of the ribosome, indicating a strong
association of ICT1 with protein synthesis. As a novel protein, ICT1
has been shown to pull down many mitochondrial ribosomal proteins using immunoprecipitation analysis [7,8]. Human mitochondria are essential for cell metabolism as ubiquitous organelles.
Mitochondrial dysfunction by genetic alterations results in cell
© The Author 2017. Published by Oxford University Press on behalf of the Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese
Academy of Sciences. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com
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proliferation inhibition and apoptosis [9]. As an essential mitochondrial protein, depletion of ICT1 causes a reduction of mitochondrial
protein synthesis, leading to a loss of cell viability [10]. In agreement
with these facts, previous studies have recognized that ICT1 is implicated in promoting cell proliferation by affecting cell-cycle progression
and apoptosis. ICT1 promotes colorectal cancer growth via the intracellular AMPK, SAPK/JNK, and PARP signaling pathways, and high
ICT1 means more invasive tumors and worse prognosis [11].
Knockdown of ICT1 in glioblastoma multiforme was found to inhibit
cell proliferation by arresting cell-cycle at G2/M phase [12]. In prostate
cancer cells, ICT1 leads to cell-cycle arrest and induces apoptosis
through mediating Bcl-2 family protein [13]. These findings together
implicate that ICT1 might be involved in tumor genesis, formation and
The role of ICT1 in gastric cancer cells
progression. Although the status of ICT1 has been well described in
several types of cancer, its role in gastric cancer still remains unclear.
In the present study, we aimed to investigate the biological
functions of ICT1 in gastric cancer progression. The mRNA levels
of ICT1 were first investigated in human normal and gastric cancer tissues using the datasets from Oncomine database. Then
lentivirus-mediated RNA interference was used to down-regulate
ICT1 expression to carry out loss-of-function assays. It was shown
that knockdown of ICT1 could suppress the proliferation of gastric cancer cells via inducing cell-cycle arrest, promoting apoptosis, and affecting the expression of related proteins. These
findings will provide a novel insight into the development of
experimental therapies for gastric cancer.
Figure 1. Fold change in ICT1 expression between three types of adencarcinoma vs. gastric mucosa and gastric tissue using the Oncomine database
Comparison was divided into six studies according to the source of specimen and P -values were indicated.
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The role of ICT1 in gastric cancer cells
Materials and Methods
Analysis of oncomine data
In order to determine the expression of ICT1 in human, we performed data mining using Oncomine database (www.oncomine.org).
The gene expression of ICT1 was compared between cancer tissues
with normal gastric tissues according to the standard procedures as
previously described [14].
Cell lines and cell culture
The human gastric cancer MGC80-3, AGS and the human embryonic
kidney 293 T (HEK293T) cell lines were obtained from the Cell Bank
of Chinese Academy of Science (Shanghai, China). MGC80-3 and
AGS cells were cultured at 37°C in RPMI 1640 medium (GIBCOBRL, Grand Island, USA) supplemented with 10% fetal bovine serum
(FBS; Biowest, Nuaillé, France). HEK293T cells were cultured in
Dulbecco’s modified Eagle’s medium (DMEM; GIBCO-BRL)
containing 10% FBS. All cell lines were maintained in a fully humidified atmosphere of 95% O2 and 5% CO2.
Construction of lentiviral vectors
According to the ICT1 sequence downloaded from NCBI
(NM_001545), two shRNA sequences (Genewiz, New York, USA) (S1:
5′-GCAGAATGTGAACAAAGTGAACTCGAGTTCACTTTGTTCAC
ATTCTGCTTTTTT-3′ and S2: 5′-GCTGTTAATGCTTGTCTATAAC
TCGAGTTATAGACAAGCATTAACAGCTTTTTT-3′) targeting ICT1
and a control shRNA sequence (5′-TTCTCCGAACGTGTCACGTCTC
GAGACGTGACACGTTCGGAGAA-3′) were designed and synthesized. All the shRNA fragments were inserted into the pFH-L lentiviral
vector (Shanghai Hollybio, Shanghai, China) containing green fluorescence protein (GFP) gene between NheI and PacI restriction sites. The
constructed plasmids were named as shICT1(S1), shICT1(S2), and
shCon, respectively.
Figure 2. Efficiency of ICT1 knockdown by lentivirus infection in the gastric cancer cells (A) Microscopic images of gastric cancer cells infected with lentivirus.
(B) Western blot analysis validated the knockdown efficiency of ICT1 in gastric cancer cells. (C) qPCR analysis of ICT1 knockdown efficiency in gastric cancer
cells. The mRNA expression of ICT1 was significantly suppressed when the cells were infected with shICT1(S1) and shICT1(S2). **P < 0.01 compared with
shCon. Scale bar, 10 μm.
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Packaging of lentivirus and cell infection
HEK293T cells were transfected with shICT1(S1), shICT1(S2), or
shCon, together with two helper plasmids, pVSVG-I and
pCMVΔR8.92 (Shanghai Hollybio) using Lipofectamine 2000
(Invitrogen, Carlsbad, USA) according to the manufacturer’s instructions. Three days after transfection, the culture supernatants were
harvested to extract lentiviruses expressing shICT1(S1), shICT1(S2)
or shCon. Then, lentiviruses were purified through ultracentrifugation and concentrated. For lentivirus infection, MGC80-3 and AGS
The role of ICT1 in gastric cancer cells
cells were cultured in six-well plates and lentiviruses were added at a
multiplicity of infection (MOI) of 60. After infection for 96 h, the
cells were collected and the infection efficiency was observed by
fluorescence microscopy (Olympus, Tokyo, Japan).
RNA extraction and quantitative RT-PCR analysis
Total RNA was extracted from MGC80-3 and AGS cells after 5 days of
lentivirus infection using the Trizol reagent (Carlsbad, San Diego, USA),
Figure 3. Knockdown of ICT1 inhibited the proliferation of gastric cancer cells (A) The growth of both shICT1(S1)-transfected and shICT1(S2)-transfected cells
were much slower than shCon-transfected cells. Values are expressed as the mean ± SD. ***P < 0.001 compared with shCon group. (B) Representative images
recorded under a fluorescence microscope, showing the size and the number of colonies in each group. (C) The number of colonies in the shICT1(S1) and
shICT1(S2) group was much smaller than that in the shCon group. Values are expressed as the mean ± SD. *P < 0.05, **P < 0.01, ***P < 0.001 compared with
the shCon group.
5
The role of ICT1 in gastric cancer cells
and then reverse transcribed into cDNA using M-MLV Reverse
Transcriptase (Promega, Madison, USA). Primers for qRT-PCR designed
for ICT1 sequence were as follows: ICT1-forward: 5′-CAGCCTGGA
CAAGCTCTACC-3′,
ICT1-reverse:
5′-GGAACCTGACTTCTG
CCTTG-3′. Actin (forward: 5′-GTGGACATCCGCAAAGAC-3′ and
reverse: 5′-AAAGGGTGTAACGCAACTA-3′) was used as an endogenous control. The gene-specific PCR amplification was performed on the
Bio-Rad Connet Real-Time PCR platform (Bio-Rad, Hercules, USA).
The reaction system for qRT-PCR was as follows: 10 μl 2 × SYBR premix ex taq, 0.5 μl primers (2.5 μM), 5 μl cDNA and 4.5 μl ddH2O. The
qRT-PCR reaction protocol included 1 min of initial denaturation at
95°C, and 40 cycles of denaturation at 95°C for 5 s, and annealing and
extension at 60°C for 20 s. The mRNA expression levels of ICT1 were
calculated using the comparative cycle using the 2−ΔΔCt method [15].
detection, the membranes were blocked in phosphate-buffered
saline (PBS) containing 0.05% Tween (PBST) and 5% nonfat milk
for 1 h at room temperature. Then the blots were probed with primary antibodies at 4°C overnight, followed by incubation with
HRP-conjugated goat anti-rabbit (SC-2054, 1:5000; Santa Cruz)
for 1 h at room temperature. GAPDH was used as an internal
standard. The primary antibodies used in this study included: anticyclin A2 (18202-1-AP, 1:1000; Cell Signaling, Boston, USA), anticyclin B1 (K0128-3, 1:1000; MEDICAL, Nagoya, Japan), anticaspase-3 (#9661, 1:500; Cell signaling), anti-PARP (#9542,
1:1000; Cell Signaling), anti-ICT1 (AP20382b, 1:1000, Abgent,
San Diego, USA), and anti-GAPDH (10494-1-AP, 1:50,000;
Proteintech, Chicago, USA).
Western blot analysis
MTT assay
After 7 days of infection, lentivirus-transfected MGC80-3 and AGS
cells were lysed with ice-cold 2 × SDS sample buffer (10 mM
EDTA, 100 mM Tris-HCl, pH 6.8, containing 4% SDS and 10%
Glycine). Total extracts were centrifuged (13,839 g, 15 min, 4°C)
and the protein concentration was determined using BCA protein
assay kit (Pierce, Washington, USA). Equal amounts of protein
(10 μg) were separated by 10% sodium dodecyl sulfatepolyacrylamide electrophoresis (SDS-PAGE) and transferred to
PVDF membranes (Millipore, Darmstadt, German). For immune
The proliferation of gastric cancer cells was determined by MTT
assay (Beyotime, Nanjing, China) according to the manufacturer’s
protocol. Briefly, MGC80-3 and AGS cells were seeded in 96-well
plates at a density of 2000 cells per well after 96 h lentiviral infection. MTT and acidic isopropanol (5% isopropanol, 10% SDS, and
10 mM HCl) were used as reagent to analyze the viable cell numbers
at daily intervals (1, 2, 3, 4, and 5 days). The absorbance of each
well was measured at the wavelength of 595 nm using a microplate
reader (Bio-Rad, Hercules, USA).
Figure 4. Knockdown of ICT1 blocked cell-cycle progression in MGC80-3 cells (A) FACS analysis of cell-cycle distribution in MGC80-3 cells after shICT1(S1)
transfection. (B) Downregulation of ICT1 caused an increase of MGC80-3 cells in G2/M phase and a concomitant decrease of cells in G0/G1 phase and S phase.
(C) Knockdown of ICT1 led to an increase of MGC80-3 cells in sub-G1 phase. (D) Effect of ICT1 downregulation on cell-cycle regulators. Western blot analysis of
the expressions of cyclin A2 and cyclin B1 in MGC80-3 cells after shICT1(S1) transfection. Data are expressed as the mean ± SD. ***P < 0.001 compared with
the shCon group.
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Colony formation assay
Cells (400 cells per well) were seeded in a six-well plate after 5 days
of lentivirus infection. Cells were cultured in complete medium
RPMI 1640 supplemented with 10% FBS (Biowest) for 8 days.
Then cells were fixed with PBS containing 4% paraformaldehyde
for 30 min at room temperature, stained with crystal violet. After
20 min of incubation, cells were gently washed and air-dried. The
number of colonies (>50 cells per colony) was counted under a
microscope (Olympus, Tokyo, Japan).
Cell-cycle and apoptosis analysis by flow cytometry
Cells were inoculated into 6-cm dishes at a density of 2 × 105 cells
per dish for cell-cycle test and 80,000 cells per dish for apoptosis
analysis after 40 h of lentivirus infection. Propidium iodide (PI) and
Annexin V/7AAD were used to stain the cells according to the manufacturer’s instructions. FAC Scan flow cytometry (Becton
Dickinson, San Jose, USA) was then performed to measure the
change of cell-cycle and the percentage of apoptotic cells.
Statistical analysis
All experiments were repeated at least for three times. All data were
analyzed using GraphPad Prism software and expressed as the mean ±
standard deviation (SD) from three independent experiments.
The role of ICT1 in gastric cancer cells
Statistical differences between groups were determined using Student’s
t-test. P < 0.05 was defined as a significant difference.
Results
ICT1 is overexpressed in gastric cancer
ICT1 mRNA levels in human gastric cancer tissues were investigated by
using DErrico Gastric (GEO ID: 204868_at) and Cho Gastric data
(GEO ID: ILMN_2182198) in Oncomine database (www.oncomine.
org). A total of 69 tissues from patients, including 31 paired gastric carcinoma and adjacent normal gastric mucosa and seven unmatched gastric carcinoma samples, were analyzed in DErrico Gastric. A total of 90
tissues, 65 gastric adenocarcinoma, 19 paired surrounding normal tissue, and 6 gastrointestinal stromal tumor samples, were analyzed in
ChoGastric data. As shown in Fig. 1, ICT1 mRNA expression was significantly elevated in human gastric cancer tissues, including gastric
intestinal type adenocarcinoma, diffuse gastric adenocarcinoma, gastric
mixed adenocarcinoma, and microsatellite stable/instable gastric adenocarcinoma, compared with that in normal tissues, which suggested that
ICT1 was highly expressed in gastric cancer in DErrico Gastric data;
meanwhile, in Cho Gastric data, ICT1 had a significant higher expression in gastric mixed adenocarcinoma than that in normal tissues.
Collectively, ICT1 had a higher expression in gastric tissues than in normal tissues and had a clinical significance in gastric cancer.
Figure 5. Knockdown of ICT1 blocked cell-cycle progression in AGS cells (A) FACS analysis of cell-cycle distribution in AGS cells after shICT1(S1) transfection.
(B) Downregulation of ICT1 caused an increase of AGS cells in the G2/M phase and G0/G1 phase and a concomitant decrease of cells in the S phase. (C)
Knockdown of ICT1 led to an increase of AGS cells in the sub-G1 phase. (D) Effect of ICT1 downregulation on cell-cycle regulators. Western blot analysis of the
expressions of cyclin A2 and cyclin B1 in AGS cells after shICT1(S1) transfection. Data are expressed as the mean ± SD. **P < 0.01, ***P < 0.001 compared
with the shCon group.
The role of ICT1 in gastric cancer cells
Lentivirus-mediated shRNA suppressed ICT1
expression in gastric cancer cells
To investigate the potential role of ICT1 in gastric cancer, the
expression of ICT1 was silenced by lentivirus-mediated shRNA.
As shown in Fig. 2A, more than 80% of MGC80-3 and AGS cells
were GFP positive in shICT1(S1) and shICT1(S2) groups as
revealed by fluorescence microscopy, indicating high infection
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efficiency. Moreover, RT-PCR and western blot analysis were
performed to confirm ICT1 expression. As shown in Fig. 2B,C,
the mRNA and protein levels of ICT1 in both shICT1(S1)- and
shICT1(S2)-infected cells were significantly decreased compared
that in shCon-infected cells (P < 0.01). These results showed that
the designed ICT1 shRNAs could effectively down-regulate ICT1
expression.
Figure 6. Knockdown of ICT1-induced cell apoptosis in gastric cancer cells (A) Cytogram of Annexin V-APC binding versus PI uptake after shICT1 (S1) transfection. (B) Downregulation of ICT1 led to an increase of apoptotic cells. (C) Knockdown of ICT1 altered the protein levels of apoptotic markers, including cleaved
caspase-3 and PARP, as determined by western blot analysis. Data are expressed as the mean ± SD. *P < 0.05, **P < 0.01, and ***P < 0.001 compared with the
shCon group.
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Knockdown of ICT1 repressed cell proliferation
of gastric cancer cells
To better understand the role of ICT1 in the gastric cancer tumorigenesis, we determined the effect of ICT1 knockdown on the proliferation of MGC80-3 and AGS cells by MTT assay for 5 days. As
shown in Fig. 3A, the growths of MGC80-3 and AGS cells were significantly decreased in the shICT1(S1) and shICT1(S2) infection
groups in a time-dependent manner when compared with that in the
shCon group. In addition, we evaluated the colony formation capacity in MGC80-3 cells with three different treatments: shCon,
shICT1(S1), and shICT1(S2), and the colony formation capacity in
AGS cells with two different groups: shCon and shICT1(S1).
Consistent with results of MTT analysis, downregulation of ICT1
significantly suppressed colony formation capability of MGC80-3
cells. It was found that there was smaller colonies and fewer colony
numbers in shICT1(S1) (P < 0.01) and shICT1(S2) (P < 0.05) than
those in shCon (Fig. 3B,C). A similar tendency was also found in
AGS cells infected with shICT1(S1) (Fig. 3B,C, P < 0.001).
Collectively, knockdown of ICT1 by RNAi could markedly suppress
the proliferation and colony formation ability of MGC80-3 and
AGS cells.
Knockdown of ICT1-induced cell-cycle arrest in gastric
cancer cells
To investigate the potential mechanism of cell growth inhibition in
MGC80-3 and AGS cells by ICT1 knockdown, flow cytometry was
performed to determine the cell-cycle distribution (Figs. 4 and 5).
Obviously, the percentage of cells at G2/M phase was significantly
increased in the shICT1(S1) group in MGC80-3 cells, with 20.2%
in the shCon group and 50.4% in the shICT1(S1) group, which suggested that MGC80-3 cells were arrested in the G2/M phase
(Fig. 4B, P < 0.001). AGS cells were also arrested at G2/M phase
after ICT1 silencing (Fig. 5B, P < 0.01). To further reveal the mechanism underlying the cell-cycle arrest, the expressions of some cellcycle markers were detected. As shown in Figs. 4D and 5D, the
The role of ICT1 in gastric cancer cells
expression levels of cyclin A2 and cyclin B1 which are associated
with G2-M transition were decreased in the shICT1(S1) group of
both MGC80-3 cells and AGS cells. Collectively, knockdown of
ICT1 may mediate cell-cycle arrest most probably through a cyclindependent manner in gastric cancer cells.
In addition, more cells were accumulated in the sub-G1 phase,
which represents apoptotic cells, after ICT1 knockdown in both
MGC80-3 cells (Fig. 4C, P < 0.001) and AGS cells (Fig. 5C, P <
0.01).
Knockdown of ICT1-induced apoptosis in gastric cancer
cells
To further investigate whether ICT1 silencing causes any apoptosis
in gastric cancer cells, Annexin V/7AAD double staining was applied
to determine apoptosis. As shown in Fig. 6A,B, knockdown of ICT1
with shICT1(S1) significantly increased apoptosis compared with
the shCon group in AGS cells (P < 0.05 for early apoptosis) and in
MGC80-3 cells (P < 0.001 for late apoptosis). Furthermore, the
expressions of several apoptotic markers were determined by western blot analysis. As shown in Fig. 6C, the expression levels of
cleaved caspase-3 and PARP were up-regulated in gastric cancer
cells after ICT1 silencing. Thus, knockdown of ICT1 could significantly induce apoptotic effect via activating PARP in gastric cancer
cells.
Discussion
Recently ICT1 has been proved to be involved in various kinds of
tumor progression. However, its role in gastric cancer has been
poorly characterized. In the present study, we first identified ICT1 as
a novel molecule that can drive gastric cancer progression by
Oncomine data analysis. Then we designed two different
ICT1 shRNAs to specifically block its endogenous expression in
human gastric cancer cell lines MGC80-3 and AGS. The pathway
by which ICT1 mediates cell-cycle arrest and apoptosis can be summarized as Fig. 7. Knockdown of ICT1 can arrest cell-cycle at G2/M
Figure 7. The proposed mechanism by which ICT1 mediates cell-cycle arrest and apoptosis
The role of ICT1 in gastric cancer cells
via cyclin-dependent pathway and promote apoptosis through activating PARP in human gastric cancer cells. This result is similar to
Wang’s study conducted in prostate cancer cell lines [13]. This phenomenon demonstrated that ICT1 may affect the proliferation of different cancers in the same mode. Different from Wang’s study, our
study focused on the effect of ICT1 in patient tissues, which provided
a more convincible proof to demonstrate the effect of ICT1 on gastric
cancer cell proliferation.
Previous studies have indicated that depletion of ICT1 inhibits
cell proliferation in HeLa cells, which is ascribed to cell-cycle arrest
and cell apoptosis [16]. In our cell-cycle analysis results, ICT1-
9
silenced cells were mostly arrested in the G2/M phase compared to
controls. This effect may be associated with alterations in the
expression of cyclins, such as cyclin A2 and cyclin B1. Cyclins are
activators of specific serine/threonine protein kinases and can promote cell-cycle process. Cyclin A2 is overexpressed in many cancers
[17] and its overexpression could promote G2/M phase transition
[18] to enhance cell proliferation [19]. Cyclin B1 is an M phase promoting factor and has been demonstrated to be essential for the initiation of mitosis [20,21]. Western blot analysis showed that the
expression levels of cyclin A2 and cyclin B1 were decreased in
ICT1-silenced cells. Thus, it is reasonable to infer that knockdown
Figure 8. High ICTI expression level is correlated with poor survival in different cancer patients (A) Breast cancer data from GSE1456_U133A database. (B)
Breast cancer data from NKI database. (C) Renal cancer data from TCGA-KIRC database (HR: 1.52). (D) Renal cancer data from TCGA-KIRC database (HR: 2.1).
(E) Lung cancer data from GES4573 database. (F) Skin cancer data from GES19234 database.
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of ICT1 may induce cell-cycle arrest at G2/M phase most probably
through the suppression of cyclin A2 and cyclin B1.
To further explore the mechanisms involved in inhibition of proliferation by ICT1 silencing, flow cytometry was used to investigate
the apoptosis after ICT1 knockdown. Annexin V/7AAD double
staining showed knockdown of ICT1 significantly promoted apoptosis in human gastric cancer cells. Moreover, the expressions of
cleaved caspase-3 and PARP were obviously increased in ICT1silenced cells. Apoptosis is a process of programmed cell death,
which plays a crucial role in keeping balance of cell proliferation
[21]. Caspase-cascade, as a central part of cell apoptosis, could be
regulated by various kinds of molecules and activated through
mitochondrion-dependent pathways [22,23]. In addition, ICT1 has
been identified as a mitochondrial release factor family member.
Downregulation of ICT1 may impair mitochondrial function via
caspase-cascade cell apoptosis pathway. These results are supported
by previous studies, which demonstrated that knockdown of ICT1
in prostate cancer cells and HeLa cells could inhibit cell proliferation
due to apoptotic cell death [10,13].
It is widely accepted that aberrant expression of oncogene and
antioncogene may affect the clinical outcome of patients. Hence, it
is necessary to study whether ICT1 level is linked to the prognosis
of gastric cancer patients. Unfortunately, we are unable to acquire
enough clinical cases and database concerning the effect of ICT1 on
the prognosis of gastric cancer patients in the Oncomine database.
However, data on the relationship between ICT1 and prognosis in
breast cancer patients, lung cancer patients, renal cancer patients,
and skin cancer patients are available in the Oncomine database.
According to these data, we performed a Kaplan–Meier survival
analysis. The results revealed that high ICT1 mRNA levels are significantly correlated with poor prognosis (Fig. 8). Based on these
results, it is reasonable for us to propose that ICT1 expression level
may affect clinical outcome of gastric cancer patients. An in-depth
mechanistic study is needed to evaluate whether ICT1 can be used
as a novel prognostic marker in gastric cancer patients.
In summary, our results demonstrated that knockdown of ICT1
inhibited cell viability and colony formation ability of gastric cells,
induced cell-cycle arrest at G2/M phase via a cyclin-dependent pathway, and promoted apoptosis via a caspase-dependent pathway.
Our study highlights the crucial role of ICT1 in gastric cancer cell
proliferation. However, more investigations are needed to illuminate
the exact molecular mechanism of the role of ICT1 in the treatment
of gastric cancer.
Funding
This work was supported by a grant from the Natural Science
Foundation of Anhui Province (No. 1508085MH146).
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