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<front>
<journal-meta>
<journal-id journal-id-type="pmc">Biocell</journal-id>
<journal-id journal-id-type="nlm-ta">Biocell</journal-id>
<journal-id journal-id-type="publisher-id">Biocell</journal-id>
<journal-title-group>
<journal-title>Biocell</journal-title>
</journal-title-group>
<issn pub-type="epub">1667-5746</issn>
<issn pub-type="ppub">0327-9545</issn>
<publisher>
<publisher-name>Tech Science Press</publisher-name>
<publisher-loc>USA</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="publisher-id">10119</article-id>
<article-id pub-id-type="doi">10.32604/biocell.2021.010119</article-id>
<article-categories>
<subj-group subj-group-type="heading">
<subject>Article</subject>
</subj-group>
</article-categories>
<title-group>
<article-title>The <italic>F5</italic> gene predicts poor prognosis of patients with gastric cancer by promoting cell migration identified using a weighted gene co-expression network analysis</article-title><alt-title alt-title-type="left-running-head">The <italic>F5</italic> gene predicts poor prognosis of patients with gastric cancer by promoting cell migration identified using a weighted gene co-expression network analysis</alt-title><alt-title alt-title-type="right-running-head">The <italic>F5</italic> gene predicts poor prognosis of patients with gastric cancer by promoting cell migration identified using a weighted gene co-expression network analysis</alt-title>
</title-group>
<contrib-group content-type="authors">
<contrib id="author-1" contrib-type="author" equal-contrib="yes">
<name name-style="western">
<surname>Tang</surname>
<given-names>Mengyi</given-names>
</name>
<xref ref-type="aff" rid="aff-1">1</xref>
<xref ref-type="aff" rid="aff-2">2</xref>
<xref ref-type="aff" rid="aff-3">3</xref>
<xref ref-type="aff" rid="aff-4">4</xref>
</contrib>
<contrib id="author-2" contrib-type="author" equal-contrib="yes">
<name name-style="western">
<surname>Yang</surname>
<given-names>Bowen</given-names>
</name>
<xref ref-type="aff" rid="aff-1">1</xref>
<xref ref-type="aff" rid="aff-2">2</xref>
<xref ref-type="aff" rid="aff-3">3</xref>
<xref ref-type="aff" rid="aff-4">4</xref>
</contrib>
<contrib id="author-3" contrib-type="author">
<name name-style="western">
<surname>Zhang</surname>
<given-names>Chuang</given-names>
</name>
<xref ref-type="aff" rid="aff-1">1</xref>
<xref ref-type="aff" rid="aff-2">2</xref>
<xref ref-type="aff" rid="aff-3">3</xref>
<xref ref-type="aff" rid="aff-4">4</xref>
</contrib>
<contrib id="author-4" contrib-type="author">
<name name-style="western">
<surname>Zhang</surname>
<given-names>Chaoxu</given-names>
</name>
<xref ref-type="aff" rid="aff-1">1</xref>
<xref ref-type="aff" rid="aff-2">2</xref>
<xref ref-type="aff" rid="aff-3">3</xref>
<xref ref-type="aff" rid="aff-4">4</xref>
</contrib>
<contrib id="author-5" contrib-type="author">
<name name-style="western">
<surname>Zang</surname>
<given-names>Dan</given-names>
</name>
<xref ref-type="aff" rid="aff-1">1</xref>
<xref ref-type="aff" rid="aff-2">2</xref>
<xref ref-type="aff" rid="aff-3">3</xref>
<xref ref-type="aff" rid="aff-4">4</xref>
</contrib>
<contrib id="author-6" contrib-type="author">
<name name-style="western">
<surname>Gong</surname>
<given-names>Libao</given-names>
</name>
<xref ref-type="aff" rid="aff-1">1</xref>
<xref ref-type="aff" rid="aff-2">2</xref>
<xref ref-type="aff" rid="aff-3">3</xref>
<xref ref-type="aff" rid="aff-4">4</xref>
</contrib>
<contrib id="author-7" contrib-type="author">
<name name-style="western">
<surname>Liu</surname>
<given-names>Yunpeng</given-names>
</name>
<xref ref-type="aff" rid="aff-1">1</xref>
<xref ref-type="aff" rid="aff-2">2</xref>
<xref ref-type="aff" rid="aff-3">3</xref>
<xref ref-type="aff" rid="aff-4">4</xref>
</contrib>
<contrib id="author-8" contrib-type="author" corresp="yes">
<name name-style="western">
<surname>Li</surname>
<given-names>Zhi</given-names>
</name>
<xref ref-type="aff" rid="aff-1">1</xref>
<xref ref-type="aff" rid="aff-2">2</xref>
<xref ref-type="aff" rid="aff-3">3</xref>
<xref ref-type="aff" rid="aff-4">4</xref><email>zli@cmu.edu.cn</email>
</contrib>
<contrib id="author-9" contrib-type="author" corresp="yes">
<name name-style="western">
<surname>Qu</surname>
<given-names>Xiujuan</given-names>
</name>
<xref ref-type="aff" rid="aff-1">1</xref>
<xref ref-type="aff" rid="aff-2">2</xref>
<xref ref-type="aff" rid="aff-3">3</xref>
<xref ref-type="aff" rid="aff-4">4</xref><email>xiujuanqu@yahoo.com</email>
</contrib>
<aff id="aff-1">
<label>1</label><institution>Department of Medical Oncology, The First Hospital of China Medical University</institution>, <addr-line>Shenyang</addr-line>, <country>China</country></aff>
<aff id="aff-2">
<label>2</label><institution>Key Laboratory of Anticancer Drugs and Biotherapy of Liaoning Province, The First Hospital of China Medical University</institution>, <addr-line>Shenyang</addr-line>, <country>China</country></aff>
<aff id="aff-3">
<label>3</label><institution>Liaoning Province Clinical Research Center for Cancer</institution>, <addr-line>Shenyang</addr-line>, <country>China</country></aff>
<aff id="aff-4">
<label>4</label><institution>Key Laboratory of Precision Diagnosis and Treatment of Gastrointestinal Tumors, Ministry of Education</institution>, <addr-line>Shenyang</addr-line>, <country>China</country></aff>
</contrib-group><author-notes><corresp id="cor1">&#x002A;Address correspondence to: Zhi Li, <email>zli@cmu.edu.cn</email>; Xiujuan Qu, <email>xiujuanqu@yahoo.com</email></corresp></author-notes>
<pub-date pub-type="epub" date-type="pub" iso-8601-date="2021-06-05">
<day>05</day>
<month>06</month>
<year iso-8601-date="2021">2021</year>
</pub-date>
<volume>45</volume>
<issue>4</issue>
<fpage>911</fpage>
<lpage>921</lpage>
<history>
<date date-type="received">
<day>12</day>
<month>2</month>
<year iso-8601-date="2020">2020</year>
</date>
<date date-type="accepted">
<day>18</day>
<month>5</month>
<year iso-8601-date="2020">2020</year>
</date>
</history>
<permissions>
<copyright-statement>&#x00A9; 2021 Tang et al.</copyright-statement>
<copyright-year>2021</copyright-year>
<copyright-holder>Tang et al.</copyright-holder>
<license xlink:href="https://creativecommons.org/licenses/by/4.0/">
<license-p>This work is licensed under a <ext-link ext-link-type="uri" xlink:type="simple" xlink:href="https://creativecommons.org/licenses/by/4.0/">Creative Commons Attribution 4.0 International License</ext-link>, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.</license-p>
</license>
</permissions>
<self-uri content-type="pdf" xlink:href="TSP_BIOCELL_10119.pdf"></self-uri>
<abstract>
<p>Distal gastric cancer (DGC) is a subgroup of gastric cancer (GC), which has different molecular characteristics from proximal gastric cancer (PGC). These differences result in different overall survival (OS) rates; however, data pertaining to the survival rate in PGC or DGC are contradictory. This suggests that the location of GC is not the unique cause of the different survival rates, while the molecular characteristics might be more important factors determining the prognosis of DGC. Therefore, the aim of this study was to discover key prognostic factors in DGC using bioinformatic methods and to explore the potential molecular mechanism. The Cancer Genome Atlas (TCGA) public database was employed to screen data relating to DGC, and we conducted a weighted gene co-expression network analysis (WGCNA) on DGC patient samples to establish co-expression modules. High-weight genes (hub genes) in a dominant color module were identified. <italic>In vitro</italic> experiments and gene set enrichment analyses (GSEA) were carried out to elucidate the potential molecular mechanism. In this study, 139 DGC samples were enrolled to perform a co-expression analysis. According to the correlation between gene modules and clinical characteristics, the royal blue module related to stage M of DGC was screened, and a survival analysis was conducted to show that high-coagulation-factor V (<italic>F5</italic>) expression was related to the short OS of patients with GC. <italic>In vitro</italic> experiments confirmed that <italic>F5</italic> could promote the migration of GC cells. GSEA suggested that <italic>F5</italic> might have affected the prognosis of GC by modulating the activities of the Wnt and/or the TGF-&#x03B2; signaling pathways. Our results indicated that high <italic>F5</italic> expression predicts poor prognosis of patients with DGC, and it functions probably by promoting cell migration through the Wnt and/or the TGF-&#x03B2; signaling pathways.</p>
</abstract>
<kwd-group kwd-group-type="author">
<kwd>Distal gastric cancer</kwd>
<kwd>WGCNA</kwd>
<kwd><italic>F5</italic></kwd>
<kwd>Cell migration</kwd>
<kwd>Poor prognosis</kwd>
</kwd-group>
</article-meta>
</front>
<body>
<sec id="s1">
<title>Introduction</title>
<p>Gastric cancer (GC) is a high-risk tumor with the highest mortality and morbidity rates worldwide. GC is often diagnosed at an advanced stage when patients have a median overall survival (mOS) of about 10&#x2013;12 months. According to the location of the disease, GC can be divided into proximal gastric cancer (PGC), middle stomach cancer, and distal gastric cancer (DGC). Epidemiological studies have shown that the biological and pathological characteristics of DGC are different from PGC (<xref ref-type="bibr" rid="ref-34">Devesa <italic>et al</italic>., 1998</xref>). For example, DGC tends to have poorly differentiated tumors compared with PGC, and DGC is associated with more advanced tumor stage and older age compared with PGC (<xref ref-type="bibr" rid="ref-27">Wang <italic>et al</italic>., 2019</xref>). Different biological and pathological characteristics result in different overall survival (OS) rates. However, the data pertaining to rates of survival of DGC or PGC are contradictory. A study (<xref ref-type="bibr" rid="ref-6">Higuchi <italic>et al</italic>., 2004</xref>) has reported shorter survival in patients with DGC compared to those with PGC, while some reports (<xref ref-type="bibr" rid="ref-19">Pacelli <italic>et al</italic>., 2001</xref>; <xref ref-type="bibr" rid="ref-20">Petrelli <italic>et al</italic>., 2017</xref>; <xref ref-type="bibr" rid="ref-29">Yu <italic>et al</italic>., 2018</xref>) have shown longer overall survival (OS) in DGC patients. Even though, another study (<xref ref-type="bibr" rid="ref-4">Costa <italic>et al</italic>., 2016</xref>) has shown no obvious difference in the prognosis of DGC and PGC. Therefore, the location of GC is not the unique cause of the different survival rates. Investigation of the molecular characteristics might be more important, which may be one of the decisive factors determining clinical biological behavior and prognosis of DGC.</p>
<p>Currently, the molecular mechanism that underlies the development of GC remains to be fully elucidated. A study has shown that cell invasion and migration in GC can be promoted by homeobox C10 (HOXC10) through the upregulation of pro-inflammatory cytokines (<xref ref-type="bibr" rid="ref-15">Li <italic>et al</italic>., 2020</xref>). Moreover, proliferation and migration in GC could be promoted via activation of the Wnt signaling pathway by LncRNA HLA complex group 11 (HCG11) (<xref ref-type="bibr" rid="ref-30">Zhang <italic>et al</italic>., 2019</xref>). However, there are no reports on the biomarkers related to DGC.</p>
<p>Weighted gene co-expression network analysis (WGCNA) is an approach used in the co-expression module correlation analysis from microarray samples (<xref ref-type="bibr" rid="ref-14">Langfelder and Horvath, 2008</xref>). WGCNA has been used in various biological scenarios and is useful in the exploration of therapeutic targets or potential biomarkers (<xref ref-type="bibr" rid="ref-10">Ivliev <italic>et al</italic>., 2010</xref>).</p>
<p>In this study, we aimed to reveal potential molecular mechanisms leading to the development of DGC using WGCNA. Our results suggested that high-coagulation-factor V (<italic>F5</italic>) expression results in a poor prognosis of patients with DGC by promoting cell migration, and which might function by regulating the Wnt and/or the TGF-&#x03B2; signaling pathways.</p>
</sec>
<sec id="s2">
<title>Materials and Methods</title>
<sec id="s2_1">
<title>Data source and data processing</title>
<sec id="s2_1_1">
<title>Data processing</title>
<p>RNA-sequencing data of gastric cancer samples and relevant clinical data were downloaded from the database of TCGA (<uri xlink:href="http://cancergenome.nih.gov/">http://cancergenome.nih.gov/</uri>). It was used as data to perform our study.</p>
</sec>
<sec id="s2_1_2">
<title>Data inclusion and exclusion criteria</title>
<p>(1) Data which was at least 18 years of age were eligible for enrollment; (2) The sample must have been pathologically confirmed as gastric cancer; (3) The gastric cancer data in TCGA contains six aspects: Gastroesophageal Junction, Cardia/Proximal, Fundus/Body, Antrum/Distal, Stomach (NOS) and Other (please specify). We chose the &#x201C;Antrum/Distal&#x201D; part as DGC to perform our study.</p>
</sec>
<sec id="s2_1_3">
<title>Gene selection</title>
<p>For the selected distal gastric cancer data, the genes were sorted by the median absolute deviation variance size, and the front 3600 genes were extracted. The clinical characteristics of the sample contained nine aspects: histological grade, stage T, stage N, stage M, gender, race, tumor stage, age, and morphology.</p>
</sec>
<sec id="s2_1_4">
<title>Construction of co-expression network</title>
<p>WGCNA package was used to build a co-expression network (139 samples of DGC were used) in R after the 3600 most variant genes were tested. The adjacency matrix A<sub>mn</sub> was defined, and the soft-thresholding parameter <italic>&#x03B2;</italic> &#x003D; 4 was chosen. Then, we constructed the topological overlap matrix (TOM) to counter the effects of missing or spurious connections between network nodes.</p>
<p><disp-formula id="eqn-1">
<!--<alternatives><graphic mimetype="image" mime-subtype="png" xlink:href="eqn-1.png"/>--><!--<tex-math id="tex-eqn-1"><![CDATA[TO{M_{m,n}} = \; \displaystyle{{\mathop \sum \nolimits_{k = 1}^N {A_{m,k}}.{A_{k,n}} + \; {A_{m,n}}} \over {\mathop {\min }\limits_\; \left( {{K_m},{K_n}} \right) + 1 - \; {A_{m,n}}}}]]></tex-math>--><mml:math id="mml-eqn-1" display="block"><mml:mi>T</mml:mi><mml:mi>O</mml:mi><mml:mrow><mml:msub><mml:mi>M</mml:mi><mml:mrow><mml:mi>m</mml:mi><mml:mo>,</mml:mo><mml:mi>n</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mo>&#x003D;</mml:mo><mml:mspace width="thickmathspace"></mml:mspace><mml:mstyle scriptlevel="0" displaystyle="true"><mml:mrow><mml:mfrac><mml:mrow><mml:msubsup><mml:mrow><mml:mo movablelimits="false">&#x2211;</mml:mo></mml:mrow><mml:mrow><mml:mi>k</mml:mi><mml:mo>&#x003D;</mml:mo><mml:mn>1</mml:mn></mml:mrow><mml:mi>N</mml:mi></mml:msubsup><mml:mo>&#x2061;</mml:mo><mml:mrow><mml:msub><mml:mi>A</mml:mi><mml:mrow><mml:mi>m</mml:mi><mml:mo>,</mml:mo><mml:mi>k</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mo>.</mml:mo><mml:mrow><mml:msub><mml:mi>A</mml:mi><mml:mrow><mml:mi>k</mml:mi><mml:mo>,</mml:mo><mml:mi>n</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mo>&#x002B;</mml:mo><mml:mspace width="thickmathspace"></mml:mspace><mml:mrow><mml:msub><mml:mi>A</mml:mi><mml:mrow><mml:mi>m</mml:mi><mml:mo>,</mml:mo><mml:mi>n</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:mrow><mml:mrow><mml:munder><mml:mrow><mml:mo form="prefix">min</mml:mo></mml:mrow><mml:mspace width="thickmathspace"></mml:mspace></mml:munder><mml:mo>&#x2061;</mml:mo><mml:mrow><mml:mo>(</mml:mo><mml:mrow><mml:mrow><mml:msub><mml:mi>K</mml:mi><mml:mi>m</mml:mi></mml:msub></mml:mrow><mml:mo>,</mml:mo><mml:mrow><mml:msub><mml:mi>K</mml:mi><mml:mi>n</mml:mi></mml:msub></mml:mrow></mml:mrow><mml:mo>)</mml:mo></mml:mrow><mml:mo>&#x002B;</mml:mo><mml:mn>1</mml:mn><mml:mo>&#x2212;</mml:mo><mml:mspace width="thickmathspace"></mml:mspace><mml:mrow><mml:msub><mml:mi>A</mml:mi><mml:mrow><mml:mi>m</mml:mi><mml:mo>,</mml:mo><mml:mi>n</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:mrow></mml:mfrac></mml:mrow></mml:mstyle></mml:math>
<!--</alternatives>--></disp-formula></p>
<p>Next, the average linkage hierarchical clustering was conducted to classify genes into gene modules with high absolute correlations. The minimum size was 30.</p>
</sec>
<sec id="s2_1_5">
<title>Correlation between clinical characteristics and different modules</title>
<p>With the purpose to identify modules associated with clinical characteristics (distal gastric cancer), the correlation between clinical characteristics and module eigengenes was calculated by the Spearman correlation analysis and a <italic>p</italic>-value of &#x003C;0.05 as statistically significant. Meanwhile, we tested the module significance defined as the average gene significance of each gene in the linear regression between the clinical characteristics and gene expression. In general, the correlation between clinical characteristics and module eigengenes tended to be related to the module significance.</p>
</sec>
<sec id="s2_1_6">
<title>Identification of hub genes</title>
<p>Genes within the co-expression module are highly connected and have similar effects. The hub genes we filtered in each module based on the connectivity within the module and the correlation with the module&#x2019;s characteristic genes. The cytoHubba plugin was used to extract the hub genes in every module with the purpose of obtaining a balance between the core genes and avoid missing any key gene based on Cytoscape (<xref ref-type="bibr" rid="ref-2">Chin <italic>et al</italic>., 2014</xref>).</p>
</sec>
<sec id="s2_1_7">
<title>Survival analysis</title>
<p>With the purpose to evaluate each hub gene as a prognostic marker of distal gastric cancer, we conducted survival analyses. We divided DGC samples into 2 groups based on the median expression values of the gene. The R package &#x201C;survival&#x201D; was used to create K-M survival curves to assess the prognostic value, and the log-rank test was used to evaluate differences between groups. After this, the <italic>p</italic>-values were produced. On the other hand, the prognostic value of hub gene expression in GC was analyzed again by using Kaplan&#x2013;Meier Plotter on-line database (<uri xlink:href="https://kmplot.com/analysis/">https://kmplot.com/analysis/</uri>).</p>
</sec>
<sec id="s2_1_8">
<title>Differential expression of hub genes and PPI network constructions</title>
<p>The on-line database Gene Expression Profiling Interactive Analysis (GEPIA) (<uri xlink:href="http://gepia.cancer-pku.cn">http://gepia.cancer-pku.cn</uri>) was used to identify the differential expression of target molecules between the gastric cancer tissue and gastric tissue. GEPIA is an interactive web that includes 8587 normal and 9736 tumors samples from TCGA and the GTEx projects (<xref ref-type="bibr" rid="ref-22">Tang <italic>et al</italic>., 2017</xref>). Besides, the Protein-Protein Interaction (PPI) Network Construction was performed using the STRING web (<uri xlink:href="https://string-db.org/cgi/input.pl">https://string-db.org/cgi/input.pl</uri>) method to analyze the function of the protein encoded by the target gene.</p>
</sec>
</sec>
<sec id="s2_2">
<title>Cytological experiments verify the effect of selected hub genes on gastric cancer cells</title>
<sec id="s2_2_1">
<title>Cell culture and transfection</title>
<p>We obtained GC cells lines MGC803, BGC823, SGC7901 and HGC27 from the Type Culture Collection of the Chinese Academy of Sciences (Shanghai, China), which were cultured with RPMI-1640 medium containing 10% heat-inactivated fetal bovine serum (FBS) and 1% penicillin-streptomycin. They were cultured in a humidified incubator at 37&#x00B0;C containing 5% CO<sub>2</sub>, digested, and passaged with 0.25% trypsin digest, and passaged once every 2&#x2013;3 days. We used logarithmic growth phase cells in all experiments.</p>
<p>The specific siRNAs targeted to <italic>F5</italic> and corresponding negative control (NC), were compounded by RiboBio (Guangzhou, China). SGC7901 cells (2 &#x00D7; 10<sup>5</sup>) were transfected with siRNAs Lipofectamine 2000 reagent (Invitrogen) Transfection&#x2002;Reagent based on the manufacturer&#x2019;s instructions.</p>
</sec>
<sec id="s2_2_2">
<title>RT-qPCR detection of mRNA expression levels</title>
<p>Total RNA was isolated with Trizol reagent (Invitrogen, USA) and quantified by measuring the absorbance at 260 nm by nanodrop 2000 (Thermo Fisher Scientific, USA). For mRNA detection, we used the One Step PrimeScript mRNA cDNA Synthesis Kit (Takara, Japan) to carry out reverse transcription. SYBR Premix EX Taq<sup>TM</sup> II (Perfect Real Time) (Takara, Japan) was used to generate cDNA from 1000 ng total RNA. The Applied Biosystems 7500 Real-Time PCR Systems (Thermo Fisher Scientific, Waltham, MA, USA) was used to run the RT-qPCR. The conditions of PCR were 30 s at 95&#x00B0;C, followed by 45 cycles at 95&#x00B0;C for 5 s, and at 58&#x00B0;C for 25 s. The Applied Biosystems 7500 software program (version 2.3) was used to analyze the data. The fold change of the RNA expression was calculated by the 2<sup>&#x2212;&#x0394;&#x0394;Ct</sup> method.</p>
<p>The PCR primers used are as follows:</p>
<p><italic>F5</italic>: Forward (5&#x2019;-ACCACAATCTACCATTTCAGGAC-3&#x2019;) and Reverse (5&#x2019;-CTTCTCCGCAGGGAATGTGT-3&#x2019;).</p>
<p>18S: Forward (5&#x2019;-CCCGGGGAGGTAGTGACGAAAAAT-3&#x2019;) and Reverse (5&#x2019;-CGCCCGCCCGCTCCCAAGAT-3&#x2019;).</p>
</sec>
<sec id="s2_2_3">
<title>Cell viability assays</title>
<p>Cell viability was determined using MTT assay. Briefly, the 96-well plates with a cell density of 4 &#x00D7; 10<sup>3</sup> cells/well for 72 h were used to incubate SGC7901 cells, which were transfected with the <italic>F5</italic> siRNA or NC siRNA. After treatment of cells with various conditions, the medium was removed, and 20 &#x03BC;L of MTT (5 mg/mL; Sigma Chemical Co., St Louis, MO, USA) was added to each well for 4 h incubation at 37&#x00B0;C. Then 200 &#x03BC;L of DMSO was added to each well. After shaking for 5 min, a microplate reader (model 550; Bio-Rad Laboratories, Inc., Hercules, CA, USA) was used to measure the absorbance at 570 nm.</p>
</sec>
<sec id="s2_2_4">
<title>Transwell migration assay</title>
<p>We carried out the migration assays in a 24-well chamber and used 8-&#x03BC;m pore size membranes (Corning, USA) to inserted polycarbonate. For migration assay, 3 &#x00D7; 10<sup>4</sup> cells were plated within 200 &#x03BC;L serum-free medium onto the upper chamber, and 500 &#x03BC;L medium with 2.5% FBS was added to the lower chamber. After incubating for 24 h, the chambers were fixed with methanol and then stained with 0.1% Wright-Giemsa dye. We captured 5 different fields and counted at 20X magnification per well. Fluorescence microscopy (BX53, Olympus, Japan) was used to visualize the cells. Each experiment was carried out at least three times.</p>
</sec>
<sec id="s2_2_5">
<title>GSEA pathway enrichment</title>
<p>Gene Set Enrichment Analysis (GSEA) was exploited to study the interpretation and analysis of the long lists of genes generated from high-throughput transcriptomic experiments (<xref ref-type="bibr" rid="ref-18">Mootha <italic>et al</italic>., 2003</xref>; <xref ref-type="bibr" rid="ref-21">Subramanian <italic>et al</italic>., 2005</xref>). Each hub genes of 443 GC samples in TCGA were divided into two groups according to the median expression values. We performed GSEA using the Java GSEA implementation to seek the potential function of targeted genes. We selected annotated gene set c2.cp.kegg.v5.0.symbols.gmt (Version 5.0 of the Molecular Signatures Database) as the reference gene set. The information on the signaling pathways was found by on-line web analysis (<uri xlink:href="https://www.kegg.jp/kegg/pathway.html">https://www.kegg.jp/kegg/pathway.html</uri>).</p>
</sec>
<sec id="s2_2_6">
<title>Statistical methods</title>
<p>For continuous variables, mean &#x00B1; SD was used to express the normal distribution, and the median (range) was used to express the non-normal, whereas count (percentage) was applied to the categorical variables. We chose a <italic>p</italic>-value of &#x003C;0.05 as statistically significant (two-tailed). We used SPSS Version 22.0 and R (version 3.5.3) to carry out these statistical analyses.</p>
</sec>
</sec>
</sec>
<sec id="s3">
<title>Results</title>
<sec id="s3_1">
<title>Data processing</title>
<p>We obtained 139 tissue sample raw files from TCGA (<xref ref-type="table" rid="table-1">Tab. 1</xref>). All selected expression datasets were log2-transformed, then standardized.</p>
<table-wrap id="table-1">
<label>Table 1</label>
<caption>
<title>Clinical characteristics of DGC samples from TCGA</title>
</caption>
<table>
<colgroup>
<col/>
<col/>
<col/>
</colgroup>
<thead>
<tr>
<th>Groups</th>
<th>Number (n &#x003D; 139)</th>
<th>Percentage (%)</th>
</tr>
</thead>
<tbody>
<tr>
<td>Age (years)</td>
<td></td>
<td></td>
</tr>
<tr>
<td>&#x2265;65</td>
<td>78</td>
<td>56.1</td>
</tr>
<tr>
<td>&#x003C;65</td>
<td>61</td>
<td>43.9</td>
</tr>
<tr>
<td>Stage T</td>
<td></td>
<td></td>
</tr>
<tr>
<td>T1</td>
<td>2</td>
<td>1.4</td>
</tr>
<tr>
<td>T2-4</td>
<td>137</td>
<td>98.6</td>
</tr>
<tr>
<td>Stage N</td>
<td></td>
<td></td>
</tr>
<tr>
<td>N0</td>
<td>37</td>
<td>26.6</td>
</tr>
<tr>
<td>N1-3</td>
<td>102</td>
<td>73.4</td>
</tr>
<tr>
<td>Stage M</td>
<td></td>
<td></td>
</tr>
<tr>
<td>M0</td>
<td>128</td>
<td>92.1</td>
</tr>
<tr>
<td>M1</td>
<td>11</td>
<td>7.9</td>
</tr>
<tr>
<td>Grade</td>
<td></td>
<td></td>
</tr>
<tr>
<td>G0-2</td>
<td>44</td>
<td>31.7</td>
</tr>
<tr>
<td>G3</td>
<td>95</td>
<td>68.3</td>
</tr>
</tbody>
</table>
<table-wrap-foot>
<fn id="table-1fn1" fn-type="other">
<p><bold>Note:</bold> Clinical characteristics of the data used in this study. Although we divided the data into nine parts, there are some unknown data in four parts that do not show influence on the following studies.</p>
</fn>
</table-wrap-foot>
</table-wrap>
</sec>
<sec id="s3_2">
<title>Construction of co-expression networks</title>
<p>A network was constructed from the filtered probes which identified 21 modules. The soft-thresholding power 4 was selected to specify the adjacency matrix based on the standard of approximate scale-free topology (<xref ref-type="fig" rid="fig-1">Fig. 1</xref>). We chose the module detection sensitivity deepSplit2, minimum module size 30, and cut height for merging of modules 0.25, which implied that the modules with an eigengene that has a correlation with different clinical characteristics of DGC higher than 0.75 have to be merged (<xref ref-type="fig" rid="fig-2">Fig. 2</xref>).</p>
<fig id="fig-1">
<label>Figure 1</label>
<caption>
<title>Network topology for different soft-thresholding powers.</title>
<p>The numbers in the plots indicate the corresponding soft-thresholding powers. The approximate scale-free topology can be attained at the soft-thresholding power of 4.</p>
</caption>
<graphic mimetype="image" mime-subtype="png" xlink:href="fig-1.png"/>
</fig>
<fig id="fig-2">
<label>Figure 2</label>
<caption>
<title>Gene modules identified by WGCNA.</title>
<p>A gene dendrogram, obtained by clustering dissimilarity based on consensus topological overlap matrix with the corresponding module colors, is indicated by the colored row. Each colored row represents a color-coded module that contains a group of highly connected genes. A total of 21 modules were identified.</p>
</caption>
<graphic mimetype="image" mime-subtype="png" xlink:href="fig-2.png"/>
</fig>
</sec>
<sec id="s3_3">
<title>Correlation between different modules and clinical characteristics of DGC</title>
<p>Similar expression profiles in some modules were found in the analysis. We analyzed the connectivity of eigengenes to understand interactions amongst the 21 co-expressed modules and performed a cluster analysis. In conjunction with <xref ref-type="fig" rid="fig-3">Fig. 3</xref>, significant differences were detected amongst the 21 modules, which may be due to different clinical parameters in the development of GC. For example, royal blue and green-yellow patches may be associated with the stage M of DGC, black and pink patches may be associated with tumor grade, and yellow patches may be negatively correlated with tumor grade.</p>
<fig id="fig-3">
<label>Figure 3</label>
<caption>
<title>Relationships between consensus module eigengenes and different clinical characteristics of DGC.</title>
<p>Each row in the table corresponds to a consensus module, and each column corresponds to a clinical characteristic. The module name is shown on the left side of each cell. Numbers in the table report correlations between the corresponding module eigengenes and characteristics, with the <italic>p</italic>-values printed below the correlations in parentheses. The table is color-coded by correlation according to the color legends. Direction and intensity of correlations are indicated on the right side of the heatmap (green, negatively correlated; red, positively correlated).</p>
</caption>
<graphic mimetype="image" mime-subtype="png" xlink:href="fig-3.png"/>
</fig>
</sec>
<sec id="s3_4">
<title>Identification of hub genes</title>
<p>We found a significant correlation between module membership and clinical characteristics in the royal blue module (<xref ref-type="fig" rid="fig-4">Fig. 4(A)</xref>) and established a co-expression network of the hub genes, as shown in <xref ref-type="fig" rid="fig-4">Fig. 4(B)</xref>. The identification of 25 genes, which included <italic>F5</italic>, Wnt family member 11 (<italic>Wnt11</italic>), and testis associated actin remodeling kinase 1 (<italic>TESK1</italic>) in the royal blue module, may have a significant function in stage M of DGC.</p>
<fig id="fig-4">
<label>Figure 4</label>
<caption>
<title>Identification of hub genes in the royal blue module.</title>
<p>(A) Correlation between the module membership and clinical characteristics in the royal blue module. (B) The density of the circle corresponds to module membership values. The color of the circle represents the core degree of the gene.</p>
</caption>
<graphic mimetype="image" mime-subtype="png" xlink:href="fig-4.png"/>
</fig>
</sec>
<sec id="s3_5">
<title>Survival analysis</title>
<p>Survival analysis was conducted to verify the correlation between the expression of hub genes and the survival time of patients with DGC: high <italic>F5</italic> expression was found to be significantly related to a short OS of DGC (<italic>p</italic> &#x003C; 0.05, [HR 95%CI]: 1.466 (1.056&#x2013;2.034), <xref ref-type="fig" rid="fig-5">Fig. 5(A)</xref>). The Kaplan&#x2013;Meier Plotter on-line database showed that overexpression of <italic>F5</italic> was related to poor prognosis in GC (<italic>p</italic> &#x003C; 0.05, HR &#x003D; 1.66 (1.11&#x2013;2.49), <xref ref-type="fig" rid="fig-5">Fig. 5(B)</xref>).</p>
<fig id="fig-5">
<label>Figure 5</label>
<caption>
<title>Survival analysis and PPI network construction of <italic>F5</italic>.</title>
<p>(A) Kaplan&#x2013;Meier curves of gene groups (<italic>F5</italic>) in the TCGA DGC dataset based on SurvExpress (N &#x003D; 139). The horizontal axis represents time (year) to the event. Outcome event, time scale, concordance index (CI) and <italic>p</italic>-values of the log-rank test are shown. Red and blue curves represent high- and low-risk groups, respectively. (B) The analysis in the Kaplan&#x2013;Meier Plotter on-line database of <italic>F5</italic> in GC. Red and black curves represent high- and low-risk groups, respectively. (C) GEPIA was used for the analysis of <italic>F5</italic> expression in stomach adenocarcinoma (STAD), and the boxplot was plotted. The red and grey boxes represent STAD (N &#x003D; 408) and normal gastric tissues (N &#x003D; 211), respectively. &#x002A;<italic>p</italic> &#x003C; 0.05. (D) PPI networks of <italic>F5</italic> using the STRING tool. Genes are represented as nodes in the plot, and their interactions are denoted by lines.</p>
</caption>
<graphic mimetype="image" mime-subtype="png" xlink:href="fig-5.png"/>
</fig>
</sec>
<sec id="s3_6">
<title>Differential expression of hub genes and PPI network constructions</title>
<p>The encoded product of the <italic>F5</italic> gene is a coagulation factor V, which is a basic cofactor in the coagulation cascade. It has been reported (<xref ref-type="bibr" rid="ref-26">Vossen <italic>et al</italic>., 2011</xref>) that polymorphisms in <italic>F5</italic>, such as <italic>F5</italic> Leiden, were related to increased risk of colorectal cancer. On-line data analysis revealed a significant overexpression level of <italic>F5</italic> in GC tissues compared to gastric tissues (<xref ref-type="fig" rid="fig-5">Fig. 5(C)</xref>). The PPI network indicated that the protein encoded by <italic>F5</italic> interacted with bone morphogenetic protein 4 (BMP4) and amphiregulin (AREG) and interacted indirectly with Wnt11 (<xref ref-type="fig" rid="fig-5">Fig. 5(D)</xref>).</p>
</sec>
<sec id="s3_7">
<title>Cytological experiments to verify the effect of selected hub genes on GC cells</title>
<p>We verified <italic>F5</italic> mRNA expression levels in four GC cell lines including MGC803, BGC823, HGC27, and SGC7901. <xref ref-type="fig" rid="fig-6">Fig. 6(A)</xref> shows that <italic>F5</italic> was expressed to varying degrees in the four GC cell lines. The SGC7901 cell line was used to further test the function of <italic>F5</italic>. <xref ref-type="fig" rid="fig-6">Fig. 6(B)</xref> illustrates the efficiency of <italic>F5</italic> knockdown in the SGC7901 cell line. MTT assays confirmed that inhibition of <italic>F5</italic> slightly suppressed the proliferation of GC cells to 25% (<italic>p</italic> &#x003C; 0.01, <xref ref-type="fig" rid="fig-6">Fig. 6(C)</xref>). At 24-h, a Transwell migration assay indicated that when the <italic>F5</italic> gene was silenced, the migration of GC cells was significantly inhibited from 383 to 19 (cell number/field, <italic>p</italic> &#x003C; 0.001, <xref ref-type="fig" rid="fig-6">Figs. 6(D)</xref>&#x2013;<xref ref-type="fig" rid="fig-6">6(E)</xref>).</p>
<fig id="fig-6">
<label>Figure 6</label>
<caption>
<title><italic>In vitro</italic> experiments.</title>
<p>(A) Expression of <italic>F5</italic> in the MGC803, BGC823, HGC27, and SGC7901 cell lines. (B) Expression of <italic>F5</italic> in SGC7901 cell line after <italic>F5</italic> gene knockdown. (C) The outcome of MTT assay. (D&#x2013;E) The outcome of the Transwell migration assay. &#x002A;&#x002A;<italic>p</italic> &#x003C; 0.01; &#x002A;&#x002A;&#x002A;<italic>p</italic> &#x003C; 0.001.</p>
</caption>
<graphic mimetype="image" mime-subtype="png" xlink:href="fig-6.png"/>
</fig>
</sec>
<sec id="s3_8">
<title>GSEA pathway enrichment</title>
<p>In this study, GSEA was used to explore the possible molecular mechanism of <italic>F5</italic> in the prognosis of GC using 443 samples from the TCGA database. We identified two pathways that were clearly associated with the development of GC which were &#x201C;basal cell carcinoma&#x201D; (NES &#x003D; 1.72, NOM <italic>p</italic> &#x003D; 0.002) (<xref ref-type="fig" rid="fig-7">Fig. 7(A)</xref>) and &#x201C;TGF-&#x03B2; signaling pathway&#x201D; (NES &#x003D; 1.51, NOM <italic>p</italic> &#x003D; 0.044) (<xref ref-type="fig" rid="fig-7">Fig. 7(B)</xref>). Information pertaining to the basal cell carcinoma signaling pathway was shown in <xref ref-type="fig" rid="fig-8">Fig. 8</xref> and <xref ref-type="table" rid="table-2">Tab. 2</xref>. The impact of <italic>F5</italic> on the survival and prognosis of DGC may be mediated through a link with the above pathways.</p>
<fig id="fig-7">
<label>Figure 7</label>
<caption>
<title>GSEA analysis of <italic>F5</italic> in gastric cancer patients using the TCGA database.</title>
<p>(A&#x2013;B) Two pathways ranked top in the <italic>F5</italic>-related predictive outputs.</p>
</caption>
<graphic mimetype="image" mime-subtype="png" xlink:href="fig-7.png"/>
</fig>
<fig id="fig-8">
<label>Figure 8</label>
<caption>
<title>Information pertaining to the basal cell carcinoma pathway from the KEGG on-line database.</title>
</caption>
<graphic mimetype="image" mime-subtype="png" xlink:href="fig-8.png"/>
</fig>
<table-wrap id="table-2">
<label>Table 2</label>
<caption>
<title>Information of basal cell carcinoma signaling pathway</title>
</caption>
<table>
<colgroup>
<col/>
<col/>
<col/>
<col/>
<col/>
<col/>
<col/>
</colgroup>
<thead>
<tr>
<th>Name</th>
<th>Probe</th>
<th>Gene title</th>
<th>Rank in gene list</th>
<th>Rank metric score</th>
<th>Running es</th>
<th>Core enrichment</th>
</tr>
</thead>
<tbody>
<tr>
<td>Row_0</td>
<td>WNT7B</td>
<td>wingless-type MMTV integration site family, member 7B</td>
<td>58</td>
<td>0.25326744</td>
<td>0.055809945</td>
<td>Yes</td>
</tr>
<tr>
<td>Row_1</td>
<td>FZD9</td>
<td>frizzled homolog 9 (<italic>Drosophila</italic>)</td>
<td>226</td>
<td>0.20891821</td>
<td>0.09464167</td>
<td>Yes</td>
</tr>
<tr>
<td>Row_2</td>
<td>FZD6</td>
<td>frizzled homolog 6 (<italic>Drosophila</italic>)</td>
<td>257</td>
<td>0.20379044</td>
<td>0.14055689</td>
<td>Yes</td>
</tr>
<tr>
<td>Row_3</td>
<td>FZD2</td>
<td>frizzled homolog 2 (<italic>Drosophila</italic>)</td>
<td>331</td>
<td>0.19461304</td>
<td>0.18172245</td>
<td>Yes</td>
</tr>
<tr>
<td>Row_4</td>
<td>AXIN1</td>
<td>axin 1</td>
<td>343</td>
<td>0.19329599</td>
<td>0.22632872</td>
<td>Yes</td>
</tr>
<tr>
<td>Row_5</td>
<td>WNT5A</td>
<td>wingless-type MMTV integration site family, member 5A</td>
<td>522</td>
<td>0.17658667</td>
<td>0.25692296</td>
<td>Yes</td>
</tr>
<tr>
<td>Row_6</td>
<td>FZD1</td>
<td>frizzled homolog 1 (<italic>Drosophila</italic>)</td>
<td>871</td>
<td>0.15791881</td>
<td>0.2728651</td>
<td>Yes</td>
</tr>
<tr>
<td>Row_7</td>
<td>DVL1</td>
<td>dishevelled, dsh homolog 1 (<italic>Drosophila</italic>)</td>
<td>1000</td>
<td>0.15183835</td>
<td>0.3006866</td>
<td>Yes</td>
</tr>
<tr>
<td>Row_8</td>
<td>SHH</td>
<td>sonic hedgehog homolog (<italic>Drosophila</italic>)</td>
<td>1274</td>
<td>0.14071888</td>
<td>0.31713563</td>
<td>Yes</td>
</tr>
<tr>
<td>Row_9</td>
<td>LEF1</td>
<td>lymphoid enhancer-binding factor 1</td>
<td>1647</td>
<td>0.12838289</td>
<td>0.3247089</td>
<td>Yes</td>
</tr>
<tr>
<td>Row_10</td>
<td>WNT8B</td>
<td>wingless-type MMTV integration site family, member 8B</td>
<td>1982</td>
<td>0.11861961</td>
<td>0.33229342</td>
<td>Yes</td>
</tr>
<tr>
<td>Row_11</td>
<td>BMP2</td>
<td>bone morphogenetic protein 2</td>
<td>2263</td>
<td>0.11144068</td>
<td>0.341462</td>
<td>Yes</td>
</tr>
<tr>
<td>Row_12</td>
<td>DVL2</td>
<td>dishevelled, dsh homolog 2 (<italic>Drosophila</italic>)</td>
<td>2314</td>
<td>0.11014112</td>
<td>0.3642344</td>
<td>Yes</td>
</tr>
<tr>
<td>Row_13</td>
<td>WNT4</td>
<td>wingless-type MMTV integration site family, member 4</td>
<td>2655</td>
<td>0.10189386</td>
<td>0.36753878</td>
<td>Yes</td>
</tr>
<tr>
<td>Row_14</td>
<td>BMP4</td>
<td>bone morphogenetic protein 4</td>
<td>2661</td>
<td>0.10179675</td>
<td>0.39107803</td>
<td>Yes</td>
</tr>
<tr>
<td>Row_15</td>
<td>CTNNB1</td>
<td>catenin (cadherin-associated protein), beta 1, 88kDa</td>
<td>2816</td>
<td>0.09821845</td>
<td>0.4047691</td>
<td>Yes</td>
</tr>
<tr>
<td>Row_16</td>
<td>SMO</td>
<td>smoothened homolog (<italic>Drosophila</italic>)</td>
<td>2911</td>
<td>0.09612198</td>
<td>0.4215974</td>
<td>Yes</td>
</tr>
<tr>
<td>Row_17</td>
<td>GLI1</td>
<td>glioma-associated oncogene homolog 1 (zinc finger protein)</td>
<td>2970</td>
<td>0.09484449</td>
<td>0.44030344</td>
<td>Yes</td>
</tr>
<tr>
<td>Row_18</td>
<td>WNT2</td>
<td>wingless-type MMTV integration site family member 2</td>
<td>3116</td>
<td>0.09167766</td>
<td>0.45300686</td>
<td>Yes</td>
</tr>
<tr>
<td>Row_19</td>
<td>WNT6</td>
<td>wingless-type MMTV integration site family, member 6</td>
<td>3510</td>
<td>0.08424388</td>
<td>0.44897255</td>
<td>Yes</td>
</tr>
<tr>
<td>Row_20</td>
<td>WNT11</td>
<td>wingless-type MMTV integration site family, member 11</td>
<td>3599</td>
<td>0.08273254</td>
<td>0.46302778</td>
<td>Yes</td>
</tr>
<tr>
<td>Row_21</td>
<td>FZD10</td>
<td>frizzled homolog 10 (<italic>Drosophila</italic>)</td>
<td>3616</td>
<td>0.08251304</td>
<td>0.48138544</td>
<td>Yes</td>
</tr>
<tr>
<td>Row_22</td>
<td>GLI2</td>
<td>GLI-Kruppel family member GLI2</td>
<td>4139</td>
<td>0.0728891</td>
<td>0.46689105</td>
<td>Yes</td>
</tr>
<tr>
<td>Row_23</td>
<td>SUFU</td>
<td>suppressor of fused homolog (<italic>Drosophila</italic>)</td>
<td>4625</td>
<td>0.06510936</td>
<td>0.45281202</td>
<td>Yes</td>
</tr>
<tr>
<td>Row_24</td>
<td>WNT10A</td>
<td>wingless-type MMTV integration site family, member 10A</td>
<td>4766</td>
<td>0.06254979</td>
<td>0.4589958</td>
<td>Yes</td>
</tr>
<tr>
<td>Row_25</td>
<td>AXIN2</td>
<td>axin 2 (conductin, axil)</td>
<td>4800</td>
<td>0.06199568</td>
<td>0.47152016</td>
<td>Yes</td>
</tr>
<tr>
<td>Row_26</td>
<td>WNT8A</td>
<td>wingless-type MMTV integration site family, member 8A</td>
<td>5028</td>
<td>0.058139</td>
<td>0.47140998</td>
<td>Yes</td>
</tr>
<tr>
<td>Row_27</td>
<td>WNT9B</td>
<td>wingless-type MMTV integration site family, member 9B</td>
<td>5039</td>
<td>0.05796774</td>
<td>0.48438177</td>
<td>Yes</td>
</tr>
</tbody>
</table>
</table-wrap>
</sec>
</sec>
<sec id="s4">
<title>Discussion</title>
<p>The molecular mechanism involved in the development of DGC remains unclear. In this study, we attempted to identify a possible molecular mechanism through WGCNA and found that <italic>F5</italic> may be related to stage M of DGC. GSEA indicated that <italic>F5</italic> may not only have an effect on the development of DGC but may also be important in all GCs. The cytological experiments in this study confirmed that <italic>F5</italic> can significantly affect cell migration of GC.</p>
<p>The encoded product of the <italic>F5</italic> is the coagulation factor V, which is known as &#x2018;clotting factor&#x2019;. The protein circulates in plasma and participates in thrombin activation with factor Xa. Most existing reports focus on the coagulation function of <italic>F5</italic>, including the role of <italic>F5</italic> and its protein in thrombosis (<xref ref-type="bibr" rid="ref-31">Zhang <italic>et al</italic>., 2018a</xref>; <xref ref-type="bibr" rid="ref-32">Zhang <italic>et al</italic>., 2018b</xref>), and DIC (<xref ref-type="bibr" rid="ref-12">Kou <italic>et al</italic>., 2019</xref>) in patients with hematological malignancies.</p>
<p><italic>F5</italic> has been reported in various tumor types as a marker. In breast cancer, the expression of <italic>F5</italic> may inform clinical treatment decisions and prognosis of invasive breast cancer, indicating <italic>F5</italic> as a potential biomarker of invasive breast cancer (<xref ref-type="bibr" rid="ref-25">Tinholt <italic>et al</italic>., 2018</xref>). However, another study (<xref ref-type="bibr" rid="ref-9">Ivancic <italic>et al</italic>., 2014</xref>) revealed that the increased risk of developing colorectal cancer is associated with <italic>F5</italic> in ApcPirc/&#x002B; rats. Analysis using on-line databases showed significant over-expression level of <italic>F5</italic> in GC tissues, and that high <italic>F5</italic> expression can predict poor prognosis in both DGC and GC.</p>
<p>This study showed that the two pathways obtained from GSEA were closely related to <italic>F5</italic>. The basal cell carcinoma pathway includes the Wnt and TGF-&#x03B2; pathways. As these pathways were screened based on data of GC, the function of <italic>F5</italic> in GC may be similar to basal cell carcinoma. According to GSEA analysis, we found that the core molecules which may have interaction with <italic>F5</italic> in the basal cell carcinoma signaling pathway belong to the Wnt signaling pathway. In previous PPI analysis, we found that <italic>F5</italic> is indirectly related to Wnt11. Furthermore, a study (<xref ref-type="bibr" rid="ref-11">Katoh and Katoh, 2009</xref>) also indicated that the canonical Wnt-to-Wnt11 signaling pathway is involved in cellular migration in tumor invasion during carcinogenesis. Therefore, <italic>F5</italic> may participate in interactions with the Wnt signaling pathway.</p>
<p>Numerous studies have reported that the TGF-&#x03B2; and Wnt signaling pathways exert effects on the development of GC. Epithelial to mesenchymal transition (EMT) is a central biological process in which tumor cells lose epithelial characteristics and acquire mesenchymal features that make cancer cells more migratory and invasive (<xref ref-type="bibr" rid="ref-24">Thiery <italic>et al</italic>., 2009</xref>). Gastric epithelial cells acquire mesenchymal markers, become more invasive, and show stemness and metastasis during EMT (<xref ref-type="bibr" rid="ref-23">Thiery, 2002</xref>; <xref ref-type="bibr" rid="ref-28">Ye and Weinberg, 2015</xref>). The process of EMT is associated with certain signaling pathways, including the Wnt and TGF-&#x03B2; pathways. A study (<xref ref-type="bibr" rid="ref-8">Huang <italic>et al</italic>., 2015</xref>) revealed that Wnt signaling can promote progression in GC cells by EMT. Activation of the TGF-&#x03B2;/Smad signaling pathway can also induce EMT and then promote the metastasis in GC (<xref ref-type="bibr" rid="ref-33">Zhang <italic>et al</italic>., 2018c</xref>).</p>
<p>Previous studies (<xref ref-type="bibr" rid="ref-17">Luo <italic>et al</italic>., 2019</xref>) have suggested that GC patients have higher TGF-&#x03B2; levels in serum compared to healthy individuals. Elevated TGF-&#x03B2; levels are closely related to poor prognosis and shorter OS in GC patients (<xref ref-type="bibr" rid="ref-7">Hu <italic>et al</italic>., 2014</xref>). Furthermore, it has been confirmed (<xref ref-type="bibr" rid="ref-3">Chiurillo, 2015</xref>) that specific mechanisms up-regulate components of the Wnt signaling pathway. Also, the inactivation of inhibitors of Wnt signaling plays an important role in GC. Other studies (<xref ref-type="bibr" rid="ref-1">Boussioutas <italic>et al</italic>., 2003</xref>; <xref ref-type="bibr" rid="ref-13">Kurayoshi <italic>et al</italic>., 2006</xref>) have found that Wnt-5a (a molecule on the Wnt signaling pathway) was up-regulated in all types of GC and acted to promote invasion, migration and poor prognosis of patients with GC. Furthermore, suppression of the Wnt signaling pathway can inhibit the growth and migration of GC (<xref ref-type="bibr" rid="ref-5">Gao <italic>et al</italic>., 2018</xref>; <xref ref-type="bibr" rid="ref-16">Liu <italic>et al</italic>., 2018</xref>). The above studies are consistent with our cytological experiments and bioinformatics analysis. Based on this evidence, we hypothesize that the effect of <italic>F5</italic> on the survival and prognosis of DGC might be through a link with the Wnt and/or the TGF-&#x03B2; signaling pathways.</p>
<p>In this study, the <italic>F5</italic> gene was screened from samples of DGC. We found that <italic>F5</italic> not only has an effect on DGC but also on GC based on PPI networks, cytological experiments, and GSEA studies. Cytological experiments confirmed that <italic>F5</italic> significantly affected the migration of GC cells, which is consistent with our discovery by WGCNA. <italic>F5</italic> is associated with stage M of DGC. There are many unsolved problems concerning the mechanism of <italic>F5</italic> in GC, which warrant further investigation through cytological and zoological experiments.</p>
</sec>
<sec id="s5">
<title>Conclusions</title>
<p>This study suggested that high <italic>F5</italic> expression was related to poor prognosis in patients with DGC and GC by promoting cell migration and this might participate in the regulation of the Wnt and/or the TGF-&#x03B2; signaling pathways. This provides a basis for further analysis of the prognosis and treatment of DGC and GC.</p>
</sec>
</body>
<back><fn-group>
<fn fn-type="conflict">
<p><bold>Acknowledgement:</bold> We would like to acknowledge the provider of the space and equipment for conducting the experiments. They were the Ministry of Education (China Medical University, Shenyang, China), Key Laboratory of Precision Diagnosis and Treatment of Gastrointestinal Tumors.</p>
</fn>
<fn fn-type="other">
<p><bold>Availability of Data and Materials:</bold> The datasets analyzed during the current study are available from the corresponding author on reasonable request.</p>
</fn>
<fn fn-type="other">
<p><bold>Author Contribution:</bold> The authors confirm contribution to the paper as follows: Study conception and design: Mengyi Tang, Bowen Yang, Yunpeng Liu, Zhi Li, Xiujuan Qu; data collection: Mengyi Tang, Bowen Yang, Chuang Zhang, Chaoxu Zhang, Dan Zang; analysis and interpretation of results: Mengyi Tang, Bowen Yang, Zhi Li, Xiujuan Qu; draft manuscript preparation: Mengyi Tang, Bowen Yang, Libao Gong. All authors reviewed the results and approved the final version of the manuscript.</p>
</fn>
<fn fn-type="other">
<p><bold>Funding Statement:</bold> We would also like to thank these funds, including the National Natural Science Foundation of China (Nos. 81972331, 81972751, 81572374), The National Key Research and Development Program of China (2017YFC1308900), Technological Special Project of Liaoning Province of China (2019020176-JH1/103), Science and Technology Plan Project of Liaoning Province (NO. 2013225585) and The General Projects of Liaoning Province Colleges and Universities (LFWK201706).</p>
</fn>
<fn fn-type="conflict">
<p><bold>Conflicts of Interest:</bold> In respect of the authorship, research, and/or publication of this article, all the authors declared no potential conflicts of interest.</p>
</fn>
</fn-group>
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