Abstract
Background/Aim: The present study investigated the oncogenic functions of TACC3 in the progression of gastric cancer (GC). Materials and Methods: We analysed TACC3 in relation to cell growth, invasion capability, expression of epithelial-mesenchymal transition (EMT)-related markers, and ERK/Akt/cyclin D1 signaling factors. The correlation between the immunohistochemically confirmed expression of TACC3 and clinical factors was also analyzed. Results: The increased proliferation and invasion of TACC3-over-expressing GC cells was accompanied by altered regulation of EMT-associated markers and activation of ERK/Akt/cyclin D1 signaling. Immunohistochemical analysis of TACC3 in human GC tissues revealed that its expression is correlated with aggressive characteristics and poor prognosis of intestinal-type GC. Conclusion: TACC3 contributes to gastric tumorigenesis by promoting EMT via the ERK/Akt/cyclin D1 signaling pathway. The correlation between TACC3 expression and multiple clinicopathological variables implies that its effective therapeutic targeting in GC will depend on the tumor subtype.
Gastric cancer (GC) is the third leading cause of cancer-associated mortality worldwide, but the development of effective treatment is complicated by its high level of genetic and cellular heterogeneity, including a heterogeneous tumor microenvironment (1, 2). Despite recent advances in diagnostic, surgical, and pharmacological interventions, GC tends to progress and thus, often has a dismal prognosis with a high rate of mortality (3). Surgical resection in advanced GC is typically followed by radio-chemotherapy, which can prolong overall survival. However, the 5-year survival in advanced GC patients treated with modern chemotherapy protocols is 3.1% (4). Furthermore, the poor prognosis of patients with therapeutically resistant GC remains a major challenge in clinical oncology. Novel strategies for the identification of effective prognostic biomarkers of therapeutic resistance are needed to overcome the poor prognosis associated with GC.
Targeted cancer therapy is a novel, emerging research field that is anticipated to improve prognosis of many types of cancer. Among the several targets, the epithelial-mesenchymal transition (EMT) has been investigated as one of the critical regulators of chemo-resistance of GC (5), tumor progression, and metastatic spread of diverse cancers (6, 7). The EMT involves the dynamic switching or transdifferentiation from round-shaped, polarized epithelial cells into spindle-shaped, motile mesenchymal cells, whose invasiveness and migratory capacity contribute to cancer progression and distant metastasis (8-10). The distinctive feature of the EMT is the repression of the epithelial cell marker E-cadherin (11), accompanied by the expression of several transcription molecules and the mesenchymal cell markers snail, slug, twist and ZEB (8, 12). Regarding signaling molecules, triggers of EMT include extracellular signal-regulated kinase (ERK), phosphatidylinositol 3-kinase (PI3K)/Akt, cyclin D1, and β-catenin, all of which have also been involved in cancer progression and metastasis (13-15).
The transforming acidic coiled-coil (TACC) family consists of centrosomal- and microtubule-associated proteins that participate in the regulation of cell division (16). TACC3 is located in 4p16.3; aberrant location can increase likelihood of development of several cancers and neurodegenerative diseases (17). TACC3 is a highly conserved, microtubule-related protein with a C-terminal coiled-coil domain, critically involved in cancer development (18). By contributing to genomic instability and tumorigenesis through the regulation of transcriptional activities, aberrant TACC3 expression can interfere with mitosis (19) and has been demonstrated to be associated with a poor clinical outcome in several human cancers (20-23). Knockdown of TACC3 suppressed the growth, spread, and tumorigenic properties of renal cell carcinoma cells (24). Genetic analysis of patient samples has indicated that TACC3 over-expression is related with chemoresistance in ovarian cancer and aggressiveness in breast carcinoma (25, 26). Elevated expression of TACC3 is also a poor prognostic indicator in non-small cell lung cancer (21). In cervical carcinoma, TACC3 has been shown to trigger the ERK and PI3K/Akt signaling pathways to promote the EGF-mediated EMT (27, 28).
The mechanism underlying TACC3-mediated tumor progression and metastasis in GC is unclear, but this knowledge would have important clinical implications. Thus, the purpose of this investigation was to elucidate the molecular mechanisms of TACC3 expression in correlation with carcinogenesis in GC.
Materials and Methods
Cell culture. AGS, MKN45, SNU-719 and SNU-638 cells were obtained from the American Type Culture Collection (Manassas, VA, USA) and Korean Cell Line Bank (Seoul, Republic of Korea). AGS, MKN45, SNU-719 and SNU-638 cells were maintained in RPMI-1640 medium (HyClone, Logan, UT, USA) containing 10% fetal bovine serum (FBS) and 1% penicillin/streptomycin and cultured in a humidified incubator at 37°C with 5% CO2.
Antibodies, reagents, and plasmid constructs. Antibodies against TACC3 and actin were purchased from Santa Cruz Biotechnology (Dallas, TX, USA); anti-flag antibody was from Sigma-Aldrich (St. Louis, MO, USA); antibodies against E-cadherin, slug, snail, β-catenin, vimentin, ERK1/2, p-ERK1/2 (T202/Y204), Akt, anti-p-Akt (S473), cyclin D1, and actin were acquired from Cell Signaling Technology (Danvers, MA, USA). Invasion assay was performed using cell invasion assay kits (Chemicon, #ECM550, Sigma-Aldrich). 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) was bought from Sigma-Aldrich.
Western blot analysis. Transfected cells were washed with PBS and lysed in nuclear extraction buffer [20 mM 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) (pH 7.6), 20% glycerol, 250 mM NaCl, 1.5 mM MgCl2, 0.1% Triton X-100, 1 mM phenylmethylsulfonyl fluoride, 1 mM 1,4-dithiothreitol, and protease inhibitor cocktail (Roche, Basel, Switzerland)]. Proteins (30 μg) were separated by 8-12% polyacrylamide gel electrophoresis containing SDS and incubated with primary antibodies for 16 h at 4°C. Bands were quantified using an electrochemiluminescence system (Millipore, Burlington, MA, USA) and an LAS-4000 image analyzer (Fujifilm, Tokyo, Japan). Actin served as a loading control.
Cell proliferation assay. Exponentially growing GC cells were harvested and then spread in 96-well microplates (200 μl medium, 2×104 cells/ml). After the designated time elapsed, the cell suspension was dissolved with DMSO after being incubated with 2 mg MTT/ml for 3 h. The optical density was spectrophotometrically measured at 490 nm.
Cell invasion assay. The invasion assay was carried out with an invasion assay kit (Chemicon, Temecula, CA, USA), according to the manufacturer’s instructions. A cell suspension in FBS-free medium was added to the cell-culture inserts and then placed into the lower chamber containing complete medium. After passing through the extracellular matrix layer during 24 h of incubation, cells attached to the polycarbonate membrane were stained and counted.
Transfection. AGS and SNU-638 cells were transiently transfected with 5 μg Flag-TACC3 (over-expression construct) or with a small hairpin RNA (shRNA) targeting human TACC3 by electroporation using the Neon transfection system (Invitrogen, CA, USA), with one 30-msec pulse at 1300 V following the manufacturer’s recommendation. The cells were maintained in complete medium with 10% FBS for 24-48 h and harvested for western blotting, invasion, and MTT assays.
Human tissue samples and clinical data. The patient cohort included in this study had stage II/III GC and had participated in a phase III open-label multi-center randomized controlled trial (the CLASSIC trial) conducted between 2006 and 2009, in which D2 gastrectomy alone was compared with adjuvant chemotherapy after D2 gastrectomy (29, 30). The median follow-up period of the cohort was 67 months (range=1-92 months). Survival was calculated as disease-free survival (DFS) and overall survival (OS). Data regarding age, sex, stage, microsatellite instability status, Epstein-Barr virus (EBV) infection, HER2 amplification, and histological features were collected from the records of the CLASSIC trial. Gastric cancer stage was assessed following the sixth version of the American Joint Committee on Cancer (AJCC) criteria. This study was approved by the Institutional Review Board of Chonnam National University Hwasun Hospital (CNUHH-2020-149).
Immunohistochemistry (IHC). Tissue microarrays consisting of two 3-mm diameter cores representing each tumor were prepared from FFPE blocks and used for immunohistochemistry (30). Tissue sections (4 μm) were subjected to IHC using the Bond-max autostainer (Leica Microsystems, Buffalo Grove, IL, USA). The sections were pretreated with ER1 solution (for epitope retrieval using citrate buffer at pH 6.0) for 15 min and then incubated with anti-TACC3 antibody (Santa Cruz, catalogue no. sc-376883) at a 1:100 dilution. Negative controls were prepared as described above but omitting the primary antibodies. Cytoplasmic immunoreactivity was assessed using a four-tier grade: 0, null staining; 1+, weak reactivity; 2+, moderate reactivity; and 3+, strong reactivity. The labeled area as a proportion of the entire tumor area was determined as a percentage. The IHC scores for TACC3 immunopositivity were quantified by multiplication of the staining grade with the labeled area percentage as previously described (31). TACC3-positive immune cells were counted in five different densely labeled foci at 400× magnification and the counts were then averaged. IHC slides were assessed by two experienced pathologists (JHL and KHL) blinded to the clinical details; in the event of disagreement between the observers, immunohistochemical staining was re-evaluated. The two pathologists re-assessed the cases jointly and came to an agreement for inconclusive samples.
Statistical analysis. Statistical analyses were carried out using Graph Pad Prism version 6 (Graph Pad, La Jolla, CA, USA) and SPSS version 23.0 software for Windows (SPSS, Chicago, IL, USA). Student’s t-test or the Mann-Whitney test was used to compare differences between two groups. Chi-squared and Fisher’s exact tests were used to evaluate differences between clinicopathological variables and TACC3 expression. The effect of single variables on DFS or OS was determined using univariate (Kaplan–Meier method with log-rank tests) and multivariate (Cox’s proportional hazards model) analyses. Survival was calculated in R (version 4.0.2), with an optimal cut-off point analysis using the surv_cutpoint function from the R-package Survminer (version 0.4.8). A p-value of <0.05 was considered to indicate statistical significance, and a p-value between 0.05 and 0.01 marginal significance.
Results
Aberrant expression of TACC3 protein in intestinal-type gastric cancer. TACC3 expression in human GC tissues was further investigated in an IHC study using tissue microarrays using 629 gastric tumors classified according to histological type using the Lauren classification (32). TACC3 staining was observed in normal gastric epithelial cells (Figure 1A, left panel) and the four categories of the intensity of TACC3 immunostaining are shown in Figure 1A (right panel). Among the 303 intestinal-type GCs, high-level TACC3 expression was detected in 195 (64.4%), and low-level expression in the remaining 108 (35.6%). TACC3 expression correlated significantly with the tumor grade (low histologic grade vs. high histologic grade; p=0.024). Of the 326 diffuse-type GCs, high-level TACC3 expression was determined in 98 (30.1%) and low-level expression in the remaining 228 (69.9%). TACC3 was variably expressed in human gastric cancer tissues (Figure 1A) with the highest frequency in the intestinal-type (Figure 1B) among diffuse-type gastric cancers. We investigated TACC3 gene expression profiles in cancers by searching available data from the Oncomine microarray database. We found that TACC3 was significantly over-expressed in a set of 26 gastric intestinal-type adenocarcinomas, compared to that in 31 gastric mucosa (p-value=7.52×10–10; fold change=5.531) (Figure 1C, left panel). In addition, TACC3 was significantly over-expressed in a set of 65 gastric intestinal-type adenocarcinomas, compared to that in 26 gastric mucosa (p-value=3.05×10–9; fold change=1.670) (Figure 1C, right panel). TACC3 expression was observed in the intestinal-type gastric cell lines with a relative value of expression exceeding 1.5 compared with diffuse-type gastric cell lines (MKN45) (Figure 1D). These data corroborated our findings, indicating that TACC3 levels were significantly over-expressed in gastric intestinal-type adenocarcinomas (Figure 1B and C).
TACC3 was over-expressed in gastric cancer. (A and B) Representative IHC images for TACC3 in normal human gastric tissues (left) and gastric cancers (right) (original magnification, ×400) (A). TACC3 expression rate was analyzed according to the histological subtype of human gastric cancer including Intestinal-type and diffuse-type histology (B). (C and D) Gene expression data in Oncomine was analyzed. The thick bars in the boxes are average expression levels and the boxes represent 95% of the samples. The error bars are above or below the boxes and the range of expression levels is enclosed by two dots. (D) Four different gastric cancer cells were analyzed for TACC3 expression using immunoblotting (left). TACC3 expression level was quantified through scanning densitometry with actin as an internal control (right).
Correlation between IHC expression of TACC3 and clinicopathologic variables of the gastric cancer cohort. TACC3 expression in human GC tissues was further investigated in an IHC study using tissue microarrays prepared from 629 gastric tumors classified according to histological type using the Lauren classification (32). TACC3 expression was mainly observed in the cytoplasm of both tumor cells and immune cells (Figure 1A). Among the 303 intestinal-type GCs, high-level TACC3 expression was detected in 195 (64%), and low-level expression in the remaining 108 (36%) (Table I). In addition, the expression of TACC3 correlated significantly with the histologic grade of the tumor (low grade vs. high grade; p=0.024), the depth of invasion (T1-T2 vs. T3-4; p=0.026), and perineural invasion by the tumor cells (p=0.009), with a marginal association with lymph node (LN) metastasis (N0 or N1 vs. N2 or higher; p=0.052) and tumor location (upper body vs. lower body; p=0.099) (Table I). The correlation between TACC3-positive immune cells in intestinal-type GC and EBV infection was also statistically significant (p=0.001). Of the 326 diffuse-type GCs, high-level TACC3 expression was determined in 98 (30%) and low-level expression in the remaining 228 (70%) (Table I). TACC3 expression in diffuse-type GC correlated significantly with lymphovascular invasion (p<0.001), microsatellite instability (p=0.004), and EBV infection (p<0.001) (Table II). The correlation between the number of TACC3-positive immune cells in diffuse-type GC and EBV infection was also significant (p<0.001) (Table II).
Correlation between TACC3 expression in intestinal-type gastric cancer (n=303) and clinicopathological variables.
Correlation between TACC3 expression in diffuse-type gastric cancer (n=326) and clinicopathological variables.
TACC3 over-expression increases the proliferation and migration of intestinal-type GC cells. To explore the functional role of TACC3 in intestinal-type GC, genetically modulated cell lines over-expressing TACC3 were established. SNU-638 GC cell lines were transfected with a TACC3-over-expression vector (Flag-TACC3) or the empty vector (Flag). The efficacy of TACC3 over-expression was examined by western blot analysis (Figure 2A). In SNU-638 cells over-expressing TACC3, proliferation was significantly upregulated (Figure 2B). TACC3 over-expression also expanded the invasive capacities of the cells, as revealed in a transwell cell invasion assay (Figure 2C and D).
TACC3 over-expression enhances the growth and invasiveness of gastric cancer cells. (A) SNU-638 cells were transfected with Flag or Flag-tagged TACC3 plasmids. Forty-eight hours after transfection the cells were harvested and lysates were prepared and analyzed by immunoblotting using the indicated antibodies. (B) MTT assay was performed to estimate proliferation of SNU-638 cells over-expressing TACC3. (C and D) SNU-638 cells over-expressing Flag-TACC3 were pretreated with 10 μg/ml mitomycin C for 1 h at 37°C, washed twice with PBS and then were subjected to invasion assays. The results are expressed as the mean±standard deviation (SD) of at least three independent experiments (*p<0.05).
TACC3-knockdown decreases proliferation and migration by intestinal-type GC cells. Previous studies have demonstrated a role of TACC3 in proliferation and invasion of cervical cancer and osteosarcoma cells (27, 28). To explore the functional role of TACC3 in GC, genetically modulated TACC3-knockdown cells were established. AGS cell lines were transfected with a TACC3-knockdown vector (shTACC3) or the empty vector (shLuc). TACC3 expression was silenced with shRNA, and interference efficacy was validated by western blot analysis (Figure 3A). In AGS cells with TACC3-knockdown, proliferation was significantly down-regulated compare to control cells (shLuc) (Figure 3B). Moreover, TACC3-knockdown significantly reduced transwell invasion (Figure 3C and D). Together, these results indicated that depletion of TACC3 dramatically reduced the proliferation and invasion of gastric cancer cells.
TACC3-knockdown decreases the growth and invasiveness of gastric cancer cells. AGS cells were transfected with shLuc (control) or TACC3-targeted shRNA (shTACC3), and subjected to immunoblotting for TACC3 and actin. (B) MTT assay was performed to estimate proliferation of AGS cells with TACC3-knockdown. (C and D) AGS cells with TACC3-knockdown (shTACC3) were pretreated with 10 μg/ml mitomycin C for 1 h at 37°C, washed twice with PBS and then were subjected to invasion assays. The results are expressed as the mean±standard deviation (SD) of at least three independent experiments (*p<0.05).
The epithelial-mesenchymal transition is regulated by TACC3 expression via the ERK/Akt/cyclin D1 signaling pathway. We have observed that TACC3 promotes epithelial-mesenchymal transition (EMT) through the activation of PI3K/Akt and ERK signaling pathways in HeLa cells (28). The results described above identified a role of TACC3 in increasing the motility of GC cells, thus implicating this protein in the progression of GC. Because cancer cell motility is closely linked to the EMT, we investigated the role of TACC3 in this process. Thus, the expression of EMT-related markers (E-cadherin, β-catenin, snail, slug, and vimentin) in SNU-638 cells over-expressing TACC3 was examined by western blot analysis. Over-expression of TACC3 induced upregulation of the mesenchymal markers β-catenin, snail, slug, and vimentin and downregulation of E-cadherin (Figure 4A). Moreover, western blot analysis showed an increase in the phosphorylation of Akt and ERK and up-regulation of cyclin D1 in cells over-expressing TACC3 (Figure 4B). By contrast, knockdown of TACC3 in AGS cells reduced expression of β-catenin, snail, slug, and vimentin, but enhanced E-cadherin expression (Figure 4C). In addition, in TACC3-knockdown AGS cells, however, the phosphorylation of Akt and ERK as well as the expression of cyclin D1 were decreased (Figure 4D). Together, these results indicated that TACC3 promotes epithelial-mesenchymal transition (EMT) through the activation of PI3K/Akt and ERK signaling pathways in GC cells.
Regulation of epithelial-mesenchymal transition (EMT) factors and altered expression of ERK/Akt/cyclin D1 signaling by the modulation of TACC3 expression in GC cells. (A and B) SNU-638 cells were transfected with Flag (control), Flag-tagged TACC3 plasmids. Forty-eight hours after transfection, the cells were harvested and lysates were prepared and analyzed by immunoblotting using the indicated antibodies. (C and D) AGS cells were transfected with shLuc (control) or TACC3-targeted shRNA (shTACC3) plasmids. Forty-eight hours after transfection, cells were harvested and lysates were prepared and analyzed by immunoblotting using the indicated antibodies.
TACC3 gene expression is upregulated and affects the prognosis of patients with intestinal-type gastric cancer. The role of TACC3 in GC was further assessed by examining the level of TACC3 expression in a GC patient dataset from the Cancer Genome Atlas (TCGA) database published in the Cbioportal (33, 34). Of the 440 identified cases, TACC3 gene expression levels were reported in 412. Of those, data on both histologic type and survival were available for 129 cases. The level of TACC3 gene expression was significantly higher in patients with intestinal-type GC than in patients with diffuse-type GC (p=0.013) (Figure 5A), a finding consistent with our IHC results, which showed that TACC3 expression was higher in intestinal-type GC than in diffuse-type GC (p<0.001) (Figure 5B). A Kaplan–Meier survival analysis in which the median value of TACC3 gene expression was divided by the cut-off showed that in patients with intestinal-type GC, the expression level of TACC3 was a significant determinant of disease-specific survival (DSS) (p=0.017) but not in OS (p=0.212) (Figure 6). In the group consisting of all histological types of GC and in the group with diffuse-type GC, expression levels of TACC3 were not significantly related with either DSS (p=0.392 and p=0.94, respectively) or OS (p=0.243 and p=0.904, respectively) (Figure 6). Moreover, we plotted the Kaplan–Meier survival curves for TACC3 the web-based curator. TACC3 gene expression affected the prognosis of patients with intestinal-type gastric cancer, but not diffuse-type GC regarding OS (Figure 7). Together, TACC3 gene expression is upregulated and affects the prognosis of patients with intestinal-type gastric cancer.
TACC3 expression level in gastric cancer (GC) patients according to tumor histologic type. (A) Based on the TCGA data, levels of TACC3 gene expression were significantly higher in patients with intestinal-type GC than in patients with diffuse-type GC. (B) The IHC analysis of TACC3 expression in our patient cohort showed significant differences between intestinal-type GC and diffuse-type GC.
Analyses of disease-specific survival (DSS) and overall survival (OS) in patients with gastric cancer (GC) of all histologic-types, including intestinal-type and diffuse-type GC, using the TCGA data. (A) All histologic-type GC was not significantly related to a longer DSS. (B, C) Patients with intestinal-type GC whose tumor exhibited low TACC3 expression had a significantly longer DSS, whereas no significant benefit was determined for patients with diffuse-type GC. (D) All histologic-type GC was not significantly related to longer OS. (E, F) Patients with intestinal-type GC and low TACC3 expression by the tumor tended to have a longer DSS but the difference compared to those with high TACC3 expression was not significant. This difference in survival rates became even less significant in the group with diffuse-type GC.
Analysis of overall survival (OS) in patients with gastric cancer (GC) of all histologic-types using the Kaplan–Meier Plotter database. (A and B) All histologic-type GC and Intestinal-type GC were significantly related to a longer OS. (C and D) Patients with diffuse-type GC and mixed-type GC had no significantly longer OS. This difference in survival rates became even less significant in the group with diffuse-type GC.
Discussion
TACC3 is presumably required during the process of cell growth and differentiation (35) but its function also seems to depend on the specific type of cell or organ (27). Oncogenic deregulation of TACC3 has been related to the progression of various human cancers (28) and a TACC3 inhibitor has been tested as a potent anticancer drug (36). In this study, therefore, we investigated the functional impact of TACC3 on GC to determine its clinicopathological relevance. Our results show that over-expression of TACC3 increases the motility and proliferation of GC cells and promotes the EMT, through the ERK/Akt/cyclin D1 signaling pathways, implying a role for this protein in GC progression. We also found an association of enhanced TACC3 expression with decreased DFS and OS, especially in GC patients with the intestinal type (37, 38).
We have reported that TACC3 activates the ERK and PI3K/Akt signaling pathways leading EMT process in cervical cancer (27). Among TACC family proteins, TACC3 is vital in the cellular processes of growth, differentiation, and gene regulation (19). Increased cancer cell proliferation, differentiation, invasion, and metastasis are key elements in carcinogenesis (39), with EMT playing a crucial role in the latter two events (40). A previous study showed a higher invasive capacity of TACC3-over-expressing cells through the support of EMT (41). A role for the snail and slug proteins in EMT during embryogenesis and also in tumor progression has been reported (42). β-catenin, another key cell regulator, has been shown to trigger numerous genes, including cyclin D1, involved in cancer initiation and progression (43, 44). ERK activation is required for EMT processes such as adherent junction loss and acquisition of mesenchymal features by tumor cells (45). ERK signaling increases snail and slug expression in lung cancer (46) while upregulation of the two proteins by β-catenin and Akt/ERK signals in cancer cells leads to downregulation of E-cadherin (47, 48). We also found elevated levels of phosphorylated Akt/ERK and activation of the cyclin D1 signaling pathways in TACC3-over-expressing AGS and SNU-638 GC cells. In contrary, decreased expression of EMT markers was found in TACC3-knockdown cells. These are in accordance with the result of a previous study (28). In summary, our experimental results demonstrate that TACC3 promotes EMT and upregulates the Akt/ERK and cyclin D1 signaling pathways in GC cells.
In patients with GC, higher levels of TACC3 expression by the tumor are associated with a worse prognosis regardless of the histologic type of GC (49). However, in both our cohort and the publicly open dataset TCGA, TACC3 expression was correlated with survival benefit only in patients with intestinal-type GC. Since TACC3 is enhanced in the early stage of differentiation in various cell types and highly expressed in cells undergoing rapid growth and differentiation, the degree of GC differentiation (according to the Lauren classification) may affect survival. In addition to the differential expression of TACC3 in tumor cells vs. the surrounding normal mucosa, TACC3 expression was detected in immune cells within the tumor. Strong labeling of TACC3 in an immune cell population that included lymphocytes, polymorphonuclear leukocytes, and monocytes has been reported (38). The presence of TACC3-positive immune cells may reflect the presence of tumor-infiltrating lymphocytes or a functional role for TACC3 in the immune cell population, but this remains to be determined in further studies. Clinically, high TACC3-positive immune cell counts have been related to a prolonged DFS in patients with intestinal-type and diffuse-type GCs, and in the former, it was shown to be an independent predictor of DFS. Whether the role of TACC3 in molecular signaling pathways differs according to the Lauren type of GC and within the immune cell population also requires further research.
High levels of TACC3 protein have been reported in liver (22), non-small-cell lung (21), colon (50), and cervical cancer (27). The upregulation of TACC3 gene expression during the advance of breast cancer from in situ carcinoma to invasive type implies a role for TACC3 in tumor advancement and in invasive cancer malignancy phenotypes (26). The diverse manifestations of TACC3 expression point to its various roles according to different types of primary tumor while ultimately contributing to carcinogenesis and metastasis, by acting on mitosis and oncogenic signaling and promoting genomic instability (19).
The results of our study imply that TACC3 participates in oncogenic functions in GC cells, including EMT and ERK/Akt/cyclin D1 signaling pathways. Higher expression of TACC3 may be linked to a poor prognosis in patients with intestinal-type—but not diffuse-type—GC. Consequently, TACC3 may be a therapeutic target in GC, but efficacy may depend on the histologic subtype of the tumor.
Acknowledgements
This study was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIP) (2016R1A5A2945889 & 2018 R1D1A1B07050274 for CKK, 2020R1A5A2031185 & 2019R1A2B5B01070598 for LKH), and the Chonnam National University Hwasun Hospital Biomedical Research Institute (HCRI19031 for KSM & KHL).
Footnotes
↵* These Authors contributed equally to this work.
Authors’ Contributions
M.R.A. investigation, writing the original draft; J.S.P. methodology, validation; M.G.N. software, visualization, data curation. G.H.H. formal analysis, investigation. Y.S.P. resources, project administration; J.H.L. supervision, project administration; K.S.M. conceptualization, writing - review & editing; C.K.K. funding acquisition, writing - review & editing; K.H.L. supervision, funding acquisition; writing - review & editing.
Conflicts of Interest
All Authors have no conflicts of interest to disclose in relation to this study.
- Received May 27, 2021.
- Revision received June 14, 2021.
- Accepted June 15, 2021.
- Copyright © 2021 International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.
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