Establishment of a gastric cancer cell line with high microsatellite instability, OCUM-13, derived from Borrmann type-2 primary tumor.

Gastric cancer (GC) with microsatellite instability (MSI) has been reported to be sensitive to immunotherapy, however some of GC cases with MSI remain resistant to immunotherapy. Cancer cell lines showing MSI might be useful for the analysis of mechanisms of immunotherapy, while only a few GC cell lines with MSI are available so far. In this study, we established a unique GC cell line with MSI, OCUM-13, from a primary GC with abundant tumor-infiltrating lymphocytes. MSI assay indicated that OCUM-13 cells as well as the primary tumor showed a band shift in more than 3 of 5 microsatellite loci, suggesting that OCUM-13 did have high MSI. The subcutaneous inoculation of OCUM-13 cells into mice performed tumor formation. Insulin-like growth factor 1 receptor inhibitor decreased the growth of OCUM-13 cells. The newly established cell line with MSI, OCUM-13, might be useful for the analysis of cancer therapy for GC with MSI.

Lipocalin-2 negatively regulates epithelial-mesenchymal transition through matrix metalloprotease-2 downregulation in gastric cancer.

BACKGROUND: Although the role of Lipocalin-2 (LCN2) in cancer development has been focused on recent studies, the molecular mechanisms and clinical relevance of LCN2 in gastric cancer (GC) still remain unclear. METHODS: Transcriptome analysis of GC samples from public human data was performed according to Lauren's classification and molecular classification. In vitro, Western blotting, RT-PCR, wound healing assay and invasion assay were performed to reveal the function and mechanisms of LCN2 in cell proliferation, migration and invasion using LCN2 knockdown cells. Gene set enrichment analysis (GSEA) of GC samples from public human data was analyzed according to LCN2 expression. The clinical significance of LCN2 expression was investigated in GC patients from public data and our hospital. RESULTS: LCN2 was downregulated in diffuse-type GC, as well as in Epithelial-Mesenchymal Transition (EMT) type GC. LCN2 downregulation significantly promoted proliferation, invasion and migration of GC cells. The molecular mechanisms of LCN2 downregulation contribute to Matrix Metalloproteinases-2 (MMP2) stimulation which enhances EMT signaling in GC cells. GSEA revealed that LCN2 downregulation in human samples was involved in EMT signaling. Low LCN2 protein and mRNA levels were significantly associated with poor prognosis in patients with GC. LCN2 mRNA level was an independent prognostic factor for overall survival in GC patients. CONCLUSIONS: LCN2 has a critical role in EMT signaling via MMP2 activity during GC progression. Thus, LCN2 might be a promising therapeutic target to revert EMT signaling in GC patients with poor outcomes.

Dipeptidyl Peptidase-4 from Cancer-associated Fibroblasts Stimulates the Proliferation of Scirrhous-type Gastric Cancer Cells.

BACKGROUND/AIM: Cancer-associated fibroblasts (CAFs) may promote the malignancy of human scirrhous gastric cancer (SGC) cells. We conducted the present study to identify novel growth factors from CAFs. MATERIALS AND METHODS: OCUM-12 and 2 CAF cell lines were used. The proliferation of cancer cells was determined by the number of cancer cells or the MTT assay. The growth factor(s) were purified and characterized by the gel filtration chromatography and protein array. RESULTS: The molecular weight of the growth-stimulating factor was estimated to be approximately 66-669 kDa. Protein array of conditioned medium (CM) from CAFs indicated that dipeptidyl peptidase-4 (DPP-4) was one of the growth factors. The addition of CM increased the phosphorylation of C-X-C chemokine receptor 4 (CXCR4). The DPP-4 inhibitor significantly inhibited the growth-stimulating activity of CM. CONCLUSION: DPP-4 from CAFs might be one of the growth-stimulating factors for SGC through CXCR4.

Gastric cancer stem cells survive in stress environments via their autophagy system.

Cancer stem cells (CSCs) play an important role in the progression of carcinoma and have a high potential for survival in stress environments. However, the mechanisms of survival potential of CSCs have been unclear. The aim of this study was to clarify the significance of autophagy systems of CSCs under stress environments. Four gastric cancer cell line were used. Side population (SP) cells were sorted from the parent cells, as CSC rich cells. The expression of stem cell markers was examined by RT-PCR. The viability of cancer cells under starvation and hypoxia was evaluated. The expression level of the autophagy molecule LC3B-II was examined by western blot. The numbers of autophagosomes and autolysosomes were counted by electron microscope. SP cells of OCUM-12 showed a higher expression of stem cell markers and higher viability in starvation and hypoxia. Western blot and electron microscope examinations indicated that the autophagy was more induced in SP cells than in parent cells. The autophagy inhibitor significantly decreased the viability under the stress environments. These findings suggested that Cancer stem cells of gastric cancer might maintain their viability via the autophagy system. Autophagy inhibitors might be a promising therapeutic agent for gastric cancer.

EMMPRIN in extracellular vesicles from peritoneal mesothelial cells stimulates the invasion activity of diffuse-type gastric cancer cells.

Peritoneal metastasis of gastric cancer (GC) results in extremely poor prognoses. The peritoneal cavity is covered by a monolayer of peritoneal mesothelial cells (PMCs). Interactions between GC cells and PMCs might play a pivotal role in peritoneal metastasis. Extracellular vesicles (EVs) correlate with intercellular communication. Although intercellular communication between cancer cells and PMCs might be associated with the peritoneal metastatic process, the role of EVs from PMCs remains unclear. We investigated the effects of EVs from PMCs on GC cells. Three GC cell lines (OCUM-12, NUGC-3, and MKN74) and four mesothelial cell lines were used. The effects of EVs derived from the PMCs on the invasion and migration of GC cells were evaluated by Matrigel invasion assay. Factors contained in the PMC EVs were analyzed; extra-cellular matrix metalloproteinase inducer (EMMPRIN) was detected in the EVs. The effects of an EMMPRIN inhibitor on the invasion-stimulating activity of EVs were examined. The EMMPRIN expressions of 110 GCs were evaluated by immunohistochemistry. PMC EVs significantly promoted the invasion of diffuse-type GC cells, i.e., OCUM-12 and NUGC-3 cells. EMMPRIN in the EVs stimulated the invasion of OCUM-12 and NUGC-3 cells. The invasion-stimulating activity of PMC EVs was inhibited by the EMMPRIN inhibitor. A high EMMPRIN expression in PMCs was significantly associated with worse cancer-specific survival and peritoneal-recurrence-free survival. EMMPRIN in EVs from PMCs might stimulate the malignant progression of diffuse-type GC. EMMPRIN might be a useful prognostic marker of recurrence in GC patients.

The clinicopathologic significance of Tks5 expression of peritoneal mesothelial cells in gastric cancer patients.

BACKGROUND: Gastric cancer (GC) patients frequently develop peritoneal metastasis. Recently, it has been reported that peritoneal mesothelial cells (PMCs) activated by GC cells acquire a migratory capacity and promote GC cell invasion. The invasiveness of PMCs reportedly depends on the activity of Tks5, an adaptor protein required for invadopodia formation. However, the relationship between clinicopathologic features and Tks5 expression in PMCs has been poorly documented. In this study, we evaluated the clinicopathologic significance of the Tks5 expression of PMCs in GC patients. MATERIALS AND METHODS: A total of 110 GC patients who underwent gastrectomy were enrolled in this study. Tks5 expressions in PMCs from the greater omentum, lesser omentum and retroperitoneum were evaluated by immunohistochemistry. We analyzed the correlation between Tks5 expressions in PMCs and the patients' clinicopathologic features. RESULTS: Tks5 expression was found in 71 (64.5%) of the 110 patients, while 39 (35.5%) were Tks5-negative. Tks5 positivity was significantly (p = 0.038) associated with a greater tumor depth (i.e., T3/4 compared with T1/T2). Peritoneal recurrence was found in 12 of 98 cases within 3 years of surgery. The 3-year peritoneal recurrence-free survival (PRFS) rate in Tks5-positive cases was significantly poorer than that in Tks5-negative cases (80.1% vs 97.4%, p = 0.024). Multivariate analysis revealed that Tks5 positivity and lymph node metastasis were independent factors for PRFS. CONCLUSION: Tks5 is frequently expressed in PMCs in advanced-stage gastric cancer. Tks5 might be a useful predictor for peritoneal recurrence in GC patients.

[Choroidal metastasis from gastric cancer 8 years after surgery].

A man in his 50s underwent total gastrectomy with D2 lymphadenectomy for gastric cancer 8 years ago. The pathological stage was pT3N3bM0, pStage IIIC. He took tegafur, gimeracil, and oteracil potassium (S-1) as adjuvant chemotherapy for the next 3 years at his own request. No recurrence was observed for 8 years after surgery, but then a recurrent lesion near the anastomosis and multiple metastases were detected on abdominal computed tomography. He started treatment with S-1 plus oxaliplatin. One month later, he experienced right-sided visual disturbance. Ophthalmological tests revealed a tumor on his choroid. Three months later, the recurrent tumor and metastatic lesions shrank, and his visual symptoms improved. Therefore, we diagnosed choroidal metastasis from gastric cancer. Choroidal metastasis from the gastrointestinal tract is extremely rare. We discuss this case along with the relevant literature.

[Laparoscopic Surgical Treatment of Differentiated Intramucosal Gastric Cancer with Lymph Node Metastasis-A Case Report].

A 78‒year‒old man was admitted to our hospital with the chief complaint of 5 kg weight loss in 6 months. An esophagogastroduodenoscopy revealed a 0‒Ⅱa lesion in the posterior wall of the antrum, and biopsy findings showed a well‒differentiated adenocarcinoma. Endoscopic ultrasonography did not show an obvious invasion of the submucosal layer. Contrast‒ enhanced abdominal computed tomography(CT)revealed an enlargement of the #11p lymph node to approximately 30 mm, and positron emission tomography(PET)‒CT showed an accumulation in the same lymph node. Since no other apparent distant metastases were observed, laparoscopic distal gastrectomy and D2 dissection were performed. The postoperative pathological diagnosis was L, 7×8 mm, 0‒Ⅱa, tub1, pT1a, ly0, v0, pPM0(73 mm), pDM0(35 mm), N2, and pStage ⅡA. We report this case because the successful laparoscopic resection of a differentiated gastric mucosal cancer with lymph node metastasis has been considered to be extremely rare.

[A Case of Long-Term Survival after Multidisciplinary Treatment for Neuroendocrine Carcinoma of the Anal Canal].

A 75-year-old man presented to a local clinic with anal pain, and a palpable anal tumor on was found on digital examination of the rectum. A biopsy led to the diagnosis of neuroendocrine carcinoma. Besides the anal tumor, an right-inguinal lymph node was revealed on computed tomography(CT). Positron emission tomography-CT showed abnormal uptake in the 2 regions. He was diagnosed with lymph node metastases from anal canal carcinoma, and an abdominoperineal resection was performed. The resected specimen included the anal canal tumor with a size of 27×18 mm in diameter. On immunohistochemistry, the anal canal tumor was strongly positive for synaptophysin and positive for chromogranin A, with a Ki- 67 positivity index of 70%. After the surgery, he was administered chemotherapy with 4 courses of cisplatin and CPT-11. One year after the surgery, CT revealed lymph node recurrence. Therefore, cisplatin and CPT-11 therapy was repeated. After 11 courses of the cisplatin and CPT-11 treatment, tumor regrowth was still detected. The treatment protocol was changed to an amrubicin monotherapy regimen. However, the patient's general condition worsened after the therapies, and he died 38 months after the surgery.

[A Case of Long-Term Survival after Chemotherapy for Gastric Cancer with Peritoneal Dissemination].

The patient was a 58-year-old man who had undergone wide gastrectomy for gastric ulcer at 22 years of age. Endoscopic examination revealed an advanced type 3 gastric cancer in the anastomotic region. We performed total gastrectomy and D1 lymph node dissection because of the bleeding from the tumor, although peritoneal dissemination was found during the surgery. A post-operative pathological diagnosis of gastric cancer pT4b(SI, abdominal wall)N0M1(PER), pStage Ⅳ, was made. After the surgery, he was administered chemotherapy with S-1 and cisplatin. After 9 courses of the treatment, the treatment protocol was changed to an S-1 therapy regimen because of general fatigue. Four years and 8 months after the surgery, the tumor marker had increased, and CT scans revealed a dissemination nodule at the left back side of the bladder. Therefore, PTX plus Rmab therapy was administered as a second-line chemotherapy. Treatment with PTX plus Rmab resulted in tumor reduction, with an improvement of the QOL of the patient; partial response was maintained for 12 months. After 16 courses of the PTX plus Rmab treatment, tumor regrowth was detected. The treatment protocol was changed again to a nivolumab regimen. After 4 courses, the tumor marker was normalized, and CT scans revealed that the peritoneal dissemination had shrunk. Although the prognosis of gastric cancer with dissemination is very poor, it is possible to prolong survival with chemotherapy.

Clinical difference between fibroblast growth factor receptor 2 subclass, type IIIb and type IIIc, in gastric cancer.

Fibroblast growth factor receptor 2 (FGFR2) has two isoforms: IIIb type and IIIc type. Clinicopathologic significance of these two FGFR2 subtypes in gastric cancer remains to be known. This study aimed to clarify the clinicopathologic difference of FGFR2IIIb and/or FGFR2IIIc overexpression. A total of 562 patients who underwent gastrectomy was enrolled. The expressions of FGFR2IIIb and FGFR2IIIc were retrospectively examined by immunohistochemistry or fluorescence in situ hybridization (FISH) using the 562 gastric tumors. We evaluated the correlation between clinicopathologic features and FGFR2IIIb overexpression and/or FGFR2IIIc overexpression in gastric cancer. FGFR2IIIb overexpression was observed in 28 cases (4.9%), and FGFR2IIIc overexpression was observed in four cases (0.7%). All four FGFR2IIIc cases were also positive for FGFR2IIIb, but not in the same cancer cells. FGFR2IIIb and/or FGFR2IIIc overexpression was significantly correlated with lymph node metastasis and clinical stage. Both FGFR2IIIb and FGFR2IIIc were significantly associated with poor overall survival. A multivariate analysis showed that FGFR2IIIc expression was significantly correlated with overall survival. FISH analysis indicated that FGFR2 amplification was correlated with FGFR2IIIb and/or FGFR2IIIc overexpression. These findings suggested that gastric tumor overexpressed FGFR2IIIc and/or FGFR2IIIb at the frequency of 4.9%. FGFR2IIIc overexpression might be independent prognostic factor for patients with gastric cancer.

Circulating CEA-positive and EpCAM-negative tumor cells might be a predictive biomarker for recurrence in patients with gastric cancer.

It has been reported that circulating tumor cells (CTCs) are beneficial for predicting tumor stage or treatment response. Although epithelial cell adhesion molecules (EpCAMs) and cytokeratin (CK) have been often used for the identification of CTCs, other tumor markers have not been fully investigated as detecting tools for CTCs. Thus, this study aims to clarify the significance of carcinoembryonic antigen (CEA, CD66e)-positive CTCs in patients with gastric cancer. A total of 150 patients with gastric cancer were enrolled in this study. The mononuclear fraction of peripheral blood was enriched by Ficoll. The number of cells was enumerated depending on the positivity of EpCAM and CEA or CK by flow cytometry. The association of these cells with clinicopathologic characteristics was investigated. The mean age was 70 (range 28-92). The macroscopic type of gastric cancer was classified as 0/1/2/3/4/5 in 59/11/22/38/16/4 patients, respectively. Seventy-one patients (47.3%) were diagnosed with intestinal-type cancer, while 76 patients (50.7%) were diagnosed with the diffuse type. The mean numbers of cells with EpCAM-CK+, EpCAM+CK-, EpCAM+CK+, EpCAM-CEA+, EpCAM+CEA-, and EpCAM+CEA+ were 618, 237, 19.9, 1147, 291, and 7.41, respectively. The number of EpCAM-CEA+cells was significantly higher in patients with stage II-III and IV than in patients with stage I. The 3-year RFS rate in patients with a high number of EpCAM-CEA+cells (>=622) was 57.5%, while it was 79.3% in patients with a low number of EpCAM-CEA+cells (<622) (log-rank p = 0.0079). Thus, we conclude that CEA-positive CTCs will be a clinically beneficial biomarker in patients with gastric cancer.

Circulating tumor cells with FGFR2 expression might be useful to identify patients with existing FGFR2-overexpressing tumor.

Fibroblast growth factor receptor (FGFR) is associated with proliferation, migration, and angiogenesis of carcinomas, and FGFR signaling inhibitors are considered a key drug for the treatment of solid tumors with FGFR overexpression. Amplification of FGFR2 is reportedly identified in 3%-10% of gastric cancers (GCs). The aim of this study is to clarify whether the identification of the circulating tumor cells (CTCs) with FGFR2 overexpression is useful to detect patients with FGFR2-overexpressing GC. One hundred GC patients who underwent gastrectomy were enrolled. A total volume of 8 mL of peripheral blood was collected from each patient just before gastrectomy, and mononuclear cells were enriched by Ficol density gradient centrifugation. These cells were immunostained with PI/CD45/EpCAM/FGFR2. The number of CTCs with FGFR2 expression in each sample was enumerated by FACScan. The FGFR2 expression level of the resected primary tumor was assessed by immunohistochemistry. The number of FGFR2-positive CTCs in the GC patients' peripheral blood was significantly correlated with the FGFR2 expression level of the primary GC. The relapse-free survival of the patients with FGFR2-positive CTCs (≥5 cells/10 mL blood) was significantly poorer (P = .018, log-rank) than that of the patients without FGFR2-positive CTCs (<5 cell/10 mL blood). These findings suggested that the determination of FGFR2-positive CTCs might help identify an existing tumor with FGFR2 overexpression.

[A Case of HER2-Positive Gastric Cancer with Multiple Liver Metastases Treated with Curative Conversion Therapy after Chemotherapy].

A 66-year-old man underwent chemotherapy with S-1 plus cisplatin plus trastuzumab to treat advanced gastric cancer that was diagnosed as cStage Ⅳ adenocarcinoma(T3N1M1[P0, CYX, H1]). After 8 courses, liver metastases were absent on contrast-enhanced MRI. The patient underwent a laparoscopic distal gastrectomy with D2 lymphadenectomy. The gross appearance of the surgically resected specimen showed a shrunk gastric tumor measuring 1 mm. The postoperative course was uneventful, and the patient has been well, receiving maintenance chemotherapy of S-1 plus trastuzumab without evidence of recurrence for 15 months following the operation. Conversion surgery following chemotherapy might be an effective treatment for patients with advanced gastric cancer; however, further studies are needed to establish this treatment strategy.

Correction: Microscopic distance from tumor invasion front to serosa might be a useful predictive factor for peritoneal recurrence after curative resection of T3-gastric cancer.

[This corrects the article DOI: 10.1371/journal.pone.0225958.].

Serine threonine kinase 11/liver kinase B1 mutation in sporadic scirrhous-type gastric cancer cells.

Scirrhous-type gastric carcinoma (SGC), which is characterized by the rapid proliferation of cancer cells accompanied by extensive fibrosis, shows extremely poor survival. A reason for the poor prognosis of SGC is that the driver gene responsible for SGC has not been identified. To identify the characteristic driver gene of SGC, we examined the genomic landscape of six human SGC cell lines of OCUM-1, OCUM-2M, OCUM-8, OCUM-9, OCUM-12 and OCUM-14, using multiplex gene panel testing by next-generation sequencing. In this study, the non-synonymous mutations of serine threonine kinase 11/liver kinase B1 (STK11/LKB1) gene were detected in OCUM-12, OCUM-2M and OCUM-14 among the six SGC cell lines. Capillary sequencing analysis confirmed the non-sense or missense mutation of STK11/LKB1 in the three cell lines. Western blot analysis showed that LKB1 expression was decreased in OCUM-12 cells and OCUM-14 cells harboring STK11/LKB1 mutation. The mammalian target of rapamycin (mTOR) inhibitor significantly inhibited the proliferation of OCUM-12 and OCUM-14 cells. The correlations between STK11/LKB1 expression and clinicopathologic features of gastric cancer were examined using 708 primary gastric carcinomas by immunochemical study. The low STK11/LKB1 expression group was significantly associated with SGC, high invasion depth and frequent nodal involvement, in compared with the high STK11/LKB1 expression group. Collectively, our study demonstrated that STK11/LKB1 mutation might be responsible for the progression of SGC, and suggested that mTOR signaling by STK11/LKB1 mutation might be one of therapeutic targets for patients with SGC.

Microscopic distance from tumor invasion front to serosa might be a useful predictive factor for peritoneal recurrence after curative resection of T3-gastric cancer.

BACKGROUND: Peritoneal recurrence is one of the most frequent recurrent diseases in gastric cancer. Although the exposure of cancer cells to the serosal surface is considered a common risk factor for peritoneal recurrence, there are some cases of peritoneal recurrence without infiltration to the serosal surface even after curative surgery. This study sought to clarify the risk factors of peritoneal recurrence in the absence of invasion to the serosal surface. MATERIALS AND METHODS: Ninety-six patients with gastric cancer who underwent curative surgery were enrolled. In all 96 cases, the depth of tumor invasion was subserosal (T3). The microscopic distance from the tumor invasion front to the serosa (DIFS) was measured using tissue slides by H&E staining and pan-cytokeratin staining. E-cadherin expression was evaluated by immunohistochemical staining. RESULTS: Among the 96 patients, 16 developed peritoneal recurrence after curative surgery. The DIFS of the tumors with peritoneal recurrence (156±220 µm) was significantly shorter (p = 0.011) than that without peritoneal recurrence (360±478 µm). Peritoneal recurrence was significantly correlated with DIFS ≤234 µm (p = 0.023), but not with E-cadherin expression. The prognosis of DIFS ≤234 µm was significantly poorer than that of DIFS >234 µm (log rank, p = 0.007). A multivariate analysis of the patients' five-year overall survival revealed that DIFS ≤234 µm and lymph node metastasis were significantly correlated with survival (p = 0.005, p = 0.032, respectively). CONCLUSION: The measurement of the DIFS might be useful for the prediction of peritoneal recurrence in T3-gastric cancer patients after curative surgery.

[A Case of Hypophysitis Due to Immune Check Point Inhibitor Treatment].

The patient was a man in his 70s with bone metastasis from renal cell carcinoma who had received immune checkpoint inhibitors(ICI)therapy. After 2 courses of chemotherapy, he was admitted to our hospital with diverticulitis. His diverticulitis could be treated with antibiotics, but he presented with severe hyponatremia and consciousness disorder during hospitalization. Brain MRI showed pituitary swelling, and his serum TSH, ACTH, cortisol levels decreased. We therefore diagnosed him with hypopituitarism due to ICIs. Hydrocortisone improved his hyponatremia and consciousness disorder. Endocrine stimulation tests revealed no reaction of ACTH, and low-level reactions of TSH, LH and FSH, ICIs cause many types of immune- related adverse events(irAEs). The indications for ICI therapy are expanding; thus, we can expect to experience more cases of serious irAEs in association with ICI treatment. Further studies should be performed to improve our understanding of irAEs.

The Clinicopathological Significance of the CXCR2 Ligands, CXCL1, CXCL2, CXCL3, CXCL5, CXCL6, CXCL7, and CXCL8 in Gastric Cancer.

BACKGROUND/AIM: We have previously reported that chemokine (C-X-C motif) receptor 2 (CXCR2) signaling was associated with the malignant progression of gastric cancer (GC). We thus examined the clinicopathological significance of CXCR2 ligands, CXCL1, CXCL2, CXCL3, CXCL5, CXCL6, CXCL7, and CXCL8, in GC. PATIENTS AND METHODS: The expression of CXCR2 ligands in 590 GC cases was investigated by immunohistochemistry. RESULTS: The expression was as follows: CXCL1, 46.2% (257/557); CXCL2, 20.7% (122/590); CXCL3, 17.1% (101/589); CXCL5/CXCL6, 2.9% (17/589); CXCL7, 36.4% (215/590); and CXCL8 1.7% (10/585) of the cases. High invasion depth was correlated with CXCL1 expression. Lymph node metastasis and peritoneal cytology positivity were correlated with high expression of CXCL1 and CXCL7. The prognoses of the CXCL1-positive patients were significantly poorer than those of the CXCL1-negative patients (p<0.001). CONCLUSION: Among the CXCR2 ligands, CXCL7 and especially CXCL1, might play an important role in the malignant progression of GC via CXCR2 signaling.

The clinicopathological significance of Thrombospondin-4 expression in the tumor microenvironment of gastric cancer.

INTRODUCTION: Thrombospondin-4 [1] is an extracellular glycoprotein involved in wound healing and tissue remodeling. Although THBS4 is reportedly frequently expressed in solid tumors, there are few reports of the clinicopathological features of carcinomas with THBS4 expression. We evaluated the clinicopathologic significance of THBS4 expression in gastric carcinoma (GC). MATERIALS AND METHODS: We retrospectively analyzed the cases of 584 GC patients. The expression of THBS4 in each tumor was evaluated by immunohistochemistry. We then divided the patients into the THBS4-high (n = 223, 38.2%) group and THBS4-low (n = 361, 61.8%) group. THBS4 expression in cancer-associated fibroblasts (CAFs), normal-associated fibroblasts (NFs) and gastric cancer cell lines was examined by western blotting. RESULTS: THBS4 is expressed on stromal cells with αSMA or Podoplanin expression in the GC microenvironment, but not expressed on cancer cells with cytokeratin expression. The western blot analysis results showed that CAFs (but not NFs and cancer cells) expressed THBS4. Compared to the THBS4-low expression status, the THBS4-high expression status was correlated with higher αSMA expression, higher invasion depth, lymph-node metastasis, lymphatic invasion, peritoneal cytology, peritoneal metastasis, larger tumor size, microscopic diffuse type, and the macroscopic diffuse infiltrating type. The THBS4-high group's 5-year overall survival rate was significantly poorer than that of the THBS4-low group. A multivariate analysis revealed that THBS4 expression was an independent prognostic factor. CONCLUSION: THBS4 is expressed on CAFs in the gastric cancer microenvironment. THBS4 from CAFs is associated with the metastasis of cancer cells, and is a useful prognostic indicator for gastric cancer patients.