The role of the CCL22-CCR4 axis in the metastasis of gastric cancer cells into omental milky spots

Engineering Biomaterials to Model Immune-Tumor Interactions In Vitro

Engineered biomaterial scaffolds are becoming more prominent in research laboratories to study drug efficacy for oncological applications in vitro, but do they have a place in pharmaceutical drug screening pipelines? The low efficacy of cancer drugs in phase II/III clinical trials suggests that there are critical mechanisms not properly accounted for in the pre-clinical evaluation of drug candidates. Immune cells associated with the tumor may account for some of these failures given recent successes with cancer immunotherapies; however, there are few representative platforms to study immune cells in the context of cancer as traditional 2D culture is typically monocultures and humanized animal models have a weakened immune composition. Biomaterials that replicate tumor microenvironmental cues may provide a more relevant model with greater in vitro complexity. In this review, the authors explore the pertinent microenvironmental cues that drive tumor progression in the context of the immune system, discuss how these cues can be incorporated into hydrogel design to culture immune cells, and describe progress toward precision oncological drug screening with engineered tissues.

Efficacy of anti-programmed cell death protein 1 monoclonal antibody combined with bevacizumab and/or Pseudomonas aeruginosa injection in transplanted tumor of mouse forestomach carcinoma cell gastric cancer in mice and its mechanism in regulating tumor immune microenvironment

Tumor immunotherapy represented by programmed cell death protein 1 (PD-1) inhibitors is considered as the most promising cancer treatment method and has been widely used in the treatment of advanced gastric cancer (GC). However, the effective rate of PD-1 inhibitor monotherapy is low. In this study, we constructed a transplanted tumor model in GC mice by inoculating mouse forestomach carcinoma cell (MFC) GC cells into 615 mice. Interventions were conducted with normal saline, anti-PD-1 monoclonal antibody (mAb), bevacizumab, Pseudomonas aeruginosa-mannose-sensitive hemagglutinin (PA-MSHA), anti-PD-1 mAb combined with bevacizumab, anti-PD-1 mAb combined with PA-MSHA, bevacizumab combined with PA-MSHA, anti-PD-1 mAb combined with bevacizumab and PA-MSHA, respectively. The tumor growth curves were drawn. TUNEL assay, western blotting, and immunohistochemistry were used to detect tumor proliferation and apoptosis. Flow cytometry and ELISA were used to detect the expression of tumor infiltrating lymphocytes and cytokines. This study found that anti-PD-1 mAb alone could not significantly inhibit the growth of transplanted tumors in mice. Anti-PD-1 mAb combined with bevacizumab, anti-PD-1 mAb combined with PA-MSHA, anti-PD-1 mAb combined with bevacizumab and PA-MSHA could all significantly inhibit tumor growth in mice, and the combination of three drugs presented the highest tumor inhibition rate. Anti-PD-1 mAb combined with bevacizumab and PA-MSHA could significantly upregulate the number of Th1-type cells, CD8 + T cells, and Type I tumor-associated macrophages (TAMs), while downregulate the number of Th2-type cells, myeloid-derived suppressor cells, regulatory T cells, and Type II TAMs. Therefore, we conclude that anti-PD-1 mAb combined with bevacizumab and/or PA-MSHA has a synergistic effect. Bevacizumab and PA-MSHA can transform the tumor immunosuppressive microenvironment into a supportive immune microenvironment, thus maximizing the antitumor effect of anti-PD-1 mAb.

Development of the Peritoneal Metastasis: A Review of Back-Grounds, Mechanisms, Treatments and Prospects

Peritoneal metastasis is a malignant disease which originated from several gastrointestinal and gynecological carcinomas and has been leading to a suffering condition in patients for decades. Currently, as people have gradually become more aware of the severity of peritoneal carcinomatosis, new molecular mechanisms for targeting and new treatments have been proposed. However, due to the uncertainty of influencing factors involved and a lack of a standardized procedure for this treatment, as well as a need for more clinical data for specific evaluation, more research is needed, both for preventing and treating. We aim to summarize backgrounds, mechanisms and treatments in this area and conclude limitations or new aspects for treatments.

Tumor microenvironment antigens

The identification and characterization of tumor antigens are central objectives in developing anti-cancer immunotherapy. Traditionally, tumor-associated antigens (TAAs) are considered relatively restricted to tumor cells (i.e., overexpressed proteins in tumor cells), whereas tumor-specific antigens (TSAs) are considered unique to tumor cells. Recent studies have focused on identifying patient-specific neoantigens, which might be highly immunogenic because they are not expressed in normal tissues. The opposite strategy has emerged with the discovery of anti-regulatory T cells (anti-Tregs) that recognize and attack many cell types in the tumor microenvironment, such as regulatory immune cells, in addition to tumor cells. The term proposed in this review is "tumor microenvironment antigens" (TMAs) to describe the antigens that draw this attack. As therapeutic targets, TMAs offer several advantages that differentiate them from more traditional tumor antigens. Targeting TMAs leads not only to a direct attack on tumor cells but also to modulation of the tumor microenvironment, rendering it immunocompetent and tumor-hostile. Of note, in contrast to TAAs and TSAs, TMAs also are expressed in non-transformed cells with consistent human leukocyte antigen (HLA) expression. Inflammation often induces HLA expression in malignant cells, so that targeting TMAs could additionally affect tumors with no or very low levels of surface HLA expression. This review defines the characteristics, differences, and advantages of TMAs compared with traditional tumor antigens and discusses the use of these antigens in immune modulatory vaccines as an attractive approach to immunotherapy. Different TMAs are expressed by different cells and could be combined in anti-cancer immunotherapies to attack tumor cells directly and modulate local immune cells to create a tumor-hostile microenvironment and inhibit tumor angiogenesis. Immune modulatory vaccines offer an approach for combinatorial therapy with additional immunotherapy including checkpoint blockade, cellular therapy, or traditional cancer vaccines. These combinations would increase the number of patients who can benefit from such therapeutic measures, which all have optimal efficiency in inflamed tumors.

Triple-negative breast cancer influences a mixed M1/M2 macrophage phenotype associated with tumor aggressiveness

Triple-negative breast cancer (TNBC) is characterized by excessive accumulation of tumor-infiltrating immune cells, including tumor-associated macrophages (TAMs). TAMs consist of a heterogeneous population with high plasticity and are associated with tumor aggressiveness and poor prognosis. Moreover, breast cancer cells can secrete factors that influence TAM polarization. Therefore, this study aimed to evaluate the crosstalk between cancer cells and macrophages in the context of TNBC. Cytokine-polarized M2 macrophage were used as control. Distinct from the classical M2 macrophage, TAMs generated from TNBC-conditioned media upregulated both M1- and M2-associated genes, and secreted both the anti-inflammatory cytokine interleukin IL-10 and the proinflammatory cytokine IL-6 and tumor necrosis factor- α. Theses TNBC-induced TAMs exert aggressive behavior of TNBC cells. Consistently, TCGA and MTABRIC analyses of human breast cancer revealed upregulation of M1- associated genes in TNBC comparing with non-TNBC. Among these M1-associated genes, CXCL10 and IL1B were revealed to be independent prognostic factors for disease progression. In conclusion, TNBC cells induce macrophage polarization with a mixture of M1 and M2 phenotypes. These cancer-induced TAMs further enhance tumor cell growth and aggressiveness.

Molecular Mechanisms and Potential Rationale of Immunotherapy in Peritoneal Metastasis of Advanced Gastric Cancer

Peritoneal metastasis (PM) is one of the most frequent metastasis patterns of gastric cancer (GC), and the prognosis of patients with PM is very dismal. According to Paget’s theory, disseminated free cancer cells are seeded and survive in the abdominal cavity, adhere to the peritoneum, invade the subperitoneal tissue, and proliferate through angiogenesis. In these sequential processes, several key molecules are involved. From a therapeutic point of view, immunotherapy with chemotherapy combination has become the standard of care for advanced GC. Several clinical trials of newer immunotherapy agents are ongoing. Understanding of the molecular process of PM and the potential rationale of immunotherapy for PM treatment is necessary. Beyond understanding of the molecular aspect of PM, many studies have been conducted on the modality of treatment of PM. Notably, intraperitoneal approaches, including chemotherapy or immunotherapy, have been conducted, because systemic treatment of PM has limitations. In this study, we reviewed the molecular mechanisms and immunologic aspects of PM, and intraperitoneal approaches under investigation for treating PM.

Integration of Genomic Biology Into Therapeutic Strategies of Gastric Cancer Peritoneal Metastasis

The peritoneum is a common site of metastasis in advanced gastric cancer (GC). Diagnostic laparoscopy is now routinely performed as part of disease staging, leading to an earlier diagnosis of synchronous peritoneal metastasis (PM). The biology of GCPM is unique and aggressive, leading to a dismal prognosis. These tumors tend to be resistant to traditional systemic therapy, and yet, this remains the current standard-of-care recommended by most international clinical guidelines. As this is an area of unmet clinical need, several translational studies and clinical trials have focused on addressing this specific disease state. Advances in genomic sequencing and molecular profiling have revealed several promising therapeutic targets and elucidated novel biology, particularly on the role of the surrounding tumor microenvironment in GCPM. Peritoneal-specific clinical trials are being designed with a combination of locoregional therapeutic strategies with systemic therapy. In this review, we summarize the new knowledge of cancer biology, advances in surgical techniques, and emergence of novel therapies as an integrated strategy emerges to address GCPM as a distinct clinical entity.

circ_0004140 promotes LUAD tumor progression and immune resistance through circ_0004140/miR-1184/CCL22 axis

Lung adenocarcinoma (LUAD) is a highly prevalent cancer with high mortality. Immune resistance and tumor metastasis are the pivotal factors for the promotion of LUAD. CircRNAs have been revealed a crucial pre-clinical diagnostic and therapeutic potentials in LUAD. Herein, we identify a novel circRNA (circ_0004140), derived from the oncogene YAP1, which is up-regulated in LUAD. The high expression of circ_0004140 is correlated with poor prognosis and CTL cells dysfunction in LUAD patients. Knockdown of circ_0004140 regulated LUAD cells proliferation, migration, and apoptosis. Mechanistically, circ_0004140 served as a sponge of miR-1184 targeting C-C motif chemokine ligand 22(CCL22). Overexpression of CCL22 reversed the inhibitory effect induced by si-circ_0004140 on cells proliferation and migration. Moreover, we also revealed that elevated circ_ooo4140 was related to cytotoxic lymphocyte exhaustion, and a combination therapy of C-021 (CCL22/CCR4 axis inhibitor) and anti-PD-1 attenuated LUAD promotion and immune resistance. In conclusion, circ_0004140 may drive resistance to anti-PD-1 immunotherapy, providing a novel potential therapeutic target for LUAD treatment.

LncRNA HOTAIR promotes proliferation, invasion and migration in NSCLC cells via the CCL22 signaling pathway

Long noncoding RNA (LncRNA) is a new type of regulatory RNA. LncRNA HOX antisense intergenic RNA (HOTAIR), as an oncogene in non-small cell lung cancer (NSCLC), is one of the key determinants of tumor progression. However, its possible molecular mechanism and the immunomodulatory pathway involved in NSCLC are still unclear. This study aims to explore whether HOTAIR promotes proliferation, migration and invasion of the NSCLC cells by inhibiting the expression of C-C Motif Chemokine Ligand 22 (CCL22). We collected 30 clinical samples of cancer and adjacent normal tissues from the patients with NSCLC, using real-time quantitative polymerase chain reaction (RT-qPCR) to detect the LncRNA HOTAIR and CCL22 mRNA expression in tissues. Immunohistochemistry was used to detect the protein expression of CCL22 in cancer and adjacent normal tissues. Cell experiments were conducted to verify that LncRNA HOTAIR regulates the expression of CCL22 and participates in the progress of NSCLC. The antisense oligonucleotide (ASO) probe interfering with LncRNA HOTAIR and the interference fragment of CCL22 (si-CCL22) were constructed. A549 cells were co-transfected with ASO-HOTAIR and si-CCL22. We used RT-qPCR to detect the expression of LncRNA HOTAIR and CCL22 mRNA in the cells, enzyme-linked immunosorbent assay (ELISA) used to detect the CCL22 protein level in the cell supernatant. 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay was applied to detect cell proliferation, the Flow cytometry to detect cell apoptosis. Finally, the Transwell test was utilized to detect cell migration and invasion. In conclusion, this study suggests that HOTAIR may promote proliferation, migration and invasion of the NSCLC cells by inhibiting CCL22 expression, which may play a key role in NSCLC cell immunity.

Macrophages play a role in inflammatory transformation of colorectal cancer

Colorectal cancer (CRC) is one of the most common and fatal cancers worldwide, and it is also a typical inflammatory cancer. The function of macrophages is very important in the tissue immune microenvironment during inflammatory and carcinogenic transformation. Here, we evaluated the function and mechanism of macrophages in intestinal physiology and in different pathological stages. Furthermore, the role of macrophages in the immune microenvironment of CRC and the influence of the intestinal population and hypoxic environment on macrophage function are summarized. In addition, in the era of tumor immunotherapy, CRC currently has a limited response rate to immune checkpoint inhibitors, and we summarize potential therapeutic strategies for targeting tumor-associated macrophages.

Gastrectomy with omentum preservation versus gastrectomy with omentectomy for locally advanced gastric cancer: A systematic review and meta-analysis

BACKGROUND

Omentectomy has been traditionally a part of standard radical gastrectomy. Its clinical benefit for locally advanced gastric cancer (LAGC) remains controversial. This study aimed at evaluating the impact of gastrectomy with omentum preservation (GOP) on survival, recurrence, surgical outcomes and postoperative complications by comparing with gastrectomy with omentum resection (GOR).

METHODS

Original studies comparing GOP with GOR in LAGC were searched. Meta-analysis was performed using RevMan 5.4.

RESULTS

Seven studies involving 1879 patients were analyzed. Compared with GOR, GOP achieved significantly better overall survival (HR = 0.75 [0.60, 0.95], P = 0.01), with similar relapse-free survival (HR = 0.84 [0.68, 1.03], P = 0.10). The two groups had similar total recurrence rate (OR = 0.86 [0.68, 1.08], P = 0.19) and no significant differences in rates of peritoneal, hematogenous, locoregional or distant lymph node recurrences. GOP had significantly less blood loss (MD = -83 [-139, -28] ml, P = 0.003) and tended to have shorter operation time (MD = -28 [-58, 2] min, P = 0.06), with similar harvested number of lymph nodes (MD = -0.4 [-2.6, 1.8], P = 0.70). The incidences of total all grade and major complications were similar in GOP and GOR (all grade: 31.8% vs. 30.3%, OR = 1.08 [0.79, 1.46], P = 0.64; major: 9.2% vs. 10.1%, OR = 1.14 [0.55, 2.34], P = 0.73). There were no significant differences in incidences of complication or postoperative mortality.

CONCLUSIONS

Omentum preservation did not affect curability or survival in LAGC. These findings require validation in randomized controlled trials with large sample sizes.

CCL17 and CCL22 induce CCR4 receptor expression and promote cytokine-induced killer cells migration

Recently, cytokine-induced killer (CIK) cells have been shown to possess effective cytotoxic activity against some tumor cells both in vitro and in clinical research. Furthermore, dendritic cell-activated CIK (DC-CIK) cells display significantly increased antitumor activity compared to unstimulated CIK cells. Study findings indicate DC cells can secrete chemokine C-C motif ligand 17 (CCL17) and chemokine C-C motif ligand 22 (CCL22) with a common receptor molecule, C-C chemokine receptor type-4(CCR4). CCL17 and CCL22 levels were measured by ELISA from CIK cell culture supernatants and the expression of CCR4 on CIK and DC-CIK cells was analyzed by flow cytometry. Through Migration and Killing assays, further analyzed the effects of the altered expression levels of CCR4 on the chemotactic ability and the tumor-killing efficiency of CIK cells. We found markedly increased CCL17 and CCL22 in supernatants of DC-CIK co-cultures. Similarly, the expression of CCR4 was also increased on CIK cells in these co-cultures. Further, the stimulation of CCL17 and CCL22 increased expression of the CCR4 and enhanced the migratory capacity and antitumor efficacy of CIK cells. Simultaneously, similar effects had achieved by transfecting the CCR4 gene into CIK cells. DC cells may promote the expression of CCR4 on CIK cells by secreting CCL17 and CCL22, thereby promoting infiltration of DC-CIK cells into the tumor microenvironment, and exerting stronger antitumor activity than CIK cells.

Pentraxin-3 inhibits milky spots metastasis of gastric cancer by inhibiting M2 macrophage polarization

Purpose: Recent studies have indicated that Pentraxin-3 (PTX3) is related to invasion, migration and metastasis of gastric cancer cells (GCCs). However, the function of PTX3 in stemness and tumor-associated macrophages (TAMs) polarization in GC has not yet been revealed. Here, we investigated the role of PTX3 in TAMs polarization and stemness in gastric cancer (GC), and further explored the effect of PTX3 on milky spot metastasis of gastric cancer.

Methods: PTX3 expression in human gastric cancer tissues was examined with immunohistochemistry (IHC). The influence on stemness of gastric cancer cells was examined by sphere formation assay and western blot. qRT-PCR, IHC and flow cytometry were used to evaluate M1/M2 macrophage signatures. The effects of PTX3 on TAM polarization and milky spots were investigated in vitro and in vivo. The possible mechanism of PTX3 on targeted cytokines and pathway were analyzed by qRT-PCR and western blot.

Results: We found that PTX3 was low expressed in gastric carcinoma tissues and associated with stemness and polarization of macrophages. The upregulation of PTX3 inhibited the stemness of GCCs. Furthermore, PTX3 suppressed the polarization of M2 macrophages in the milky spots in vivo and in vitro and inhibited the metastasis of GC into milky spots. PTX3 restrained the expression of interleukin-4 (IL-4) and IL-10 via the inhibition of phosphorylation of the c-Jun N-terminal protein kinase 1/2 (JNK1/2) in GCCs.

Conclusion: These results revealed a novel mechanism of PTX3 in GC, which may participate in the development and metastasis of GC by affecting stemness and macrophage polarization. PTX3 should be considered as a crucial biomarker and may be potentially used in targeted therapy in GC progression.

E2F2 stimulates CCR4 expression and activates synovial fibroblast-like cells in rheumatoid arthritis

Aim of the study

E2F transcription factor 2 (E2F2) has increased expression in synovial tissues of rheumatoid arthritis (RA) and stimulates interleukin (IL)-1 α and IL-β production in cultured RA synovial fibroblast-like cells (RASF), which supports the importance of E2F2 in RA pathogenesis. This study investigated the effect and mechanism of E2F2 in RA.

Material and methods

Cultured RASF were transfected with anti-E2F2 siRNA, and the expression profile was analyzed with an inflammatory response and autoimmunity PCR array loaded with 84-relative genes to explore the pathogenic pathway of E2F2. Apoptosis, migration and tube-like structure formation in the RASF with transfection of anti-E2F2 siRNA or E2F2-expressing plasmids were examined using flow cytometry, transwell assays and Matrigel assays, respectively.

Results

Significantly decreased expression of chemokine receptor 4 (CCR4) was detected in RASF with inhibited E2F2 expression, and the CCR4 expression was increased in RASF with transfection of E2F2-expressing plasmids. Silencing E2F2 expression stimulated apoptosis, but retarded migration and tube-like structure formation in RASF. The opposite observation was obtained in RASF with E2F2 overexpression.

Conclusions

High E2F2 expression decreases apoptosis and increases migration and tube-like structure ability in RASF and might perform this role by up-regulating CCR4 expression, which ultimately contributes to the disease progression of RA synovial tissues.

CC Chemokines in a Tumor: A Review of Pro-Cancer and Anti-Cancer Properties of the Ligands of Receptors CCR1, CCR2, CCR3, and CCR4

CC chemokines, a subfamily of 27 chemotactic cytokines, are a component of intercellular communication, which is crucial for the functioning of the tumor microenvironment. Although many individual chemokines have been well researched, there has been no comprehensive review presenting the role of all known human CC chemokines in the hallmarks of cancer, and this paper aims at filling this gap. The first part of this review discusses the importance of CCL1, CCL3, CCL4, CCL5, CCL18, CCL19, CCL20, CCL21, CCL25, CCL27, and CCL28 in cancer. Here, we discuss the significance of CCL2 (MCP-1), CCL7, CCL8, CCL11, CCL13, CCL14, CCL15, CCL16, CCL17, CCL22, CCL23, CCL24, and CCL26. The presentation of each chemokine includes its physiological function and then the role in tumor, including proliferation, drug resistance, migration, invasion, and organ-specific metastasis of tumor cells, as well as the effects on angiogenesis and lymphangiogenesis. We also discuss the effects of each CC chemokine on the recruitment of cancer-associated cells to the tumor niche (eosinophils, myeloid-derived suppressor cells (MDSC), tumor-associated macrophages (TAM), tumor-associated neutrophils (TAN), regulatory T cells (T_reg)). On the other hand, we also present the anti-cancer properties of CC chemokines, consisting in the recruitment of tumor-infiltrating lymphocytes (TIL).

Specialized immune responses in the peritoneal cavity and omentum

The peritoneal cavity is a fluid filled space that holds most of the abdominal organs, including the omentum, a visceral adipose tissue that contains milky spots or clusters of leukocytes that are organized similar to those in conventional lymphoid tissues. A unique assortment of leukocytes patrol the peritoneal cavity and migrate in and out of the milky spots, where they encounter Ags or pathogens from the peritoneal fluid and respond accordingly. The principal role of leukocytes in the peritoneal cavity is to preserve tissue homeostasis and secure tissue repair. However, when peritoneal homeostasis is disturbed by inflammation, infection, obesity, or tumor metastasis, specialized fibroblastic stromal cells and mesothelial cells in the omentum regulate the recruitment of peritoneal leukocytes and steer their activation in unique ways. In this review, the types of cells that reside in the peritoneal cavity, the role of the omentum in their maintenance and activation, and how these processes function in response to pathogens and malignancy will be discussed.

Omental adipocytes promote peritoneal metastasis of gastric cancer through the CXCL2-VEGFA axis

Background

Gastric cancer (GC) patients frequently develop peritoneal metastasis; however, the underlying mechanism remains unknown. We hypothesised that omental adipocytes (OmAd) trigger GC cells towards malignant activity to induce peritoneal metastasis.

Methods

We analysed interactions among human GC cells, endothelial cells and OmAd using a 3D co-culture system. We also employed a multipronged animal study, including subcutaneous and orthotopic tumours, and humanised omental adipose tissue models. Urinary levels of CXCL2 were analysed in human GC patients with and without peritoneal metastasis.

Results

Conditioned media derived from OmAd (OmAd-CM) promoted the proliferation, migration and capacity to induce angiogenesis of GC cells through AKT phosphorylation and VEGFA overexpression, whereas silencing CXCL2 in OmAd cancelled OmAd-induced effects. In an orthotopic tumour model using SCID mice, omentectomy suppressed GC growth and peritoneal dissemination, and reduced serum levels of CXCL2. OmAd promoted GC growth in a humanised omental adipose tissue model using NSG mice, but silencing CXCL2 in OmAd cancelled OmAd-induced tumour growth. Finally, urinary levels of CXCL2 were significantly higher in GC patients with peritoneal metastasis than in those without.

Conclusion

Omental adipocytes trigger GC cells to an aggressive phenotype through CXCL2 secretion, which induces angiogenesis followed by cell growth and peritoneal metastasis.

Foliate Lymphoid Aggregates as Novel Forms of Serous Lymphocyte Entry Sites of Peritoneal B Cells and High-Grade B Cell Lymphomas

The cellular homeostasis of lymphoid tissues is determined by the continuous interactions of mobile hematopoietic cells within specialized microenvironments created by sessile stromal cells. In contrast to the lymph nodes and mucosal lymphoid tissues with well-defined entry and exit routes, the movement of leukocytes in the peritoneal cavity is largely unknown. In this study, we report that, in addition to the omental milky spots and fat-associated lymphoid clusters, in mice, the serous surface of the mesenteric adipose streaks contains lymphocyte-rich organoids comprised of a highly compacted leaf-like part connected to the adipose tissue that can also efficiently bind B cells and high-grade B cell lymphoma (diffuse large B cell lymphoma) cells. Denoted as foliate lymphoid aggregates (FLAgs), these structures show incomplete T/B segregation and a partially differentiated stromal architecture. LYVE-1-positive macrophages covering FLAgs efficiently bind i.p. injected normal B cells as well as different types of diffuse large B cell lymphoma cells. Within FLAgs, the lymphocytes compartmentalize according to their chemokine receptor pattern and subsequently migrate toward the mesenteric lymph nodes via the mesenteric lymphatic capillaries. The blood supply of FLAgs includes short vascular segments displaying peripheral lymph node addressin, and the extravasation of lymphocytes to the omental and mesenteric adipose tissues is partly mediated by L-selectin. The appearance of i.p. injected cells in mesenteric lymph nodes suggests that the mesentery-associated lymphatics may also collect leukocytes from the fat-associated lymphoid clusters and FLAgs, thus combining the mucosal and serous exit of mobile leukocytes and increasing the range of drainage sites for the peritoneal expansion of lymphoid malignancies.

Omental Tissue-Mediated Tumorigenesis of Gastric Cancer Peritoneal Metastases

The peritoneal cavity, especially the omentum, is a common site for gastric cancer metastasis, representing advanced disease stage and poor prognosis. Here, we studied the effects of omental tissue on gastric cancer tumor progression in vitro and in vivo. Utilizing in vitro models, we found that omental tissue secreted factors increased gastric cancer cellular growth (by 30–67%, P < 0.05), motility (>8-fold, P < 0.05), invasiveness (>7-fold, P < 0.05) and chemoresistance to platinum-based chemotherapeutic agents (>1.2-fold for oxaliplatin and >1.6-fold for cisplatin, P < 0.05). Using a robust proteomic approach, we identified numerous molecules secreted into the omental tissue conditioned medium (CM) which may promote gastric cancer cellular aggressiveness (i.e., IL-6, IL-8, MMP9, FN1, and CXCL-5). Next, an in vivo xenograft mouse model showed an increased human gastric adenocarcinoma tumor volume of cells co-cultured with human omental tissue secreted factors; 1.6 ± 0.55 vs. 0.3 ± 0.19 cm³ (P < 0.001), as well as increased angiogenesis. Finally, exosomes were isolated from human omental tissue CM of gastric cancer patients. These exosomes were taken up by gastric cancer cells enhancing their growth (>8-fold, P < 0.01) and invasiveness (>8-fold, P < 0.001). Proteomic analysis of the content of these exosomes identified several established cancer- related proteins (i.e., IL-6, IL-8, ICAM-1, CCl2, and OSM). Taken together, our findings imply that the omentum play an active role in gastric cancer metastasis. The data also describe specific cytokines that are involved in this cross talk, and that omental tissue- derived exosomes may contribute to these unique cellular interactions with gastric cancer cells. Further studies aimed at understanding the biology of gastric cancer intra peritoneal spread are warranted. Hopefully, such data will enable to develop future novel therapeutic strategies for the treatment of metastatic gastric cancer.

M2 macrophages confer resistance to 5-fluorouracil in colorectal cancer through the activation of CCL22/PI3K/AKT signaling

Background: M2 macrophages are crucial components of tumor microenvironment that frequently associated with the resistance of therapeutic treatments in human cancers, but their role in the chemosensitivity of colorectal cancer (CRC) to 5-fluorouracil (5-FU) is still obscure. Methods: In our study, we clarified the biological functions of M2 macrophages and their mechanism on the chemosensitivity of CRC cells to 5-FU. Then, we analyzed the correlation between CCL22 and CD68+ and CD163+ tumor-associated macrophages (TAMs), and further elucidated the prognostic value of CCL22 and CD163+ M2 macrophages in clinical CRC samples. Results: M2 macrophages decreased the inhibitory effect of 5-FU on CRC cells migration and invasion by secreting CCL22, and declined the apoptosis induced by 5-FU. Treated with a neutralizing anti-CCL22 antibody destroyed these effects. We further illuminated that M2 macrophages regulated 5-FU resistance of CRC cells through epithelial-mesenchymal transition (EMT) program, PI3K/AKT pathway, and caspase-mediated apoptosis. Clinically, CCL22 was found to have elevated expression in CRC tissue samples, and was positively associated with CD163+ TAMs. Furthermore, the patients with higher CD163+ M2 macrophages and higher expression of CCL22 in CRC tissues had a lower overall survival (OS) rate compared with lower ones. Conclusion: Our findings indicate that M2 macrophage regulated 5-FU-mediated CRC chemoresistance via the EMT program, PI3K/AKT pathway, and caspase-mediated apoptosis by releasing CCL22.

Pressurized intraperitoneal aerosol chemotherapy and its effect on gastric-cancer-derived peritoneal metastases: an overview

This manuscript aspires to portray a review of the current literature focusing on manifest peritoneal metastasis (PM) derived from gastric cancer and its treatment options. Despite the development of chemotherapy and multimodal treatment options during the last decades, mortality remains high worldwide. After refreshing important epidemiological considerations, the molecular mechanisms currently accepted through which PM occurs are revised. Palliative chemotherapy is the only recommended treatment option for patients with PM of gastric cancer according to the National Comprehensive Cancer Network guidelines, although cytoreductive surgery in combination with hyperthermic intraperitoneal chemotherapy demonstrated promising results in selected patients with regional PM and localized intraabdominal tumor spread. A novel treatment named pressurized intraperitoneal aerosol chemotherapy may have a promising future in improving overall survival with an acceptable postoperative complication rate and stabilizing quality of life during treatment. Additionally, the procedure has been proved to be safe for the patient and medical personnel and a feasible, repeatable method to deter metastatic proliferation. This overview comprehensively addresses this novel and promising treatment in the context of a scientifically and clinically challenging disease.

Adipocytes fuel gastric cancer omental metastasis via PITPNC1-mediated fatty acid metabolic reprogramming

Omental metastasis occurs frequently in gastric cancer (GC) and is considered one of the major causes of gastric cancer-related mortality. Recent research indicated that omental adipocytes might mediate this metastatic predilection. Phosphatidylinositol transfer protein, cytoplasmic 1 (PITPNC1) was identified to have a crucial role in metastasis. However, whether PITPNC1 participates in the interaction between adipocytes and GC omental metastasis is unclear. Methods: We profiled and analyzed the expression of PITPNC1 through analysis of the TCGA database as well as immunohistochemistry staining using matched GC tissues, adjacent normal gastric mucosa tissues (ANTs), and omental metastatic tissues. The regulation of PITPNC1 by adipocytes was explored by co-culture systems. By using both PITPNC1 overexpression and silencing methods, the role of PITPNC1 in anoikis resistance and metastasis was determined through in vitro and in vivo experiments. Results: PITPNC1 was expressed at higher rates in GC tissues than in ANTs; notably, it was higher in omental metastatic lesions. Elevated expression of PITPNC1 predicted higher rates of omental metastasis and a poor prognosis. PITPNC1 promoted anoikis resistance through fatty acid metabolism by upregulating CD36 and CPT1B expression. Further, PITPNC1 was elevated by adipocytes and facilitated GC omental metastasis. Lastly, in vivo studies showed that PITPNC1 was a therapeutic indicator of fatty acid oxidation (FAO) inhibition. Conclusion: Elevated expression of PITPNC1 in GC is correlated with an advanced clinical stage and a poor prognosis. PITPNC1 promotes anoikis resistance through enhanced FAO, which is regulated by omental adipocytes and consequently facilitates GC omental metastasis. Targeting PITPNC1 might present a promising strategy to treat omental metastasis.

CCR4 Expression Is Associated With Poor Prognosis in Patients With Early Stage (pN0) Oral Tongue Cancer

PURPOSE

Chemokine receptors are involved in tumor metastasis and can predict poor prognosis; however, the expression and clinicopathologic relevance of chemokine receptors in early-stage cancer remain largely unknown. This study measured the association between chemokine (C-C motif) receptor-4 (CCR4) expression and prognosis in patients with histologically node-negative (pN0) oral tongue cancer.

MATERIALS AND METHODS

A retrospective analysis of CCR4 expression data from a consecutive case series of patients with pN0 oral cancer tongue was conducted. The expression of CCR4 by immunohistochemistry was investigated and the association between CCR4 expression and clinicopathologic variables and overall and disease-free survivals was evaluated using Kaplan-Meier analysis and a Cox regression model.

RESULTS

CCR4 expression was examined in 128 human tongue cancerous samples (109 tongue squamous cell carcinomas [TSCCs] and 19 other types) and 10 normal tongue samples and was found to be highly expressed in tumor tissues compared with normal tissues. CCR4 expression was observed in 64.2% of patients with TSCC and showed a significant association with tumor stage (P = .037). Patients with CCR4-positive expression exhibited poorer overall and disease-free survivals compared with those with CCR4-negative expression (P < .001 and P = .001), and CCR4-positive expression was an independent factor of unfavorable overall and disease-free survivals (P = .002 and P = .007).

CONCLUSIONS

This study identified CCR4 as a potential prognostic biomarker for recurrence and survival of patients with pN0 oral tongue cancer. Thus, CCR4 might be a possible therapeutic target for patients with early-stage cancer.

The T-win® technology: immune-modulating vaccines

The T-win® technology is an innovative investigational approach designed to activate the body's endogenous anti-regulatory T cells (anti-Tregs) to target regulatory as well as malignant cells. Anti-Tregs are naturally occurring T cells that can directly react against regulatory immune cells because they recognize proteins that these targets express, including indoleamine 2,3-dioxygenase (IDO), tryptophan 2,6-dioxygenase, arginase, and programmed death ligand 1 (PD-L1). The T-win® technology is characterized by therapeutic vaccination with long peptide epitopes derived from these antigens and therefore offers a novel way to target genetically stable cells with regular human leukocyte antigen expression in the tumor microenvironment. The T-win® technology thus also represents a novel way to attract pro-inflammatory cells to the tumor microenvironment where they can directly affect immune inhibitory pathways, potentially altering tolerance to tumor antigens. The modification of an immune regulatory environment into a pro-inflammatory milieu potentiates effective anti-tumor T cell responses. Many regulatory immune cells may be reverted into effector cells given the right stimulus. Because T-win® technology is based on the immune-modulatory function of the vaccines, the vaccines activate both CD4 and CD8 anti-Tregs. Of importance, in clinical trials, vaccinations against IDO or PD-L1 to potentiate anti-Tregs have so far proved to be safe, with minimal toxicity.

C-C motif chemokine 22 predicts postoperative prognosis and adjuvant chemotherapeutic benefits in patients with stage II/III gastric cancer

Immune molecules, which have been found to be important in tumor microenvironment, seem prospective in tumor therapy, but they are still not effective enough to use in clinical practice. C-C motif chemokine 22 (CCL22) exists in various malignancies and correlates with migration of regulatory T cells, but its clinical significance in gastric cancer is still unclear. In this study, a combined data set of 466 patients with gastric cancer after surgical resection, comprised of a discovery (n = 319) and a validation data set (n = 147), was enrolled. CCL22 expression was assessed by immunohistochemical staining and we evaluated prognostic values of CCL22 staining and clinical outcomes with use of Kaplan-Meier curve and Multivariate Cox regression analysis. Positive CCL22 expression predicted adverse overall survival independent of traditional pathological grade. Multivariate analysis defined CCL22 and TNM stage as two independent prognostic factors for overall survival. Besides, in patients with TNM stage II/III disease, the rate of overall survival was higher among patients with CCL22-positive tumors who were treated with 5-fluorouracil based adjuvant chemotherapy than that among those who were not (P = 0.012, P < 0.001 and P < 0.001, in discovery, validation and combined data set). But for these with CCL22-negative tumors, whether to undergo adjuvant chemotherapy showed no statistical significance (P = 0.595, P = 0.085 and P = 0.252, respectively). To conclude, CCL22 was identified as an independent adverse prognostic immunobiomarker for patients with gastric cancer after surgery, which is associated with tumor-infiltrating immunocytes and could be incorporated into TNM staging system to redefine a high-risk subgroup who were more likely to benefit from 5-fluorouracil based adjuvant chemotherapy.

Elementary screening of lymph node metastatic-related genes in gastric cancer based on the co-expression network of messenger RNA, microRNA and long non-coding RNA

Gastric cancer (GC) is the fifth most common cancer and the third leading cause of cancer-related deaths worldwide. The high mortality might be attributed to delay in detection and is closely related to lymph node metastasis. Therefore, it is of great importance to explore the mechanism of lymph node metastasis and find strategies to block GC metastasis. Messenger RNA (mRNA), microRNA (miRNA) and long non-coding RNA (lncRNA) expression data and clinical data were downloaded from The Cancer Genome Atlas (TCGA) database. A total of 908 differentially expressed factors with variance >0.5 including 542 genes, 42 miRNA, and 324 lncRNA were screened using significant analysis microarray algorithm, and interaction networks were constructed using these differentially expressed factors. Furthermore, we conducted functional modules analysis in the network, and found that yellow and turquoise modules could separate samples efficiently. The groups classified in the yellow and turquoise modules had a significant difference in survival time, which was verified in another independent GC mRNA dataset (GSE62254). The results suggested that differentially expressed factors in the yellow and turquoise modules may participate in lymph node metastasis of GC and could be applied as potential biomarkers or therapeutic targets for GC.

Correction of T cell deficiency in ZAP-70 knock-out mice by simple intraperitoneal adoptive transfer of thymocytes

The tyrosine kinase zeta chain-associated protein of 70 kDa (ZAP-70) plays a key role in T cell development and signalling. In the absence of ZAP-70, T cell development is arrested in the CD4⁺ CD8⁺ double-positive stage, thus ZAP-70 homozygous knockout (ZAP-70^-/- ) mice have no mature T cells in their peripheral lymphoid organs and blood, causing severe immunodeficiency. We investigated the early kinetics and long-term effects of wild-type thymocyte transfer on T cell repopulation in ZAP-70^-/- mice. We used a single intraperitoneal (i.p.) injection to deliver donor thymocytes to the recipients. Here, we show that after i.p. injection donor thymocytes leave the peritoneum through milky spots in the omentum and home to the thymus, where donor-originated CD4^- CD8^- double-negative thymocytes most probably restore T cell development and the disrupted thymic architecture. Subsequently, newly developed, donor-originated, single-positive αβ T cells appear in peripheral lymphoid organs, where they form organized T cell zones. The established chimerism was found to be stable, as donor-originated cells were present in transferred ZAP-70^-/- mice as late as 8 months after i.p. injection. We demonstrate that a simple i.p. injection of ZAP-70^+/+ thymocytes is a feasible method for the long-term reconstitution of T cell development in ZAP-70-deficient mice.

Mechanisms of peritoneal dissemination in gastric cancer

Peritoneal dissemination is the most frequent metastatic pattern of gastric cancer, but the mechanisms underlying peritoneal dissemination are yet to be elucidated. Paget's 'seed and soil' hypothesis is recognized as the fundamental theory of metastasis. The 'seeding' theory proposes that the formation of peritoneal dissemination is a multistep process, including detachment from the primary tumour, transmigration and attachment to the distant peritoneum, invasion into subperitoneal tissue and proliferation with blood vascular neogenesis. In the present review, the progress of each step is discussed. Milky spots, as a lymphatic apparatus, are indicative of lymphatic orifices on the surface of the peritoneum. These stomata are open gates for peritoneal-free cancer cells to migrate into the submesothelial space. Therefore, milky spots provide suitable 'soil' for cancer cells to implant. Other theories have also been proposed to clarify the peritoneal dissemination process, including the transvessel metastasis theory, which suggests that the peritoneal metastasis of gastric cancer develops via a vascular network mediated by hypoxia inducible factor-1α.

Immunological Functions of the Omentum

The omentum is a visceral adipose tissue with unique immune functions. Although it is primarily an adipose tissue, the omentum also contains lymphoid aggregates, called milky spots (MSs), that contribute to peritoneal immunity by collecting antigens, particulates, and pathogens from the peritoneal cavity and, depending on the stimuli, promoting a variety of immune responses, including inflammation, tolerance, or even fibrosis. Reciprocal interactions between cells in the MS and adipocytes regulate their immune and metabolic functions. Importantly, the omentum collects metastasizing tumor cells and supports tumor growth by immunological and metabolic mechanisms. Here we summarize our current knowledge about the development, organization, and function of the omentum in peritoneal immunity.

Role of LAP+CD4+ T cells in the tumor microenvironment of colorectal cancer

AIM

To investigate the abundance and potential functions of LAP⁺CD4⁺ T cells in colorectal cancer (CRC).

METHODS

Proportions of LAP⁺CD4⁺ T cells were examined in peripheral blood and tumor/paratumor tissues of CRC patients and healthy controls using flow cytometry. Expression of phenotypic markers such as forkhead box (Fox)p3, cytotoxic T-lymphocyte-associated protein (CTLA)-4, chemokine CC receptor (CCR)4 and CCR5 was measured using flow cytometry. LAP^-CD4⁺ and LAP⁺CD4⁺ T cells were isolated using a magnetic cell-sorting system and cell purity was analyzed by flow cytometry. Real-time quantitative polymerase chain reaction was used to measure expression of cytokines interleukin (IL)-10 and transforming growth factor (TGF)-β.

RESULTS

The proportion of LAP⁺CD4⁺ T cells was significantly higher in peripheral blood from patients (9.44% ± 3.18%) than healthy controls (1.49% ± 1.00%, P < 0.001). Among patients, the proportion of LAP⁺CD4⁺ T cells was significantly higher in tumor tissues (11.76% ± 3.74%) compared with paratumor tissues (3.87% ± 1.64%, P < 0.001). We also observed positive correlations between the proportion of LAP⁺CD4⁺ T cells and TNM stage (P < 0.001), distant metastasis (P < 0.001) and serum level of carcinoembryonic antigen (P < 0.05). Magnetic-activated cell sorting gave an overall enrichment of LAP⁺CD4⁺ T cells (95.02% ± 2.87%), which was similar for LAP^-CD4⁺ T cells (94.75% ± 2.76%). In contrast to LAP^-CD4⁺ T cells, LAP⁺CD4⁺ T cells showed lower Foxp3 expression but significantly higher levels of CTLA-4, CCR4 and CCR5 (P < 0.01). LAP⁺CD4⁺ T cells expressed significantly larger amounts of IL-10 and TGF-β but lower levels of IL-2, IL-4, IL-17 and interferon-γ, compared with LAP^-CD4⁺ T cells.

CONCLUSION

LAP⁺CD4⁺ T cells accumulated in the tumor microenvironment of CRC patients and were involved in immune evasion mediated by IL-10 and TGF-β.

Fucoidan inhibits CCL22 production through NF-κB pathway in M2 macrophages: a potential therapeutic strategy for cancer

In tumor microenvironment, macrophages as a polarized M2 population promote tumor progression via releasing multiple cytokines and chemokines. A brown seaweed fucose-rich polysaccharide, fucoidan has antitumor activity and immune modulation through affecting tumor cells and lymphocytes. Here, we focused on the effect of fucoidan on macrophages especially M2 subtype. Our results demonstrated that fucoidan down-regulated partial cytokines and chemokines, especially a M2-type chemokine CCL22. Furthermore, fucoidan inhibited tumor cells migration and CD4⁺ T lymphocytes, especially Treg cells, recruitment induced by M2 macrophages conditioned medium through suppression of CCL22. Mechanismly, fucoidan inhibited CCL22 via suppressing p65-NF-κB phosphorylation and nuclear translocation. In addition, p38-MAPK and PI3K-AKT also affected the expression of CCL22 through differential modulation of NF-κB transcriptional activity. Taken together, we reveal an interesting result that fucoidan can inhibit tumor cell migration and lymphocytes recruitment by suppressing CCL22 in M2 macrophages via NF-κB-dependent transcription, which may be a novel and promising mechanism for tumor immunotherapy.

CCL22-specific T Cells: Modulating the immunosuppressive tumor microenvironment

Tumor cells and tumor-infiltrating macrophages produce the chemokine CCL22, which attracts regulatory T cells (Tregs) into the tumor microenvironment, decreasing anticancer immunity. Here, we investigated the possibility of targeting CCL22-expressing cells by activating specific T cells. We analyzed the CCL22 protein signal sequence, identifying a human leukocyte antigen A2- (HLA-A2-) restricted peptide epitope, which we then used to stimulate peripheral blood mononuclear cells (PMBCs) to expand populations of CCL22-specific T cells in vitro. T cells recognizing an epitope derived from the signal-peptide of CCL22 will recognize CCL22-expressing cells even though CCL22 is secreted out of the cell. CCL22-specific T cells recognized and killed CCL22-expressing cancer cells. Furthermore, CCL22-specific T cells lysed acute monocytic leukemia cells in a CCL22 expression-dependent manner. Using the Enzyme-Linked ImmunoSPOT assay, we examined peripheral blood mononuclear cells from HLA-A2+ cancer patients and healthy volunteers for reactivity against the CCL22-derived T-cell epitope. This revealed spontaneous T-cell responses against the CCL22-derived epitope in cancer patients and in healthy donors. Finally, we performed tetramer enrichment/depletion experiments to examine the impact of HLA-A2-restricted CCL22-specific T cells on CCL22 levels among PMBCs. The addition or activation of CCL22-specific T cells decreased the CCL22 level in the microenvironment. Activating CCL22-specific T cells (e.g., by vaccination) may directly target cancer cells and tumor-associated macrophages, thereby modulating Treg recruitment into the tumor environment and augmenting anticancer immunity.

Anti-regulatory T cells

Our initial understanding of immune-regulatory cells was based on the discovery of suppressor cells that assure peripheral T-cell tolerance and promote immune homeostasis. Research has particularly focused on the importance of regulatory T cells (Tregs) for immune modulation, e.g. directing host responses to tumours or inhibiting autoimmunity development. However, recent studies report the discovery of self-reactive pro-inflammatory T cells-termed anti-regulatory T cells (anti-Tregs)-that target immune-suppressive cells. Thus, regulatory cells can now be defined as both cells that suppress immune reactions as well as effector cells that counteract the effects of suppressor cells and support immune reactions. Self-reactive anti-Tregs have been described that specifically recognize human leukocyte antigen-restricted epitopes derived from proteins that are normally expressed by regulatory immune cells, including indoleamine 2,3-dioxygenase (IDO), tryptophan 2,6-dioxygenase (TDO), programmed death-ligand 1 (PD-L1), and forkhead box P3 (Foxp3). These proteins are highly expressed in professional antigen-presenting cells under various physiological conditions, such as inflammation and stress. Therefore, self-reactive T cells that recognize such targets may be activated due to the strong activation signal given by their cognate targets. The current review describes the existing knowledge regarding these self-reactive anti-Tregs, providing examples of antigen-specific anti-Tregs and discussing their possible roles in immune homeostasis and their potential future clinical applications.

Greater Omental Milky Spot Examination for Diagnosis of Peritoneal Metastasis in Gastric Cancer Patients

OBJECTIVE

To evaluate the diagnostic value of cytological greater omental milky spot examination for the diagnosis of peritoneal metastasis in gastric cancer patients.

METHODS

A total of 136 patients diagnosed with gastric cancer and without distant metastasis were enrolled in our study. All patients underwent laparoscopy and CH40 suspension liquid dye of peritoneal lymph nodes preoperatively as well as ascites or peritoneal lavage fluid collections and excisions of marked greater omental milky spot tissues perioperatively.

RESULTS

According to the laparoscopic results, the patients were divided into T1-T2 stage (n = 56) without and into T3-T4 stage (n = 80) with tumor invasion into the serosal layer. Among the T1-T2-stage patients, tumor cells could be detected in peritoneal lavage fluids in 2 cases, whereas with greater omental milky spot examination, peritoneal metastasis was detected in 8 cases. Among the 80 cases in the T3-T4 stage, tumor cells could be detected in 28 cases via peritoneal lavage cytology and in 43 cases by greater omental milky spot examinations, and 4 cases had cancer cell infiltration also in nonmilky spot omental areas. The statistical analysis showed that the staging accuracy rate of exfoliative cytology examination was superior to that of the laparoscopic exploration (P < .05), but its sensitivity was significantly lower than that obtained with cytological greater omental milky spot examinations (P < .05).

CONCLUSIONS

The laparoscopic exploration could make a preliminary diagnosis of peritoneal metastasis via serosal layer invasion detection. For further analyses, cytological examinations of greater omental milky spots were more sensitive than exfoliative cytology.

Effect of tumor-associated macrophages on gastric cancer stem cell in omental milky spots and lymph node micrometastasis

We observed whether the effect of tumor-associated macrophages on gastric cancer stem cell in omental milky spots and lymph nodes micrometastasis and research its possible mechanism. Macrophage THP-1 cells and Human gastric adenocarcinoma SGC-7901 cells were collectively cultivated in vivo. We found macrophage could suppress the proliferation and accelerated cell death of MFC cell. Meanwhile, these effects may be concerned with many signaling pathways, and we detected MCP-1 and COX-2 miRNA expressions, PGE-2 release levels, IL-4 and IL-10 activities, and TGF-β, IFN-γ, VEGF, MMP-2 and MMP-9 protein expressions in collectively cultivated cell. We found that MCP-1 and COX-2 miRNA expressions, and PGE-2 release levels were suppressed, IL-4 activity was inhibited and IL-10 activity was activated in collectively cultivated cell. Meanwhile, TGF-β, MMP-2 and MMP-9 protein expressions were inhibited and IFN-γ and VEGF protein expressions were activated in collectively cultivated cell. Taken together, these results suggest that the effect of tumor-associated macrophages on gastric cancer stem cell in omental milky spots and lymph nodes micrometastasis via COX-2/PGE-2/TGF-β/VEGF signal pathways.