Role of the tumor microenvironment in the pathogenesis of gastric carcinoma

Association of mast cell infiltration with gastric cancer progression

The present study aimed to determine the expression of mast cells, C-C motif chemokine ligand 2 (CCL-2) and C-C motif chemokine receptor 2 (CCR2) in gastric cancer tumor tissue; and the association of mast cells with the proliferation, migration, invasion and apoptosis of gastric cancer cells. In addition, whether the stem cell factor (SCF)/c-Kit pathway was associated with the secretion of CCL-2 by gastric cancer cells was explored. Flow cytometry analysis and immunohistochemistry were used to observe the relative number of mast cells, and reverse transcription-quantitative polymerase chain reaction and western blot analysis were utilized to determine the expression of CCL-2 and CCR2 mRNA and protein. Following the co-culture of the mast cell line HMC-1 and the gastric cancer cell line BGC-823, a Transwell assay was used to validate the effect of mast cells on the migration and invasion of gastric cancer cells. Furthermore, Cell Counting kit-8 and dual acridine orange/ethidium bromide fluorescent staining assays were performed to determine the proliferation and apoptosis of gastric cancer cells, following co-culture with mast cells. The expression of SCF and c-Kit were also determined with a western blot analysis. A specific phosphoinositide 3-kinase (PI3K) inhibitor, wortmannin, was used to test the effect of PI3K inhibition on the secretion of CCL-2 in gastric cancer. The results demonstrated that the proportion of infiltrating mast cells, and the mRNA/protein expression of CCL-2 and CCR2, were significantly increased in tumor tissue relative to adjacent tissues. In addition, the migration and invasion of gastric cancer cells were significantly increased when mast cells were used as an attractant. When co-cultured with mast cells, the viability of gastric cancer cells was significantly increased and H₂O₂-induced apoptosis was inhibited. In gastric cancer tissue samples, the expression of SCF, c-Kit and phosphorylated (p)-Akt protein were significantly increased compared with normal adjacent tissues. It was hypothesized that SCF/c-Kit signaling pathway was activated by PI3K-Akt, resulting in an increase in the expression of CCL-2 mRNA and protein. Furthermore, it was demonstrated that CCL-2 mRNA and protein expression was significantly inhibited by treatment with the PI3K inhibitor wortmannin. Additionally, wortmannin intervention significantly inhibited gastric cancer cell migration and invasion. Therefore, the results of the present study demonstrated that mast cells may promote gastric cancer cell proliferation, migration and invasion, and inhibit apoptosis. In addition, the activation of the SCF/c-Kit signaling pathway was identified to promote the expression of CCL-2, which is associated with the development and metastasis of gastric cancer.

Complement C5a/C5aR pathway potentiates the pathogenesis of gastric cancer by down-regulating p21 expression

Although the complement C5a/C5aR pathway is suggested to play a critical role in tumor pathogenesis, the underlying mechanism has yet to be fully elucidated. In the present study, we found that in patients with gastric cancer in different clinical stages (from stageⅠto stage Ⅳ), both C5aR and p-PI3K/AKT levels were significantly higher in tumoral tissues than in adjacent non-tumoral tissues. In contrast, p21/p-p21 levels were significantly lower in tumoral tissues than in adjacent non-tumoral tissues. In vitro recombinant C5a administration remarkably promoted p-PI3K/p-AKT expression, but inhibited p21/p-p21 expression. Blockage of C5a/C5aR signaling with a C5aR antagonist reversed the C5a-induced inhibitory effect on p21/p-p21 expression. C5a administration to cells pre-treated with a PI3K inhibitor also prevented this inhibitory effect, suggesting the involvement of the PI3K/AKT signaling pathway in C5a/C5aR-mediated suppression of p21/p-p21 expression. In vivo C5aR antagonist treatment caused significant reduction in tumor growth in mice, accompanied by a remarkable elevation in p21/p-p21 expression and reduction in p-PI3K/AKT activation. These results indicate that the C5a/C5aR pathway promotes gastric cancer pathogenesis by suppressing p21/p-p21 expression via activation of PI3K/AKT signaling.

Tumor-stroma ratio (TSR) in non-small cell lung cancer (NSCLC) patients after lung resection is a prognostic factor for survival

Background

In recent years, the tumor-stroma ratio (TSR) has been considered to a new and independent predictive variable for the prognosis of some kinds of neoplasms. The objective of this study was to assess the prognostic significance of the TSR in non-small cell lung cancer (NSCLC).

Methods

A cohort of 261 NSCLC patients who underwent radical surgery of lung cancer were included in the present study. Two independent observers visually estimated the TSR on hematoxylin-eosin (H&E) stained tissue pathological slices. According to the proportion of stroma ≥50% or <50%, We separate the patients into two groups: those with stroma-poor and those with stroma-rich tumors.

Results

Both univariate and multivariate analyses disclosed that the TSR was associated with overall survival (OS) [hazard ratio (HR), 1.741; 95% confidence intervals (CI), 1.040-2.913 and HR, 1.904; 95% CI, 1.132-3.202, respectively]. The HR values for disease-free survival (DFS) were 1.795 (95% CI, 1.073-3.005) and 2.034 (95% CI, 1.210-3.420). The OS and DFS of patients with stroma-poor tumors were better than those with stroma-rich tumors.

Conclusions

These results demonstrated that the TSR is a new prognostic factor for NSCLC. Stroma-poor tumors were associated with longer disease-free period and better prognosis than were stroma-rich tumors in NSCLC patients. The TSR may contribute to the development of individualized treatment for NSCLC in the future.

From inflammation to gastric cancer - the importance of Hedgehog/GLI signaling in Helicobacter pylori-induced chronic inflammatory and neoplastic diseases

Infections with the human pathogen Helicobacter pylori (H. pylori) are closely associated with the development of inflammatory disorders and neoplastic transformation of the gastric epithelium. Drastic changes in the micromilieu involve a complex network of H. pylori-regulated signal transduction pathways leading to the release of proinflammatory cytokines, gut hormones and a wide range of signaling molecules. Besides controlling embryonic development, the Hedgehog/GLI signaling pathway also plays important roles in epithelial proliferation, differentiation, and regeneration of the gastric physiology, but also in the induction and progression of inflammation and neoplastic transformation in H. pylori infections. Here, we summarize recent findings of H. pylori-associated Hedgehog/GLI signaling in gastric homeostasis, malignant development and the modulation of the gastric tumor microenvironment.

Pretreatment neutrophil-lymphocyte count ratio may associate with gastric cancer presence

BACKGROUND

Inflammation plays a pivotal role in cancer development and progression. Neutrophil-lymphocyte count ratio (NLR) is an indicator of systemic inflammatory response which is supposedly associated with gastric cancer (GC) development and progression. Since this parameter can be easily obtained from routine blood examination, it will be a great economic relief to gastric patients if we can bring it into clinical application.

OBJECTIVE

The current study aims to evaluate the pretreatment NLR in gastric cancer patients through retrospectively reviewing the medical records.

METHODS

A total of 327 patients hospitalized on a tertiary care hospital were retrospectively investigated and divided into two groups. Gastric cancer group were composed of patients with newly diagnosed, pathologically confirmed GC and the control group were patients with gastric polyp or benign gastric stromal tumor. The value of NLR in the presence and stage of gastric cancer was investigated in the entire gastric cancer group.

RESULTS

Our study showed levels of NLR were significantly higher in gastric cancer cohort (2.17 (1.63-3.09) versus 1.62 (0.85-2.32), p< 0.001). After all the known confounders were excluded, NLR was an independent predicator of GC (OR = 1.446, 95%CI (1.121-1.866), and P= 0.005). Area under ROC curve (AUC) of NLR was 0.694. In addition, the results of Spearman's correlation showed NLR may have a positive correlation with size of tumor, N-stage, distant metastasis, and overall stage (r = 0.256, 0.256, 0.161 and 0.171, resp., all p < 0.05).

CONCLUSIONS

The current study demonstrated that pre-treatment NLR may be a useful biomarker in the health care of gastric cancer patients.

Lysyl oxidase isoforms in gastric cancer

Gastric cancer (GC) is the fifth most frequent cancer in the world and shows the highest incidence in Latin America and Asia. An increasing amount of evidence demonstrates that lysyl oxidase isoforms, a group of extracellular matrix crosslinking enzymes, should be considered as potential biomarkers and therapeutic targets in GC. In this review, we focus on the expression levels of lysyl oxidase isoforms, its functions and the clinical implications in GC. Finding novel proteins related to the processing of these extracellular matrix enzymes might be helpful in the design of new therapies, which, in combination with classic pharmacology, could be used to delay the progress of this aggressive cancer and offer a wider temporal window for clinical intervention.

C5b-9 Staining Correlates With Clinical and Tumor Stage in Gastric Adenocarcinoma

The complement system is a critical part of the immune response, acting in defense against viral infections, clearance of immune complexes, and maintenance of tissue homeostasis. Upregulated expression of the terminal complement complex, C5b-9, has been observed on various tumor cells, such as stomach carcinoma cells, and on cells in the necrotic regions of these tumors as well; however, whether and how C5b-9 is related to gastric cancer progression and severity remains unknown. In this study, human gastric adenocarcinoma (HGAC) tissues (n=47 cases) and patient-matched adjacent nontumoral parenchyma (n=20 cases) were evaluated by tissue microarray and immunohistochemistry. The HGAC tissues showed upregulated C5b-9 expression. Multinomial logistic regression and likelihood ratio testing showed that overexpression of C5b-9 in HGAC tissue was significantly correlated with clinical stage (P=0.007) and tumor stage (P=0.005), but not with tumor distant organ metastasis, lymphoid nodal status, sex, or age. Patients with late-stage gastric adenocarcinoma had a higher amount of tumor cells showing positive staining for C5b-9 than patients with early-stage disease. These results may help in diagnosis and assessment of disease severity of human gastric carcinoma.

Diffuse-type gastric cancer cells switch their driver pathways from FGFR2 signaling to SDF1/CXCR4 axis in hypoxic tumor microenvironments

Cancer-associated fibroblasts (CAFs) have been considered to play an important role for tumor progression of cancer. Solid tumors contain heterogeneous distribution of oxygen in their microenvironments. This study investigated the growth signaling of gastric cancer (GC) cells in focus on the interaction with CAFs and GC cells under normoxia and hypoxia. Four diffuse-type GC cell lines, two intestinal-type GC cell lines and three CAF cell lines were used. Cells were examined for expression of C-X-C chemokine receptor 4 (CXCR4), fibroblast growth factor receptor 2 (FGFR2) and stromal-derived factor 1 (SDF1) by RT-PCR, western blot, ELISA and immunohistochemical staining of xenografted tumors. GC cell proliferation was examined under hypoxia in the presence or absence of CAFs, a FGFR2 inhibitor, a CXCR4 inhibitor and HIF1α siRNA. Proliferation of diffuse-type GC cells, but not intestinal-type GC cells, was significantly increased by CAFs. CXCR4 expression by diffuse-type GC cells was significantly increased in hypoxia, while FGFR2 expression was decreased. CXCR4 expression was correlated with hypoxic microenvironment of xenografted tumor, but FGFR2 expression was not. FGFR2 inhibition significantly decreased the growth-stimulating activity of CAFs for diffuse-type GC cells in normoxia. In contrast, CXCR4 inhibition significantly decreased the growth-stimulating activity of CAFs in hypoxia. SDF1 production by CAFs was increased in hypoxia, while cancer cells did not produce SDF1. HIF1 siRNA significantly decreased both CXCR4 expression by diffuse-type GC cells and SDF1 production by CAFs. These findings suggest that diffuse-type GC cells might switch their driver pathways from FGFR2 signaling to SDF1/CXCR4 axis through HIF1 in hypoxic tumor microenvironments.

Immunosuppression associated with chronic inflammation in the tumor microenvironment

Chronic inflammation contributes to cancer development via multiple mechanisms. One potential mechanism is that chronic inflammation can generate an immunosuppressive microenvironment that allows advantages for tumor formation and progression. The immunosuppressive environment in certain chronic inflammatory diseases and solid cancers is characterized by accumulation of proinflammatory mediators, infiltration of immune suppressor cells and activation of immune checkpoint pathways in effector T cells. In this review, we highlight recent advances in our understanding of how immunosuppression contributes to cancer and how proinflammatory mediators induce the immunosuppressive microenvironment via induction of immunosuppressive cells and activation of immune checkpoint pathways.

Role of cancer-associated fibroblasts in invasion and metastasis of gastric cancer

Cancer-associated fibroblasts (CAFs) are important components of various types of tumors, including gastric cancer (GC). During tumorigenesis and progression, CAFs play critical roles in tumor invasion and metastasis via a series of functions including extracellular matrix deposition, angiogenesis, metabolism reprogramming and chemoresistance. However, the mechanism of the interaction between gastric cancer cells and CAFs remains largely unknown. MicroRNAs (miRNAs) are a class of non-coding small RNA molecules, and their expression in CAFs not only regulates the expression of a number of target genes but also plays an essential role in the communication between tumor cells and CAFs. In this review, we provide an overview of recent studies on CAF miRNAs in GC and the relevant signaling pathways in gastrointestinal tumors. Focusing the attention on these signaling pathways may help us better understand their role in tumor invasion and metastasis and identify new molecular targets for therapeutic strategies.

Anti-angiogenesis therapy and gap junction inhibition reduce MDA-MB-231 breast cancer cell invasion and metastasis in vitro and in vivo

Cancer cells secrete VEGF, which plays a key role in their growth, invasion, extravasation and metastasis. Direct cancer cell-endothelial cell interaction, mediated by gap junctions, is of critical importance in the extravasation process. In this study, we evaluated avastin (Av), an anti-VEGF antibody; and oleamide (OL), a gap junction inhibitor, using MDA-MB-231 human breast cancer cells in vitro and a xenograft murine model in vivo. Results showed that Av/OL significantly decreased proliferation, induced cell cycle arrest and decreased migration and invasion of MDA-MB-231 cells in vitro. In addition, Av/OL significantly decreased homo and hetero-cellular communication interaction between MDA-MDA and MDA-endothelial cells, respectively. The expression levels of several factors including VEGF, HIF1α, CXCR4, Cx26, Cx43, and MMP9 were attenuated upon Av/OL treatment in vitro. On the other hand, avastin, but not oleamide, reduced tumor size of NSG mice injected subdermally (s.d.) with MDA-MB-231 cells, which was also associated with increased survival. Furthermore, Av but also OL, separately, significantly increased the survival rate, and reduced pulmonary and hepatic metastatic foci, of intravenously (i.v.) injected mice. Finally, OL reduced MMP9 protein expression levels, better than Av and in comparisons to control, in the lungs of MDA-MB-231 i.v. injected NSG mice. In conclusion, while avastin has anti-angiogenic, anti-tumor and anti-metastatic activities, oleamide has anti-metastatic activity, presumably at the extravasation level, providing further evidence for the role of gap junction intercellular communication (GJIC) in cancer cell extravasation.

Effect and Molecular Mechanisms of Traditional Chinese Medicine on Regulating Tumor Immunosuppressive Microenvironment

Traditional Chinese medicine (TCM) is an important complementary strategy for treating cancer in China. The mechanism is related to regulating the internal environment and remodeling the tumor immunosuppressive microenvironment (TIM). Herein we illustrate how TIM is reformed and its protumor activity on promoting tumor cell proliferation, angiogenesis and lymphangiogenesis, tumor invasion, and the oncogenicity of cancer stem cells. Furthermore we summarize the effects and mechanism of TCM on regulating TIM via enhancing antitumor immune responses (e.g., regulating the expression of MHC molecules and Fas/FasL, attenuating cancerigenic ability of cancer stem cells) and remolding immunosuppressive cells (e.g., reversing immune phenotypes of T lymphocytes and tumor associated macrophages, promoting dendritic cells mature, restraining myeloid derived suppressor cells function, and regulating Th1/Th2 factors). We also reveal the bidirectional and multitargeting functions of TCM on regulating TIM. Hopefully, it provides new theoretical basis for TCM clinical practice in cancer treatment and prevention.

Serum ENA78/CXCL5, SDF-1/CXCL12, and their combinations as potential biomarkers for prediction of the presence and distant metastasis of primary gastric cancer

BACKGROUND

Chemokines play important roles in cancer development and progression. Epithelial-derived neutrophil-activating peptide-78 (ENA78/CXCL5) and stromal cell-derived factor (SDF-1/CXCL12) supposedly contribute to gastric cancer (GC) development and progression. This study aims to evaluate serum levels of ENA78/CXCL5 and SDF-1/CXCL12 along the GC carcinogenesis, and analyze their clinical significance, and diagnostic potentials through human serum samples.

METHODS

A total of 300 subjects were enrolled in this study. Serum levels of ENA78/CXCL5 and SDF-1/CXCL12, measured by chemiluminescent immunoassay, were compared among 4 disease groups; normal, high-risk (intestinal metaplasia and adenoma), early GC (EGC), and advanced GC (AGC) groups in both training (n=25 per group) and validation dataset (n=70, 30, 50, 50, respectively) by ANOVA test (post hoc Bonferroni). Correlations between serum ENA78/CXCL5 or SDF-1/CXCL12 levels and clinicopathological parameters of GC patients were evaluated (Spearman's correlation; γs). To validate the diagnostic accuracy, receiver operating characteristic (ROC) curve and logistic regression analysis was performed.

RESULTS

Serum ENA78/CXCL5 and SDF-1/CXCL12 levels were significantly higher in AGC groups than EGC, high-risk and normal groups in both training and validation dataset (Bonferroni, from p<0.01 to p<0.001). Clinicopathologically, serum ENA78/CXCL5 was correlated with T-stage (γs=0.231, p=0.021) and distant metastasis (γs=0.357, p<0.001), while serum SDF-1/CXCL12 was correlated with lymph node (γs=0.220, p=0.029) and distant (γs=0.425, p<0.001) metastasis. ROC curve and logistic regression demonstrated that serum ENA78/CXCL5 and SDF-1/CXCL12 showed higher diagnostic accuracy compared with carcinoembryonic antigen (CEA) in predicting GC. Serum ENA78/CXCL5 could predict both the presence of GC and distant metastasis, while serum SDF-1/CXCL12 could mainly predict its distant metastasis. All combination of serum ENA78/CXCL5, SDF-1/CXCL12, and CEA achieved 92.8% specificity at 75.0% sensitivity to predict distant metastasis of GC.

CONCLUSIONS

Combinations of initial serum ENA78/CXCL5, SDF-1/CXCL12, and CEA before any treatment for GC can produce valuable serum biomarker panels to predict the presence and distant metastasis of GC.

Notch4 promotes gastric cancer growth through activation of Wnt1/β-catenin signaling

Gastric cancer (GC) is one of the most common cancers and lethal malignancies in the world. Discovering novel biomarkers that correlate with GC may provide opportunities to reduce the severity of GC. As one of Notch receptor family members in mammals, Notch4 plays an important role in carcinogenesis of several tumors. However, the precise function and mechanism of Notch4 in GC remain undefined. To address this question, we investigated whether Notch4 could be involved in GC progression. We found that Notch4 was activated by overexpressing exogenous intracellular domain of Notch4 (ICN4), and Notch4 activation promoted GC growth in vitro and in vivo, while Notch4 inhibition using ICN4 siRNA had opposite effects. In addition, Notch4 activation induced expression and activation of Wnt1, β-catenin and downstream target genes, c-Myc and cyclin D1, in GC cells, while Notch4 inhibition had opposite effects. Moreover, β-catenin depletion by siRNA attenuated cell proliferation induced by Notch4 activation. Therefore, our results revealed that Notch4 activates Wnt1/β-catenin signaling to regulate GC growth.

TGF-β1 influences polarity characteristics of epithelial cells during process of culture of colon tissues from neonatal rats in vitro

AIM: To establish a neonatal rat colon tissue culture system and to analyze the effect of transforming growth factor-β1 (TGF-β1) on polarity characteristics of epithelial cells.

METHODS: Forty-eight hours after 10 ng/mL TGF-β1 was added during the process of culture of colon tissues from neonatal rats, the expression changes of Crumbs3, E-cadherin and alpha smooth muscle actin (α-SMA) in the control group (without TGF-β1) and intervention group (with TGF-β1) were detected by IHC and RT-PCR.

RESULTS: Pavement-like cells could be seen around tissues in the control group after 48 h; Crumbs3 was mainly located at the apical membrane of epithelial cells (P < 0.01); a single layer of α-SMA-positive myofibroblasts along the crypt axis was visible, and α-SMA was lowly expressed in the smooth muscle. However, cells in the intervention group showed different morphology and size; E-cadherin was mainly present in the cytoplasm, and E-cadherin expression was lower than that in the control group (P < 0.05); α-SMA was abundantly expressed in activated fibroblasts (P < 0.01). The mRNA expression of E-cadherin and Crumbs3 in the control group was significantly lower than that in the intervention group (P < 0.05), while the mRNA expression of α-SMA in the intervention group was significantly higher than that in the control group (P < 0.01).

CONCLUSION: TGF-β1 induced down-regulation of Crumbs3 and then dramatically changed the phenotype of epithelial cells.

IL-22 promotes the migration and invasion of gastric cancer cells via IL-22R1/AKT/MMP-9 signaling

IL-22, one important inflammatory cytokine of the IL-10 family, exerts its functions via IL-22 receptor that is composed of IL-22R1 and IL-10R2 subunits. Although IL-22 expression is reported to be elevated in many cancers, and increased IL-22 expression correlates with tumor progression and poor prognosis, little is known about the role of IL-22 in gastric cancer. In our study, we found that IL-22 stimulation promoted the migration and invasion of SGC-7901 cells. Furthermore, IL-22 increased AKT activation and MMP-9 production in a time- and dose-dependent manner, while knockdown of IL-22R1 attenuated the effect of IL-22 on gastric cancer cells. In addition, blocking of AKT activation suppressed the expression and secretion of MMP-9. Taken together, this present study suggests that IL-22 stimulation enhances the migration and invasion of gastric cancer cells by regulating IL-22R1/AKT/MMP-9 signaling axis.