βig-h3 supports gastric cancer cell adhesion, migration and proliferation in peritoneal carcinomatosis

PDCD4 regulates apoptosis in human peritoneal mesothelial cells and promotes gastric cancer peritoneal metastasis

OBJECTIVE

Programmed cell death 4 (PDCD4) is a tumor suppressor gene, however, the function and regulatory mechanism remain to be discovered. The connection between tumorigenesis and apoptosis is one of the most important foci of cancer research. Our study aimed to explore the connections between PDCD4-mediated apoptosis of human peritoneal mesothelial cells (HPMC) and peritoneal metastasis in gastric cancer.

METHODS

The PDCD4 expression in 31 pairs of HPMC and tumor tissues was assessed by immunohistochemistry and RT-PCR. In cell experiments, we monitored gastric cancer cell migration with a Transwell chamber assay when PDCD4 was silenced in HPMC. Subsequently, apoptosis of HPMC was detected by a flow cytometric assay and western blotting. After analyzing cytokines in culture supernatants from gastric cancer with enzyme-linked immunosorbent assays (ELISAs), transforming growth factor-beta 1 (TGF-β1) was abundant in the culture supernatants of gastric cancer. Then, PDCD4 expression in HMrSV5 cells was analyzed by western blotting after retreatment with different concentrations of TGF-β1. Moreover, apoptosis of peritoneal mesothelial cells treated with TGF-β1 was detected according to the above methods.

RESULTS

In human metastatic peritoneal tissues, the expression of PDCD4 was significantly lower than that in normal tissues. At the same time, decreased expression of PDCD4 in HPMC was associated with increased migration capacity of gastric cancer cells. Moreover, suppressing the expression of PDCD4 promoted apoptosis in mesothelial cells which may be regulated by TGF-β secreted from gastric cancer cells.

CONCLUSIONS

These data suggested that decreased expression of PDCD4 significantly promoted apoptosis in human peritoneal mesothelial cells, thus inducing peritoneal metastasis, and that TGF-β1 secreted from gastric cancer cells may have played a crucial role.

Identification of specific modules and hub genes associated with the progression of gastric cancer

Gastric cancer (GC) has high morbidity and mortality rates worldwide. Abundant literature has reported several individual genes and their related pathways intimately involved in tumor progression. However, little is known about GC progression at the gene network level. Therefore, understanding the underlying mechanisms of pathological transition from early stage to late stage is urgently needed. This study aims to identify potential vital genes and modules involved in the progression of GC. To understand the gene regulatory network of GC progression, we analyzed micro RNAs and messenger RNA s expression profiles by using a couple of bioinformatics tools. miR-205 was identified by differentially expressed analysis and was further confirmed through using multiple kernel learning-based Kronecker regularized least squares. Using weighted gene co-expression network analysis, the gastric cancer progression-related module, which has the highest correlation value with cancer progression, was obtained. Kyoto Encyclopedia of Genes and Genomes pathways and biological processes of the GCPR module genes were related to cell adhesion. Meanwhile, large-scale genes of GCPR module were found to be targeted by miR-205, including two hub genes SORBS1 and LPAR1. In brief, through multiple analytical methods, we found that miR-205 and the GCPR module play critical roles in GC progression. In addition, miR-205 might maintain cell adhesion by regulating SORBS1 and LPAR1. To screen the potential drug candidates, the gene expression profile of the GCPR module was mapped connectivity map (Cmap), and the mTOR inhibitor (Sirolimus) was found to be the most promising candidate. We further confirmed that Sirolimus can suppress cell proliferation of GC cell in vitro.

β-inducible gene-h3 promotes human breast carcinoma cell metastasis by activating the phosphatidylinositol 3-kinase/protein kinase B signaling pathway

Metastatic breast cancer is one of the most common metastatic tumors. Although studies have validated the role of β-inducible gene-h3 (βig-h3) in human biology and disease, the detailed mechanisms mediated by βig-h3 in breast carcinoma metastasis remain unclear. Thus, the present study investigated the role and potential mechanism of βig-h3 during breast carcinoma cell metastasis. The results indicated that the upregulation of βig-h3 significantly promotes the growth and inhibits the cisplatin-induced apoptosis of breast carcinoma cells. It was also demonstrated that βig-h3 promoted the migration and invasion of human breast carcinoma cells in vitro and in vivo. Furthermore, the results demonstrated that βig-h3 upregulated the overall expression and phosphorylation of phosphatidylinositol 3-kinase (PI3K) and protein kinase B (Akt) in human breast carcinoma cells. By contrast, βig-h3 knockdown reversed the βig-h3-mediated characteristics of breast carcinoma cells. Thus, the current study demonstrated that the PI3K/Akt signaling pathway serves a role in βig-h3-induced human breast cancer cell metastasis and that βig-h3 transfection enhances the metastatic potential of human breast carcinoma cells via the PI3K/Akt signaling pathway. These observations contribute to the understanding of the potential mechanism of human breast carcinoma cell growth and metastasis and suggest that βig-h3 may be a promising therapeutic target for the treatment of human breast carcinoma.

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.

Adhesion molecules in peritoneal dissemination: function, prognostic relevance and therapeutic options

Peritoneal dissemination is diagnosed in 10–25 % of colorectal cancer patients. Selected patients are treated with cytoreductive surgery and hyperthermic intraperitoneal chemotherapy. For these patients, earlier diagnosis, optimised selection criteria and a personalised approach are warranted. Biomarkers could play a crucial role here. However, little is known about possible candidates. Considering tumour cell adhesion as a key step in peritoneal dissemination, we aim to provide an overview of the functional importance of adhesion molecules in peritoneal dissemination and discuss the prognostic, diagnostic and therapeutic options of these candidate biomarkers. A systematic literature search was conducted according to the PRISMA guidelines. In 132 in vitro, ex vivo and in vivo studies published between 1995 and 2013, we identified twelve possibly relevant adhesion molecules in various cancers that disseminate peritoneally. The most studied molecules in tumour cell adhesion are integrin α2β1, CD44 s and MUC16. Furthermore, L1CAM, EpCAM, MUC1, sLe^x and Le^x, chemokine receptors, Betaig-H3 and uPAR might be of clinical importance. ICAM1 was found to be less relevant in tumour cell adhesion in the context of peritoneal metastases. Based on currently available data, sLe^a and MUC16 are the most promising prognostic biomarkers for colorectal peritoneal metastases that may help improve patient selection. Different adhesion molecules appear expressed in haematogenous and transcoelomic spread, indicating two different attachment processes. However, our extensive assessment of available literature reveals that knowledge on metastasis-specific genes and their possible candidates is far from complete.

Exosomal miRNAs from Peritoneum Lavage Fluid as Potential Prognostic Biomarkers of Peritoneal Metastasis in Gastric Cancer

Peritoneal metastasis is the most frequent type of recurrence in patients with gastric cancer (GC) and is associated with poor prognosis. Peritoneal lavage cytology, used to evaluate the risk of peritoneal metastasis, has low sensitivity. Here, we assessed the diagnostic potential of exosomal miRNA profiles in peritoneal fluid for the prediction of peritoneal dissemination in GC. Total RNA was extracted from exosomes isolated from six gastric malignant ascites (MA) samples, 24 peritoneal lavage fluid (PLF) samples, and culture supernatants (CM) of two human gastric carcinoma cell lines that differ in their potential for peritoneal metastasis. Expression of exosomal miRNAs was evaluated with Agilent Human miRNA microarrays and quantitative reverse transcription polymerase chain reaction (qRT-PCR). The microarray analysis indicated a low variability in the number and signal intensity of miRNAs detected among the samples. In the six MA fluids, miR-21 showed the highest signal intensity. We identified five miRNAs (miR-1225-5p, miR-320c, miR-1202, miR-1207-5p, and miR-4270) with high expression in MA samples, the PLF of serosa-invasive GC, and the CM of a highly metastatic GC cell line; these candidate miRNA species appear to be related to peritoneal dissemination. Differential expression of miR-21, miR-320c, and miR-1225-5p was validated in the PLF of serosa-invasive and non-invasive GC by qRT-PCR and miR-21 and miR-1225-5p were confirmed to be associated with serosal invasion in GC. PLF can be used to profile the expression of exosomal miRNAs. Our findings suggest that miR-21 and miR-1225-5p may serve as biomarkers of peritoneal recurrence after curative GC resection, thus providing a novel approach to early diagnosis of peritoneal dissemination of GC.

Expression of RNF180 and RECK in gastric carcinoma

AIM: To detect the expression of ring finger protein 180 (RNF180) and reversion-inducing-cysteine-rich protein with Kazal motifs (RECK) in gastric carcinoma.

METHODS: Western blot and reverse transcription-polymerase chain reaction (RT-PCR) were used to detect the expression of RECK and RNF180 in gastric cancer, pericarcinomatous tissue and normal gastric mucosal tissue.

RESULTS: The positive rates of RNF180 expression in gastric cancer and pericarcinomatous tissue were significantly lower than that in normal gastric mucosal tissue (68.7%, 28.4% vs 6.1%, P < 0.05). RECK expression was significantly lower in gastric carcinoma and pericarcinomatous tissue than in normal gastric mucosal tissue (71.4%, 31.6% vs 5.3%, P < 0.05).

CONCLUSION: RNF180 and RECK expression in gastric cancer is significantly reduced, suggesting that they may play an important role in the development of gastric cancer.

Prediction of peritoneal recurrence by the mRNA level of CEA and MMP-7 in peritoneal lavage of gastric cancer patients

A number of tumor markers had been reported to be useful in detecting free cancer cells in the peritoneal cavity and predict peritoneal recurrence in gastric cancer patients. The objective of this study was to compare the clinical impact of different tumor markers in peritoneal lavage fluid using the real-time quantitative reverse transcription polymerase chain reaction (RT-PCR) technique and to screen the most effective ones from them. The peritoneal lavage fluid of 116 patients with gastric cancer was sampled at laparotomy. After RNA extraction and reverse transcription, real-time quantitative polymerase chain reaction (PCR) was performed using the primers and probes for carcinoembryonic antigen (CEA), cytokeratin-20, matrix metalloproteinase-7 (MMP-7), carbohydrate antigen 125, and transforming growth factor-beta-1. Among the 116 patients, 45 (38.8%) were confirmed to have peritoneal recurrence. Any of the PCR-positive results of the five tumor markers could predict peritoneal recurrence in the univariate analysis (P < 0.001). In the multivariate analysis, the PCR results of CEA (P = 0.003) and MMP-7 (P = 0.028) were found to be independent prognostic factors. A real-time quantitative RT-PCR analysis of the CEA and MMP-7 transcripts in peritoneal lavage fluid could effectively predict peritoneal recurrence in advanced gastric cancer patients who underwent a potentially curative resection.

BIGH3 modulates adhesion and migration of hematopoietic stem and progenitor cells

Cell adhesion and migration are important determinants of homing and development of hematopoietic stem and progenitor cells (HSPCs) in bone marrow (BM) niches. The extracellular matrix protein transforming growth factor-β (TGF-β) inducible gene H3 (BIGH3) is involved in adhesion and migration, although the effect of BIGH3 is highly cell type-dependent. BIGH3 is abundantly expressed by mesenchymal stromal cells, while its expression in HSPCs is relatively low unless induced by certain BM stressors. Here, we set out to determine how BIGH3 modulates HSPC adhesion and migration. We show that primary HSPCs adhere to BIGH3-coated substrates, which is, in part, integrin-dependent. Overexpression of BIGH3 in HSPCs and HL60 cells reduced the adhesion to the substrate fibronectin in adhesion assays, which was even more profound in electrical cell-substrate impedance sensing (ECIS) assays. Accordingly, the CXCL12 induced migration over fibronectin-coated surface was reduced in BIGH3-expressing HSPCs. The integrin expression profile of HSPCs was not altered upon BIGH3 expression. Although expression of BIGH3 did not alter actin polymerization in response to CXCL12, it inhibited the PMA-induced activation of the small GTPase RAC1 as well as the phosphorylation and activation of extracellular-regulated kinases (ERKs). Reduced activation of ERK and RAC1 may be responsible for the inhibition of cell adhesion and migration by BIGH3 in HSPCs. Induced BIGH3 expression upon BM stress may contribute to the regulation of BM homeostasis.

Inhibition of gastric cancer cell growth and invasion through siRNA-mediated knockdown of guanine nucleotide exchange factor Vav3

Vav3, a Rho GTPase guanine nucleotide exchange factor, is associated with tumor growth, apoptosis, invasion and metastasis, and angiogenesis. However, the role of Vav3 in gastric cancer remains unclear. In this study, Vav3 expression was blocked by specific siRNA in gastric cancer cell line MGC803. MTT was used to assay cell proliferation activity; wound healing assay and transwell assay were applied to detect cell migration and invasion ability; and qRT-PCR and Western blot were employed to detect expression levels of Vav3 as well as proliferation, migration, and invasion-related genes. The results showed that Vav3 expression in gastric cancer tissues and cell lines was significantly upregulated and was higher than that in adjacent tissues of cancer and normal gastric mucosal cell lines. Vav3 knockdown inhibited proliferation, migration, and invasion of MGC803 gastric cancer cells. The expression of P21, P27, TIMP-1, and TIMP-2 was upregulated, while proliferating cell nuclear antigen, cyclin E1, matrix metalloproteinase (MMP)-2, and MMP-7 were downregulated by Vav3 knockdown in MGC803 gastric cells. In conclusion, Vav3 is involved in the proliferation, migration, and invasion of gastric cancer cell as a tumor oncogene.

Milky spot macrophages remodeled by gastric cancer cells promote peritoneal mesothelial cell injury

Peritoneal dissemination (PD) is the most frequent metastatic pattern of advanced gastric cancer (GC) and the main cause of death in GC patients. Human peritoneal mesothelial cell (HPMC) injury induced by gastric cancer cells (GCCs) and GCC outgrowths supported by peritoneal milky spot macrophages (PMSMs) are the key events during gastric cancer peritoneal dissemination (GCPD). In this study, we investigated whether PMSMs remodeled by GCC can induce HPMC injury and create a favorable microenvironment for GCPD. We established a tumor-associated macrophage (TAM) model using in vitro cell coculture. Normal macrophages cocultured with GCCs down-regulated expression of antigen-presenting surface molecules CD80, CD86, and MHC-II, but, notably, they up-regulated expression of phagocytic scavenger receptor CD206, which is similar to the M2 macrophage phenotype. In further experiments, various experimental methods were applied to detect the injurious effect of TAMs on HPMCs in another TAM-HPMC coculture. Our results showed that GCCs can induce HPMC apoptosis by unregulated apoptosis associated with cleaved caspase3, cleaved caspase9, and p21 proteins. HPMC growth ceased, and both early- and late-stage apoptosis were observed. Additionally, GCCs can induce HPMC fibrosis via increased expression of epithelial cell marker E-cadherin and decreased expression of mesenchymal cell marker α-SMA. Our results demonstrate that, in the GCPD process, PMSMs were remodeled by GCCs, resulting in phenotypic and functional transformation. In turn, this transformation induced HPMC injury and provided a favorable microenvironment for GCC anchorage and growth. These results may provide new insight into the mechanisms of GCPD.