Molecular diagnosis and therapy for occult peritoneal metastasis in gastric cancer patients

Harnessing the supremacy of MEG3 LncRNA to defeat gastrointestinal malignancies

Evidence suggests that long non-coding RNAs (lncRNAs) play a pivotal role in the carcinogenesis and progression of various human malignancies including gastrointestinal malignancies. This comprehensive review reports the functions and mechanisms of the lncRNA maternally expressed gene 3 (MEG3) involved in gastrointestinal malignancies. It summarizes its roles in mediating the regulation of cellular proliferation, apoptosis, migration, invasiveness, epithelial-to-mesenchymal transition, and drug resistance in several gastrointestinal cancers such as colorectal cancer, gall bladder cancer, pancreatic cancer, gastric cancer, esophageal cancer, cholangiocarcinoma, gastrointestinal stromal tumors and most importantly, hepatocellular carcinoma. In addition, the authors briefly highlight its implicated mechanistic role and interactions with different non-coding RNAs and oncogenic signaling cascades. This review presents the rationale for developing non coding RNA-based anticancer therapy via harnessing the power of MEG3 in gastrointestinal malignancies.

Utility of Molecular Analysis of Peritoneal Fluid in Staging Laparoscopy of Advanced Esophagogastric Junction and Gastric Cancer Prior to Neoadjuvant Treatment

PURPOSE

Molecular analysis of peritoneal fluid in staging laparoscopy of gastric cancer is performed to improve the detection of free intraperitoneal tumor cells. Nevertheless, its significance is controversial, especially in patients with negative cytology but positive molecular analysis. The aim of this study was to analyze the sensitivity of molecular analysis and its prognostic value.

METHODS

A retrospective analysis from April 2011 to October 2019 was performed. Cytology (Cyt) and molecular analysis were analyzed by real-time reverse transcriptase polymerase chain reaction (RT-PCR) of the carcinoembryonic antigen (CEA) and cytokeratin 20 (CK20) tumor makers.

RESULTS

During the study period, 138 staging laparoscopies were performed. Macroscopic carcinomatosis was found in 12.3%. Of the remaining 87.7%, 9.9% were Cyt + and 11.6% were Cyt- RT-PCR + . Of the latter, 9 responded to chemotherapy and underwent radical surgery. The sensitivity of cytology and molecular analysis was 0.70 and 0.76, respectively (p = 0.67). The 2-year overall survival (OS) of Cyt- RT-PCR + vs. Cyt + was similar (p = 0.1). The 2-year OS of Cyt-RT-PCR + subgroup who underwent radical surgery vs. Cyt-RT-PCR- patients was similar (p = 0.69), but disease-free survival was shorter in the first group (p = 0.005).

CONCLUSION

Our results show that the sensitivity of molecular analysis is similar to that of cytology. The prognostic value of positive molecular analysis was similar to positive cytology in terms of 2-year overall survival, except in the subgroup of operated patients in whom the overall survival was similar to that of those with a negative molecular analysis, albeit with a shorter disease-free survival.

Accurate and Rapid Detection of Peritoneal Metastasis from Gastric Cancer by AI-Assisted Stimulated Raman Molecular Cytology

Peritoneal metastasis (PM) is the mostcommon form of distant metastasis and one of the leading causes of death in gastriccancer (GC). For locally advanced GC, clinical guidelines recommend peritoneal lavage cytology for intraoperative PM detection. Unfortunately, current peritoneal lavage cytology is limited by low sensitivity (<60%). Here the authors established the stimulated Raman molecular cytology (SRMC), a chemical microscopy-based intelligent cytology. The authors firstly imaged 53 951 exfoliated cells in ascites obtained from 80 GC patients (27 PM positive, 53 PM negative). Then, the authors revealed 12 single cell features of morphology and composition that are significantly different between PM positive and negative specimens, including cellular area, lipid protein ratio, etc. Importantly, the authors developed a single cell phenotyping algorithm to further transform the above raw features to feature matrix. Such matrix is crucial to identify the significant marker cell cluster, the divergence of which is finally used to differentiate the PM positive and negative. Compared with histopathology, the gold standard of PM detection, their SRMC method could reach 81.5% sensitivity, 84.9% specificity, and the AUC of 0.85, within 20 minutes for each patient. Together, their SRMC method shows great potential for accurate and rapid detection of PM from GC.

Prognostic value of molecular cytology by one-step nucleic acid amplification (OSNA) assay of peritoneal washings in advanced gastric cancer patients

Peritoneal dissemination is a common form of gastric cancer (GC) recurrence, despite surgery with curative intent. This study aimed to evaluate the prognostic value of intraperitoneal lavage One-Step Nucleic Acid Amplification (OSNA) assay in advanced GC patients. OSNA assay targeting CK-19 mRNA was applied to detect free cancer cells (FCC) in intraperitoneal lavage samples obtained during gastrectomy. A total of 82 GC patients were enrolled to investigate the correlation between OSNA assay and patient's prognosis. Of the 82 patients, OSNA assay was positive in 25 (30.5%) patients. The median OS in OSNA positive patients was significantly lower than in OSNA negative patients (19 vs 45 months). Positive OSNA assay result was a significant unfavourable prognostic factor in both, univariable (HR 3.45, 95% CI 0.95-12.48; p = 0.0030) and multivariable analysis (HR 3.10, 95% CI 1.22-8.54; p = 0.0298). Positive OSNA assay in intraperitoneal lavage is a valuable indicator of poor survival in advanced GC patients after multimodal treatment. After further confirmation on larger sample size, OSNA assay of peritoneal washings could be considered an adjunct tool to conventional cytology, the current gold standard, to provide precise intraoperative staging and additional prognostic information.

MiR-139-5p Inhibits the Development of Gastric Cancer through Targeting TPD52

BACKGROUND

Many researchers have confirmed that miRNAs are involved in the pathogenesis of gastric cancer (GC). This study focused on investigating the specific functions of miR-139-5p in GC.

METHODS

MiR-139-5p and TPD52 expressions were observed by qRT-PCR or western blot in GC. The functional mechanism of miR-139-5p was explored by the luciferase reporter assay, transwell assay, and MTT assay.

RESULTS

MiR-139-5p downregulation and TPD52 upregulation were detected in GC. Adverse clinical features and prognosis in GC patients were related to low miR-139-5p expression. MiR-139-5p overexpression restrained GC cell proliferation and metastasis. Furthermore, miR-139-5p directly targeted TPD52. TPD52 silencing blocked GC progression. And TPD52 upregulation weakened the antitumor effect of miR-139-5p in GC.

CONCLUSION

MiR-139-5p inhibits GC cell proliferation and metastasis through downregulating TPD52.

STAT3 promotes peritoneal metastasis of gastric cancer by enhancing mesothelial-mesenchymal transition

Signal transducer and activator of transcription 3 (STAT3) is a widely-reported oncogene in many human cancers, but its role in the peritoneal metastasis of gastric cancer (GC) has yet to be studied. The expression level of STAT3 in GC patient tissues was assessed. Stable shRNA knockdown (KD) of STAT3 was established in GC cell line AGS, followed by examination of its effect on AGC cell viability and proliferation, xenograft tumor growth, metastatic potential, mesothelial-to-mesenchymal transition (MMT)-related properties and peritoneal metastasis in a mouse model. The specific STAT3 inhibitor BP1-102 was also employed to verify findings from STAT3 KD experiments. Expression of activated STAT3 was upregulated in GC patient tumor tissues, and further elevated among patients diagnosed with peritoneal metastasis. STAT3 deactivation suppressed viability and proliferation of GC cells in vitro, as well as GC tumorigenesis in vivo. Furthermore, the metastatic properties and production of MMT-inducing factors of GC cells in vitro were also dependent on STAT3 activation. Importantly, STAT3 KD significantly compromised peritoneal metastasis of GC in vivo. STAT3 activation contributes to peritoneal metastasis of GC by promoting MMT, warranting further investigation to explore its potential for GC treatment, in particular among peritoneal metastasis patients.

A nomogram based on glycomic biomarkers in serum and clinicopathological characteristics for evaluating the risk of peritoneal metastasis in gastric cancer

Background

Peritoneal metastasis (PM) in gastric cancer (GC) remains an untreatable disease, and is difficult to diagnose preoperatively. Here, we aim to establish a novel prediction model.

Methods

The clinicopathologic characteristics of a cohort that included 86 non-metastatic GC patients and 43 PMGC patients from Zhongshan Hospital were retrospectively analysed to identify PM associated variables. Additionally, mass spectrometry and glycomic analysis were applied in the same cohort to find glycomic biomarkers in serum for the diagnosis of PM. A nomogram was established based on the associations between potential risk variables and PM.

Results

Overexpression of 4 N-glycans (H6N5L1E1: m/z 2620.93; H5N5F1E2: m/z 2650.98; H6N5E2, m/z 2666.96; H6N5L1E2, m/z 2940.08); weight loss ≥ 5 kg; tumour size ≥ 3 cm; signet ring cell or mucinous adenocarcinoma histology type; poor differentiation; diffuse or mixed Lauren classification; increased CA19-9, CA125, and CA724 levels; decreased lymphocyte count, haemoglobin, albumin, and pre-albumin levels were identified to be associated with PM. A nomogram that integrated with five independent risk factors (weight loss ≥ 5 kg, CA19-9 ≥ 37 U/mL, CA125 ≥ 35 U/mL, lymphocyte count < 2.0 * 10 ~ 9/L, and H5N5F1E2 expression ≥ 0.0017) achieved a good performance for diagnosis (AUC: 0.892, 95% CI 0.829–0.954). When 160 was set as the cut-off threshold value, the proposed nomogram represented a perfectly discriminating power for both sensitivity (0.97) and specificity (0.88).

Conclusions

The nomogram achieved an individualized assessment of the risk of PM in GC patients; thus, the nomogram could be used to assist clinical decision-making before surgery.

Predicting Peritoneal Dissemination of Gastric Cancer in the Era of Precision Medicine: Molecular Characterization and Biomarkers

Gastric cancer (GC) is a leading cause of worldwide cancer-related death. Being a highly heterogeneous disease, the current treatment of GC has been suboptimal due to the lack of subtype-dependent therapies. Peritoneal dissemination (PD) is a common pattern of GC metastasis associated with poor prognosis. Therefore, it is urgently necessary to identify patients at high risk of PD. PD is found to be associated with Lauren diffuse type GC. Molecular profiling of GC, especially diffuse type GC, has been utilized to identify molecular alterations and has given rise to various molecular classifications, shedding light on the underlying mechanism of PD and enabling identification of patients at higher PD risk. In addition, a series of diagnositc and prognostic biomarkers of PD from serum, peritoneal lavages and primary GCs have been reported. This comprehensive review summarizes findings on the multi-omic characteristics of diffuse type GC, the clinical significance of updating molecular classifications of GC in association with PD risk and research advances in PD-associated biomarkers.

Primary tumor types and origins in positive abdominopelvic washing cytology, a single institution experience

INTRODUCTION

Abdominopelvic washing cytology is a common specimen evaluated for ovarian, fallopian tubal, and peritoneal cancer staging or other nongynecologic malignancies presented as metastases. We reviewed our experience in diagnosing abdominopelvic washing specimens and assessing the primary tumor types and origins of the positive abdominopelvic washings.

MATERIALS AND METHODS

A pathology archive database search was performed for abdominopelvic washing specimens from 2007 to 2018. The corresponding cytologic diagnoses, results of ancillary studies, clinical histories, and surgical follow-up were reviewed. The primary sites were determined based on the synoptic reports, when available.

RESULTS

A total of 5.8% (350 of 6023) of cases were positive for malignancy or neoplasm. Additionally, 1.3% (78 of 6023) were diagnosed as atypical cells. Of the 350 positive cases, 93.4% were müllerian tumors. The frequency of primary sites for müllerian tumors in descending order were: ovary, uterus, fallopian tube, peritoneum, and uncertain müllerian sites. The common ovarian tumors identified in pelvic washing in descending order were: high-grade serous carcinoma, serous borderline tumor, clear cell carcinoma, low-grade serous carcinoma, and endometrioid carcinoma. Gastrointestinal, breast, bladder, and lymphoma primaries were the 23 nongynecologic tumors identified in pelvic washings.

CONCLUSIONS

Positive findings in abdominopelvic washing cytology is rare. The majority of the positive cases were from müllerian origins, with ovary and uterus as the most common sites. Endometrial adenocarcinoma, endometrioid type and ovarian high-grade serous carcinoma were the most common tumor types. Knowing prior history of malignancy, morphologic comparison with concurrent surgical cases, and performing ancillary studies are keys to improve diagnostic accuracy of abdominopelvic washings.

TRIM58 suppresses the tumor growth in gastric cancer by inactivation of β-catenin signaling via ubiquitination

Objective: To investigate and define the underlying molecular mechanism of tripartite motif-containing 58 (TRIM58) in regulating the tumor growth of gastric cancer (GC).Methods: TRIM58 expression in GC tissues and cells was detected by real-time PCR and Western blot, followed by lentiviral-induced overexpression or knockdown of TRIM58. Subsequently, CCK8, BrdU-ELISA, flow cytometry, immunoprecipitation, in vitro animal experiments and immunochemistry were performed to explore the function of TRIM58. Western blotting was used to detect β-catenin, C-myc, Cyclin D1, and survivin expression.Results: TRIM58 expression was significantly reduced in tumor tissues of GC patients and GC cell lines, whereas β-catenin, C-myc, Cyclin D1, and survivin were highly expressed. Overexpression of TRIM58 in GC cells resulted in decreases in β-catenin, C-myc, Cyclin D1, and survivin protein expression and significantly suppressed proliferation by preventing cell-cycle progression and promoting cell apoptosis. Conversely, TRIM58 knockdown resulted in the opposite effects. Furthermore, the effect of TRIM58 knockdown on GC cells was potently reversed by a β-catenin inhibitor, XAV939. Immunoprecipitations showed the interaction between TRIM58 and β-catenin, and TRIM58 overexpression significantly enhanced β-catenin degradation. In addition, we found a significant decrease in the growth and weight of tumors and an increase in tumor cell apoptosis in TRIM58-overexpression nude mice, which were also accompanied by reduced β-catenin expression.Conclusions: These data suggest that TRIM58 may function as a tumor suppressor in GC and potentially suppress the tumor growth of gastric cancer by inactivation of β-catenin signaling via ubiquitination.

Novel Tumor Suppressor lncRNA Growth Arrest-Specific 5 (GAS5) In Human Cancer

Long noncoding RNAs (lncRNAs) play crucial regulatory roles in fundamental biological processes, and deregulations of lncRNAs have been linked to numerous human diseases, especially cancers. Of particular interest in this regard is lncRNA GAS5, which is mainly identified as a tumor suppressor in several cancers. GAS5 was significantly low expressed in multiple cancers and was associated with clinic-pathological characteristics and patient survival, indicating a novel potential diagnostic and prognostic biomarker, and a therapeutic target for cancer. Functionally, GAS5 is involved in cell proliferation, metastasis, invasion, apoptosis, epithelial-mesenchymal transition (EMT), and drug resistance, among others, via multiple molecular mechanisms, such as binding to DNA sequences, forming RNA-DNA triplex complex, triggering or suppressing the expression of genes, binding proteins to form chromatin-modifying complex, which activates or represses gene expression, and acting as miRNA sponge to suppress miRNA expression, leading to regulation of miRNA target genes. This review provides an overview of the current state of knowledge and role of GAS5 in clinical relevance, biological functions and molecular mechanisms underlying the dysregulation of expression and function of GAS5 in cancer. Finally, the potential prospective role as diagnostic and prognostic biomarker and therapeutic target in cancer is discussed.

LncRNA LINC01116 Promotes Cancer Cell Proliferation, Migration And Invasion In Gastric Cancer By Positively Interacting With lncRNA CASC11

Purpose

The oncogenic roles of lncRNA LINC01116 have been reported in several types of cancer, while its involvement in gastric cancer is unknown. This study aimed to investigate the involvement of LINC01116 in gastric cancer.

Methods

Gene expression was detected by qPCR. Correlations were analyzed by linear regression. Overexpression and siRNA silencing techniques were used to analyze gene functions. Cell invasion and migration were analyzed by Transwell assays.

Results

LINC01116 and lncRNA CASC11 were both upregulated in cancer tissues compared to cancer-adjacent tissues. Expression levels of LINC01116 and CASC11 were increased with the increase in clinical stages. Expression levels of LINC01116 and CASC11 were positively correlated. Overexpression of LINC01116 mediated the upregulated CASC11 in gastric cancer cells, and CASC11 overexpression also led to overexpressed LINC01116. Overexpression of LINC01116 and CASC11 led to promoted invasion and migration of gastric cancer cells. Rescue experiments showed that CASC11 knockdown attenuated the effects of LINC01116 overexpression. Overexpression of LINC01116 failed to significantly affect cancer cell proliferation.

Conclusion

LINC01116 promoted cancer cell invasion and migration in gastric cancer by positively interacting with CASC11.

Integrated fluorescent cytology with nano-biologics in peritoneally disseminated gastric cancer

Gastric cancer patients positive for peritoneal cytology are at increased risk of tumor recurrence, but although a certain proportion of cytology‐positive patients relapse rapidly with aggressive progression, others survive longer with conventional chemotherapies. This heterogeneity makes it difficult to stratify patients for more intensive therapy and poses a substantial challenge for the implementation of precision medicine. We developed a new approach to identify biologically malignant subpopulations in cytology‐positive gastric cancer patients, using a green fluorescent protein (GFP)‐expressing attenuated adenovirus in which the telomerase promoter regulates viral replication (TelomeScan, OBP‐401). The fluorescence emitted from TelomeScan‐positive cells was successfully quantified using a multi‐mode microplate reader. We then analyzed clinical peritoneal washes obtained from 68 gastric cancer patients and found that patients positive for TelomeScan had a significantly worse prognosis. In 21 cytology‐positive patients, the median survival time of those who were TelomeScan positive (235 days) was significantly shorter than that for those who were TelomeScan negative (671 days; P = 0.0062). This fluorescent virus‐guided cytology detects biologically malignant cancer cells from the peritoneal washes of gastric cancer patients and may thus be useful for both therapy stratification and precision medicine approaches based on genetic profiling of disseminated cells.

Long non-coding RNA AB007962 is downregulated in gastric cancer and associated with poor prognosis

A number of previous studies have reported that numerous long non-coding RNAs (lncRNAs) are dysregulated in gastric cancer (GC) and are involved in a series of biological and pathological processes. Total RNA was extracted from the cancerous tissues and matched normal adjacent tissues (NATs) of 96 patients with GC. The expression level of AB007962, a novel lncRNA, was determined by reverse transcription-quantitative polymerase chain reaction. The association between AB007962 expression levels and clinicopathological features were analyzed. Kaplan-Meier curves were also constructed in order to evaluate prognosis. Finally, publicly accessible data from The Cancer Genome Atlas was used to further verify the expression levels and clinical significance of AB007962. In conclusion, it was determined that the expression level of AB007962 was significantly reduced, compared with matched NATs in GC tissues (P=0.003). Survival analysis indicated that patients with intestinal-type GC with a reduced expression of AB007962 had a reduced prognosis, compared with those with an increased expression. AB007962 may be involved in the progression of GC and act as a novel prognostic biomarker for patients with GC, particularly in intestinal-type GC.

TRIM32 promotes cell proliferation and invasion by activating β-catenin signalling in gastric cancer

The tripartite motif (TRIM) family comprises more than 70 members involved in the regulation of many cellular pathways. TRIM32 acts as an E3 ubiquitin ligase and has been reported to participate in many human cancers. Here, we aimed to investigate the role of TRIM32 in gastric cancer (GC) and the clinical implications. High expression of TRIM32 was observed in GC tissues and cell lines, and was significantly associated with poor prognosis. Knockdown TRIM32 expression remarkably suppressed the proliferation, migration, and invasion of GC cells in vitro and tumour growth in vivo, whereas overexpression of TRIM32 yielded the opposite results. Western blotting and quantitative reverse‐transcription PCR (qRT‐PCR) analyses revealed that up‐regulation of TRIM32 significantly enhanced expression of β‐catenin protein and of its downstream targets TCF1, cyclin D1, Axin2 and MMP7 mRNAs. Moreover, we found that the mechanism behind the TRIM32‐promoted GC progression was related to the β‐catenin signalling pathway. Collectively, these data suggest that TRIM32 promotes GC cell proliferation, migration, and invasion by activating the β‐catenin signalling pathway.

Tanshinone IIA inhibits cell proliferation and tumor growth by downregulating STAT3 in human gastric cancer

Gastric cancer is the third leading cause of cancer-associated deaths worldwide. Research into the underlying mechanisms of gastric cancer is essential for the development of novel therapeutic agents to improve the prognoses of patients with gastric cancer. Tanshinone IIA (Tan IIA) is the pure extract of Danshen root (Salvia miltiorrhiza) and has been report to inhibit the proliferation of gastric cancer cells; however, the intrinsic underlying mechanisms remain unclear. The aim of the present study was to investigate whether Tan IIA has a direct anti-cancer effect in gastric cancer cells and determine the underlying mechanisms responsible. The results revealed that Tan IIA effectively inhibits proliferation in three human gastric cancer cell lines (SNU-638, MKN1 and AGS) in a time- and dose-dependent manner. Furthermore, Tan IIA treatment induced an increase in apoptosis, B-cell lymphoma (Bcl-2)-associated protein X expression and cleaved caspase-3 levels, as well as a decrease in Bcl-2 expression. Treatment with Tan IIA inhibited Furthermore, treatment with Tan IIA significantly inhibited the phosphorylation of signal transducer and activator of transcription 3 (STAT3), which may be responsible for the changes in apoptosis gene expression. However, overexpression of STAT3 significantly ameliorated the Tan IIA-induced suppression of cell growth and apoptosis. A nude mouse xenograft model was constructed and the results revealed that intraperitoneal Tan IIA treatment for 28 days significantly inhibited tumor growth and STAT3 activation. The results of the present study suggest that Tan IIA exerts potent anti-cancer activity in gastric cancer cells and this effect is mediated by the downregulation of STAT3 activation.

The GAS5/miR-222 Axis Regulates Proliferation of Gastric Cancer Cells Through the PTEN/Akt/mTOR Pathway

BACKGROUND

Several lines of evidence have indicated that growth arrest-specific transcript 5 (GAS5) functions as a tumor suppressor and is aberrantly expressed in multiple cancers. GAS5 was found to be downregulated in gastric cancer (GC) tissues, and ectopic expression of GAS5 inhibited GC cell proliferation.

AIMS

The present study aimed to explore the underlying mechanisms of GAS5 involved in GC cell proliferation.

METHODS

GAS5 and miR-222 expressions in GC cell lines were estimated by quantitative real-time polymerase chain reaction. The effects of GAS5 and miR-222 on GC cell proliferation were assessed by MTT assay and 5-bromo-2-deoxyuridine (BrdU) incorporation assays. The interaction between GAS5 and miR-222 was confirmed by luciferase reporter assay and RNA immunoprecipitation assay. The protein levels of the phosphatase and tensin homolog (PTEN), phosphorylated protein kinase B (Akt) (p-Akt), Akt, phosphorylated mammalian target of rapamycin (mTOR) (p-mTOR), and mTOR were determined by western blot.

RESULTS

GAS5 was downregulated and miR-222 was upregulated in GC cells. GAS5 directly targeted and suppressed miR-222 expression. GAS5 overexpression and miR-222 inhibition suppressed cell proliferation, increased PTEN protein level and decreased p-Akt and p-mTOR protein levels in GC cells while GAS5 knockdown and miR-222 overexpression exhibited the opposite effects. Moreover, mechanistic analyses revealed that GAS5 regulated GC cell proliferation through the PTEN/Akt/mTOR pathway by negatively regulating miR-222.

CONCLUSIONS

GAS5/miR-222 axis regulated proliferation of GC cells through the PTEN/Akt/mTOR pathway, which facilitated the development of lncRNA-directed therapy against this deadly disease.

Long Noncoding RNA Taurine-Upregulated Gene 1 Promotes Cell Proliferation and Invasion in Gastric Cancer via Negatively Modulating miRNA-145-5p

Long noncoding RNA (lncRNA) taurine-upregulated gene 1 (TUG1) is involved in the development and carcinogenesis of various tumors, suggesting the diagnostic potential of TUG1 in these cancers. However, the exact role of TUG1 and its underlying mechanism in gastric cancer (GC) remain unknown. In this study, the expression of TUG1 and miR-145-5p in GC cell lines and nonmalignant gastric epithelial cell lines was detected by qRT-PCR. BGC-823 and SGC-7901 cells were transfected with si-TUG1, pcDNA 3.1-TUG1, miR-145-5p mimics, or matched controls. The biological function of TUG1 and miR-145-5p in GC cell proliferation and invasion in vitro and tumor growth in vivo was investigated by MTT assay, Transwell invasion assay, and tumor xenograft experiments. The regulating relationship between TUG1 and miR-145-5 was confirmed by luciferase reporter assay. The results showed that TUG1 was significantly overexpressed and miR-145-5p was dramatically downregulated in GC cell lines. TUG1 knockdown strikingly inhibited cell proliferation and invasion in vitro and markedly suppressed tumor growth in vivo. Furthermore, TUG1 could directly bind to miR-145-5p and repress miR-145-5p expression. TUG1 overexpression significantly relieved the inhibition on GC cell proliferation and invasion in vitro and tumor growth in vivo, mediated by miR-145-5p overexpression. In conclusion, TUG1 promotes cell proliferation and invasion in GC via negatively modulating miRNA-145-5p, which undoubtedly contributes to understanding the mechanism of GC occurrence and development.

PRL-3 promotes the peritoneal metastasis of gastric cancer through the PI3K/Akt signaling pathway by regulating PTEN

Peritoneal metastasis is the most frequent cause of death in patients with advanced gastric carcinoma (GC). The phosphatase of regenerating liver-3 (PRL-3) is recognized as an oncogene and plays an important role in GC peritoneal metastasis. However, the mechanism of how PRL-3 regulates GC invasion and metastasis is unknown. In the present study, we found that PRL-3 presented with high expression in GC with peritoneal metastasis, but phosphatase and tensin homologue (PTEN) was weakly expressed. The p-PTEN/PTEN ratio was also higher in GC with peritoneal metastasis than that in the normal gastric tissues. We also found the same phenomenon when comparing the gastric mucosa cell line with the GC cell lines. After constructing a wild-type and a mutant-type plasmid without enzyme activity and transfecting them into GC SGC7901 cells, we showed that only PRL-3 had enzyme activity to downregulate PTEN and cause PTEN phosphorylation. The results also showed that PRL-3 increased the expression levels of MMP-2/MMP-9 and promoted the migration and invasion of the SGC7901 cells. Knockdown of PRL-3 decreased the expression levels of MMP-2/MMP-9 significantly, which further inhibited the migration and invasion of the GC cells. PRL-3 also increased the expression ratio of p-Akt/Akt, which indicated that PRL-3 may mediate the PI3K/Akt pathway to promote GC metastasis. When we transfected the PTEN siRNA plasmid into the PRL-3 stable low expression GC cells, the expression of p-Akt, MMP-2 and MMP-9 was reversed. In conclusion, our results provide a bridge between PRL-3 and PTEN; PRL-3 decreased the expression of PTEN as well as increased the level of PTEN phosphorylation and inactivated it, consequently activating the PI3K/Akt signaling pathway, and upregulating MMP-2/MMP-9 expression to promote GC cell peritoneal metastasis.

REG4 promotes peritoneal metastasis of gastric cancer through GPR37

Being the major reason of recurrence and death after surgery, peritoneal metastasis of gastric cancer dooms the prognosis of advanced gastric cancer patients. Regenerating islet-derived family, member 4 (REG4) is believed to promote peritoneal metastasis, however, its mechanism is still a moot point at present. In the present study, we show that high expression of REG4 correlates with advanced stage and poor survival prognosis for gastric cancer patients. REG4 overexpression significantly enhances peritoneal metastasis by increasing adhesion ability. Moreover, SP1 is proved to be a transcription factor of REG4 and induce REG4 expression upon TGF-alpha stimulation. Also, G protein-coupled receptor 37 (GPR37) is identified to be in the same complex of REG4, which mediates REG4's signal transduction and promotes peritoneal metastasis of gastric cancer cell. Interestingly, we also discover a positive feedback loop triggered by REG4, amplifying itself through EGFR transactivation, consisting of GPR37, ADAM17, TGF-alpha, EGFR, SP1 and REG4. In conclusion, REG4 promotes peritoneal metastasis of gastric cancer through GPR37 and triggers a positive feedback loop.

Gastric cancer: Current status of lymph node dissection

D2 procedure has been accepted in Far East as the standard treatment for both early (EGC) and advanced gastric cancer (AGC) for many decades. Recently EGC has been successfully treated with endoscopy by endoscopic mucosal resection or endoscopic submucosal dissection, when restricted or extended Gotoda's criteria can be applied and D1+ surgery is offered only to patients not fitted for less invasive treatment. Furthermore, two randomised controlled trials (RCTs) have been demonstrating the non inferiority of minimally invasive technique as compared to standard open surgery for the treatment of early cases and recently the feasibility of adequate D1+ dissection has been demonstrated also for the robot assisted technique. In case of AGC the debate on the extent of nodal dissection has been open for many decades. While D2 gastrectomy was performed as the standard procedure in eastern countries, mostly based on observational and retrospective studies, in the west the Medical Research Council (MRC), Dutch and Italian RCTs have been conducted to show a survival benefit of D2 over D1 with evidence based medicine. Unfortunately both the MRC and the Dutch trials failed to show a survival benefit after the D2 procedure, mostly due to the significant increase of postoperative morbidity and mortality, which was referred to splenopancreatectomy. Only 15 years after the conclusion of its accrual, the Dutch trial could report a significant decrease of recurrence after D2 procedure. Recently the long term survival analysis of the Italian RCT could demonstrate a benefit for patients with positive nodes treated with D2 gastrectomy without splenopancreatectomy. As nowadays also in western countries D2 procedure can be done safely with pancreas preserving technique and without preventive splenectomy, it has been suggested in several national guidelines as the recommended procedure for patients with AGC.

TRIM25 blockade by RNA interference inhibited migration and invasion of gastric cancer cells through TGF-β signaling

Tripartite Motif Containing 25 (TRIM25), a member of TRIM proteins, has been found abnormally expressed in cancers of female reproductive system. Here, TRIM25 was conspicuously expressed in human gastric cancer (GC) tissues in which its higher expression generally correlated with the poor prognosis of patients. Small interfering RNA (siRNA)-mediated knockdown of TRIM25 expression in MGC-803 and AGS cells had no effects on cell proliferation, whereas reduced cell migration and invasion. Gene set enrichment analysis on The Cancer Genome Atlas stomach adenocarcinoma (STAD) dataset revealed that several signaling pathways, including the migration, E-cadherin and transforming growth factor-β (TGF-β) pathways, were enriched in TRIM25 higher expression patients. Moreover, ectopic expression of TRIM25 in a GC cell line with lower expression of TRIM25 significantly promoted the migration and invasion. Further experiments with TGF-β inhibitor suggested that TRIM25 may exert its function through TGF-β pathway. In summary, our results indicate that TRIM25 acts as an oncogene in GC and thus presents a novel target for the detection and treatment of GC.

Diagnosis and treatment of peritoneal metastasis of gastric cancer

As the main reason of death in patients with gastric cancer, peritoneal metastasis is still a major problem to be solved. As we all know, peritoneal metastasis is the main form of advanced gastric cancer and gastric cancer recurrence, which involves a complex, multi-stage, multifactorial pathological process. The diagnosis and treatment of peritoneal metastasis of gastric cancer are particularly difficult. The good news is that through active exploration and clinical research, several important achievements have been made and gradually bring the gospel to clinical patients. This paper will review the recent progress in the diagnosis and treatment of peritoneal metastasis of gastric cancer.

Long non-coding RNA MEG3 functions as a competing endogenous RNA to regulate gastric cancer progression

Background

Long noncoding RNAs (lncRNAs) have recently emerged as important regulators in governing fundamental biological processes, and many of which are likely to have functional roles in tumorigenesis. Maternally expressed gene 3 (MEG3) gene encodes a lncRNA whose expression is lost in an expanding list of primary human tumors and tumor cell lines, however its biological role and regulatory mechanism in gastric cancer (GC) development and progression are poorly defined.

Methods

Quantitative RT-PCR analysis was used to determine whether aberrant MEG3 expression was associated with GC patients pTNM stage and pM state. Furthermore, the effect of ectopic expression of MEG3 on cell proliferation, migration, invasion and cell apoptosis was assessed by using CCK-8, wound healing, transwell invasion assays and flow cytometric analysis, respectively, in GC cell lines HGC-27 and MGC-803. Moreover, the competing endogenous RNA (ceRNA) activity of MEG3 on miR-181a was investigated via luciferase reporter assay and immunoblot analysis.

Results

MEG3 is decreased in GC patients and cell lines, and its expression was associated with metastatic GC. Furthermore, ectopic expression of MEG3 in HGC-27 and MGC-803 cells inhibited cell proliferation, migration, invasion, and promoted cell apoptosis, which might be due to MEG3 sequestering oncogenic miR-181 s in GC cells. Furthermore, MEG3 could up-regulated Bcl-2 via its competing endogenous RNA (ceRNA) activity on miR-181a.

Conclusions

These findings suggest that lncRNA MEG3, a ceRNA of miR-181 s, could regulate gastric carcinogenesis and may serve as a potential target for antineoplastic therapies.

Long non-coding RNA MEG3 functions as a competing endogenous RNA to regulate gastric cancer progression

BACKGROUND

Long noncoding RNAs (lncRNAs) have recently emerged as important regulators in governing fundamental biological processes, and many of which are likely to have functional roles in tumorigenesis. Maternally expressed gene 3 (MEG3) gene encodes a lncRNA whose expression is lost in an expanding list of primary human tumors and tumor cell lines, however its biological role and regulatory mechanism in gastric cancer (GC) development and progression are poorly defined.

METHODS

Quantitative RT-PCR analysis was used to determine whether aberrant MEG3 expression was associated with GC patients pTNM stage and pM state. Furthermore, the effect of ectopic expression of MEG3 on cell proliferation, migration, invasion and cell apoptosis was assessed by using CCK-8, wound healing, transwell invasion assays and flow cytometric analysis, respectively, in GC cell lines HGC-27 and MGC-803. Moreover, the competing endogenous RNA (ceRNA) activity of MEG3 on miR-181a was investigated via luciferase reporter assay and immunoblot analysis.

RESULTS

MEG3 is decreased in GC patients and cell lines, and its expression was associated with metastatic GC. Furthermore, ectopic expression of MEG3 in HGC-27 and MGC-803 cells inhibited cell proliferation, migration, invasion, and promoted cell apoptosis, which might be due to MEG3 sequestering oncogenic miR-181 s in GC cells. Furthermore, MEG3 could up-regulated Bcl-2 via its competing endogenous RNA (ceRNA) activity on miR-181a.

CONCLUSIONS

These findings suggest that lncRNA MEG3, a ceRNA of miR-181 s, could regulate gastric carcinogenesis and may serve as a potential target for antineoplastic therapies.

State-of-the-art methods in clinical diagnosis and treatment of peritoneal metastasis of gastric cancer

Gastric cancer is one of the most common malignant tumors and presents a very high mortality. The main reason for this situation is metastasis after curative resection, with the most common type being peritoneal metastasis, which accounts for more than 50% of all cases. Once peritoneal carcinomatosis (PC) happens, the pathological stage is stage IV and there is a grim prognosis. Accordingly, early effective prevention and treatment of PC have extremely important clinical significance for the improvement of the prognosis of patients with gastric cancer. This article describes the pathogenesis, clinical diagnosis using serum biomarkers and image examinations, as well as multimodality treatment of peritoneal metastasis of gastric cancer by neoadjuvant intraperitoneal-systemic chemotherapy (NIPS), cytoreductive surgery+hyperthermic intraperitoneal chemotherapy (CRS+HIPEC), early postoperative intraperitoneal chemotherapy (EPIC), extensive intraoperative peritoneal lavage (EIPL), molecular targeting therapy, and usage of drug delivery systems.