Molecular targeting to treat gastric cancer

Oncogenic structural aberration landscape in gastric cancer genomes

Structural variants (SVs) are responsible for driver events in gastric cancer (GC); however, their patterns and processes remain poorly understood. Here, we examine 170 GC whole genomes to unravel the oncogenic structural aberration landscape in GC genomes and identify six rearrangement signatures (RSs). Non-random combinations of RSs elucidate distinctive GC subtypes comprising one or a few dominant RS that are associated with specific driver events (BRCA1/2 defects, mismatch repair deficiency, and TP53 mutation) and epidemiological backgrounds. Twenty-seven SV hotspots are identified as GC driver candidates. SV hotspots frequently constitute complexly clustered SVs involved in driver gene amplification, such as ERBB2, CCNE1, and FGFR2. Further deconstruction of the locally clustered SVs uncovers amplicon-generating profiles characterized by super-large SVs and intensive segmental amplifications, contributing to the extensive amplification of GC oncogenes. Comprehensive analyses using adjusted SV allele frequencies indicate the significant involvement of extra-chromosomal DNA in processes linked to specific RSs.

Exosomes and cancer immunotherapy: A review of recent cancer research

As phospholipid extracellular vesicles (EVs) secreted by various cells, exosomes contain non-coding RNA (ncRNA), mRNA, DNA fragments, lipids, and proteins, which are essential for intercellular communication. Several types of cells can secrete exosomes that contribute to cancer initiation and progression. Cancer cells and the immune microenvironment interact and restrict each other. Tumor-derived exosomes (TDEs) have become essential players in this balance because they carry information from the original cancer cells and express complexes of MHC class I/II epitopes and costimulatory molecules. In the present study, we aimed to identify potential targets for exosome therapy by examining the specific expression and mechanism of exosomes derived from cancer cells. We introduced TDEs and explored their role in different tumor immune microenvironment (TIME), with a particular emphasis on gastrointestinal cancers, before briefly describing the therapeutic strategies of exosomes in cancer immune-related therapy.

Critical roles for EGFR and EGFR-HER2 clusters in EGF binding of SW620 human carcinoma cells

Epidermal growth factor (EGF) signalling regulates normal epithelial and other cell growth, with EGF receptor (EGFR) overexpression reported in many cancers. However, the role of EGFR clusters in cancer and their dependence on EGF binding is unclear. We present novel single-molecule total internal reflection fluorescence microscopy of (i) EGF and EGFR in living cancer cells, (ii) the action of anti-cancer drugs that separately target EGFR and human EGFR2 (HER2) on these cells and (iii) EGFR–HER2 interactions. We selected human epithelial SW620 carcinoma cells for their low level of native EGFR expression, for stable transfection with fluorescent protein labelled EGFR, and imaged these using single-molecule localization microscopy to quantify receptor architectures and dynamics upon EGF binding. Prior to EGF binding, we observe pre-formed EGFR clusters. Unexpectedly, clusters likely contain both EGFR and HER2, consistent with co-diffusion of EGFR and HER2 observed in a different model CHO-K1 cell line, whose stoichiometry increases following EGF binding. We observe a mean EGFR : EGF stoichiometry of approximately 4 : 1 for plasma membrane-colocalized EGFR–EGF that we can explain using novel time-dependent kinetics modelling, indicating preferential ligand binding to monomers. Our results may inform future cancer drug developments.

Inhibiting PP2Acα Promotes the Malignant Phenotype of Gastric Cancer Cells through the ATM/METTL3 Axis

This article is aimed at exploring the relationship between the phosphatase 2A catalytic subunit Cα (PP2Acα, encoded by PPP2CA) and methyltransferase-like 3 (METTL3) in the malignant progression of gastric cancer (GC). Through analyzing the bioinformatics database and clinical tissue immunohistochemistry results, we found that abnormal PP2Acα and METTL3 levels were closely related to the malignant progression of GC. To explore the internal connection between PP2Acα and METTL3 in the progression of GC, we carried out cellular and molecular experiments and finally proved that PP2Acα inhibition can upregulate METTL3 levels by activating ATM activity, thereby promoting the malignant progression of GC.

KK-LC-1 may be an effective prognostic biomarker for gastric cancer

Background

The objective of the study was to detect the expression of Kita-Kyushu lung cancer antigen-1 (KK-LC-1) in gastric cancer (GC) specimens and analyse the associations between KK-LC-1 expression and clinicopathological parameters and clinical prognosis.

Methods

All of the 94 patients in this study were GC patients who underwent surgical resection. KK-LC-1 protein expression in GC tissue was detected by immunohistochemistry. This report applies the histological score (H-score) to evaluate KK-LC-1 expression. To calculate this indicator, the number of positive cells in each section and their staining intensity were converted to corresponding values. The expression of KK-LC-1 in the cytoplasm of cancer and normal tissues was scored to obtain their respective H values. The chi-square test, Kaplan-Meier method and Cox regression were used to analyse the linear association between KK-LC-1 expression and clinicopathological data and prognosis.

Results

In the cytoplasm, KK-LC-1 expression in tumour tissues was significantly higher than that in normal tissues (P < 0.001). Using the median H-score as the cut-off value, we discovered that GC patients with high levels of KK-LC-1 expression in the cytoplasm had favourable overall survival (OS) (P = 0.016), and this result was statistically significant in the Cox regression analysis. Additionally, a negative correlation was found between KK-LC-1 protein expression and the pathological grade of the tumour (P = 0.036), with significantly more KK-LC-1 protein expression observed in the intestinal type of GC than in the diffuse type (P = 0.008).

Conclusions

Our research data showed that KK-LC-1 expression was greater in GC tissues than in normal tissues, and higher KK-LC-1 expression was associated with longer OS of GC patients. KK-LC-1 can be used as a biomarker for a good prognosis in GC patients.

Methylxanthine derivatives promote autophagy in gastric cancer cells targeting PTEN

Methylxanthine derivatives, such as caffeine and theophylline, enhance cell apoptosis and autophagy and reportedly induce the activity of phosphatase and tensin homologue (PTEN) and inhibit the mammalian target of rapamycin (mTOR). This study investigated the impacts of caffeine and theophylline on gastric cancer cell apoptosis and autophagy using a gastric cancer cell line (MGC-803) and a nude mouse model. Peritumoural and tumour tissues were collected from five patients diagnosed with gastric carcinoma who underwent laparoscopic radical gastrectomy at our hospital. Autophagy was suppressed in gastric cancer tumour tissue compared with peritumoural tissue. In vitro, both caffeine and theophylline effectively suppressed MGC-803 cell proliferation and migration and induced autophagy. To assess the involvement of PTEN in caffeine-mediated and theophylline-mediated gastric cancer cell death, we transiently transfected MGC-803 cells with an siRNA targeting PTEN. PTEN knockdown impaired the methylxanthine derivative-mediated inhibition of PI3K/Akt/mTOR signalling. In nude mice treated with caffeine or theophylline, MGC-803 cell tumours injected with siPTEN were larger than those injected with negative control siRNA. These results show that the methylxanthine derivatives (caffeine and theophylline) effectively induce gastric cancer cell apoptosis and autophagy by PTEN activation and PI3K/Akt/mTOR pathway suppression and strongly support the use of methylxanthine derivatives as potential anticancer therapeutics.

Mechanism Analysis of Coix Seed in Gastric Cancer Treatment Based on Biological Network Modules

Coix seed, the mature seed of Coix lacryma-jobi L., is a traditional herb widely used in various cancer adjuvant treatments; however, its mechanism is unknown. The aim of this study was to reveal the multitarget mechanisms of Coix seed in the treatment of gastric cancer (GC) by biological network and modular analysis methods. Forty-one ingredients and 482 targets of Coix seed and 165 GC-related genes were obtained from databases. Twelve on-target genes ( AICDA, CASP3, EP300, ERBB2, FGFR2, IL12A, IL12B, IL1B, LOX, TJP1, TP53, and TRIB3) of Coix seed overlapped with GC-related genes. Using compound-target and protein–protein interaction network analyses, we discovered the core targets of Coix seed. Markov cluster algorithm-based modular analysis identified 5 potential module targets of Coix seed for GC. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis demonstrated the vast actions of Coix seed, which involve pathways in cancer, the cell cycle, receptor signal transduction, deoxyribonucleic acid damage response, transcriptional regulation, apoptosis, and cell connections. This study elucidated the potential mechanisms of Coix seed on GC, which may lead to the development of an effective drug. Additionally, this study showed the feasibility of network and modular analysis methods to investigate traditional Chinese medicinal herbal mechanisms and may provide a new angle for further research in the field of anticancer mechanisms and multitarget drugs.

Nucleolin-Sle A Glycoforms as E-Selectin Ligands and Potentially Targetable Biomarkers at the Cell Surface of Gastric Cancer Cells

BACKGROUND

Gastric cancer (GC) is a major health burden worldwide, with half of patients developing metastases within 5 years after treatment, urging novel biomarkers for diagnosis and efficient therapeutic targeting. Sialyl-Lewis A (SLeA), a terminal glycoepitope of glycoproteins and glycolipids, offers tremendous potential towards this objective. It is rarely expressed in healthy tissues and blood cells, while it is present in highly metastatic cell lines and metastases. SLeA is also involved in E-selectin mediated metastasis, making it an ideal target to control disease dissemination.

METHODS AND RESULTS

To improve cancer specificity, we have explored the SLeA-glycoproteome of six GC cell models, with emphasis on glycoproteins showing affinity for E-selectin. A novel bioinformatics-assisted algorithm identified nucleolin (NCL), a nuclear protein, as a potential targetable biomarker potentially involved in metastasis. Several immunoassays, including Western blot and in situ proximity ligation reinforced the existence of cell surface NCL-SLeA glycoforms in GC. The NCL-SLeA glycophenotype was associated with decreased survival and was not reflected in relevant healthy tissues.

CONCLUSIONS

NCL-SLeA is a biomarker of poor prognosis in GC holding potential for precise cancer targeting. This is the first report describing SLeA in preferentially nuclear protein, setting a new paradigm for cancer biomarkers discovery and targeted therapies.

MicroRNA-128 contributes to the progression of gastric carcinoma through GAREM-mediated MAPK signaling activation

Gastric carcinoma (GC) represents the most common malignant cancer and the second leading cause of cancer death worldwide. However, the molecular mechanisms and biological progression of GC remain unknown. In this study, we found that miR-128 is a critical tumor suppressor that is downregulated in GC patients and GC cells and that GAREM is a direct downstream target of miR-128. Overexpression of miR-128 in HGC-27 and MKN-45 cells resulted in suppressed cell growth and promoted cell apoptosis through a GAREM-dependent mechanism. Moreover, the precise mechanisms underlying the antitumor effect of miR-128 in GC are at least partially due to suppressing activation of the MAPK signaling pathway, induced by suppressing GAREM expression. This study is the first to demonstrate that the miR-128-GAREM-MAPK signaling pathway forms a critical feedback loop and mediates GC development, and these findings might demonstrate a potential therapeutic strategy for GC.

Transcriptional repression of human epidermal growth factor receptor 2 by ClC-3 Cl- /H+ transporter inhibition in human breast cancer cells

Recent studies have indicated that the intracellular concentration of chloride ions (Cl⁻) regulates gene expression in several types of cells and that Cl⁻ modulators positively or negatively regulate the PI3K/AKT/mammalian target of rapamycin (mTOR) and signal transducer and activator of transcription (STAT)3 signaling pathways. We previously reported that the Ca²⁺‐activated Cl⁻ channel anoctamine (ANO)1 regulated human epidermal growth factor receptor 2 (HER2) transcription in breast cancer YMB‐1 cells. However, the mechanisms underlying ANO1‐regulated HER2 gene expression have not yet been elucidated. In the present study, we showed the involvement of intracellular organelle ClC‐3 Cl⁻/H⁺ transporter in HER2 transcription in breast cancer MDA‐MB‐453 cells. The siRNA‐mediated inhibition of ClC‐3, but not ANO1, markedly repressed HER2 transcription in MDA‐MB‐453 cells. Subsequently, treatments with the AKT inhibitor AZD 5363 and mTOR inhibitor everolimus significantly enhanced HER2 transcription in MDA‐MB‐453 cells, whereas that with the STAT3 inhibitor 5,15‐diphenylporphyrin (5,15‐DPP) inhibited it. AKT and mTOR inhibitors also significantly enhanced HER2 transcription in YMB‐1 cells. The siRNA‐mediated inhibition of ClC‐3 and ANO1 resulted in increased AKT phosphorylation and decreased STAT3 phosphorylation in MDA‐MB‐453 and YMB‐1 cells, respectively. The intracellular Cl⁻ channel protein CLIC1 was expressed in both cells; however, its siRNA‐mediated inhibition did not elicit the transcriptional repression of HER2. Collectively, our results demonstrate that intracellular Cl⁻ regulation by ANO1/ClC‐3 participates in HER2 transcription, mediating the PI3K/AKT/mTOR and/or STAT3 signaling pathway(s) in HER2‐positive breast cancer cells, and support the potential of ANO1/ClC‐3 blockers as therapeutic options for patients with resistance to anti‐HER2 therapies.

Optimizing miRNA-module diagnostic biomarkers of gastric carcinoma via integrated network analysis

Several microRNAs (miRNAs) have been suggested as novel biomarkers for diagnosing gastric cancer (GC) at an early stage, but the single-marker strategy may ignore the co-regulatory relationships and lead to low diagnostic specificity. Thus, multi-target modular diagnostic biomarkers are urgently needed. In this study, a Z_summary and NetSVM-based method was used to identify GC-related hub miRNAs and activated modules from clinical miRNA co-expression networks. The NetSVM-based sub-network consisting of the top 20 hub miRNAs reached a high sensitivity and specificity of 0.94 and 0.82. The Z_summary algorithm identified an activated module (miR-486, miR-451, miR-185, and miR-600) which might serve as diagnostic biomarker of GC. Three members of this module were previously suggested as biomarkers of GC and its 24 target genes were significantly enriched in pathways directly related to cancer. The weighted diagnostic ROC AUC of this module was 0.838, and an optimized module unit (miR-451 and miR-185) obtained a higher value of 0.904, both of which were higher than that of individual miRNAs. These hub miRNAs and module have the potential to become robust biomarkers for early diagnosis of GC with further validations. Moreover, such modular analysis may offer valuable insights into multi-target approaches to cancer diagnosis and treatment.

The bile acid receptor GPBAR1 (TGR5) is expressed in human gastric cancers and promotes epithelial-mesenchymal transition in gastric cancer cell lines

GPBAR1 (also known as TGR5) is a bile acid activated receptor expressed in several adenocarcinomas and its activation by secondary bile acids increases intestinal cell proliferation. Here, we have examined the expression of GPBAR1 in human gastric adenocarcinomas and investigated whether its activation promotes the acquisition of a pro-metastatic phenotype. By immunohistochemistry and RT-PCR analysis we found that expression of GPBAR1 associates with advanced gastric cancers (Stage III-IV). GPBAR1 expression in tumors correlates with the expression of N-cadherin, a markers of epithelial-mesenchymal transition (EMT) (r=0.52; P<0.01). Expression of GPBAR1, mRNA and protein, was detected in cancer cell lines, with MKN 45 having the higher expression. Exposure of MKN45 cells to GPBAR1 ligands, TLCA, oleanolic acid or 6-ECDCA (a dual FXR and GPBAR1 ligand) increased the expression of genes associated with EMT including KDKN2A, HRAS, IGB3, MMP10 and MMP13 and downregulated the expression of CD44 and FAT1 (P<0.01 versus control cells). GPBAR1 activation in MKN45 cells associated with EGF-R and ERK1 phosphorylation. These effects were inhibited by DFN406, a GPBAR1 antagonist, and cetuximab. GPBAR1 ligands increase MKN45 migration, adhesion to peritoneum and wound healing. Pretreating MKN45 cells with TLCA increased propensity toward peritoneal dissemination in vivo. These effects were abrogated by cetuximab. In summary, we report that GPBAR1 is expressed in advanced gastric cancers and its expression correlates with markers of EMT. GPBAR1 activation in MKN45 cells promotes EMT. These data suggest that GPBAR1 antagonist might have utility in the treatment of gastric cancers.

MicroRNA-34a regulates proliferation and apoptosis of gastric cancer cells by targeting silent information regulator 1

The present study aimed to identify whether microRNA (miRNA/miR)-34a regulates the proliferation and apoptosis of gastric cancer cells by targeting silent information regulator 1 (SIRT1). The expression of miR-34a and SIRT1 and cell viability was investigated in gastric cancer cells. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was applied to determine miR-34a expression in gastric adenocarcinoma, normal pericarcinomatous tissues, human normal gastric mucosa epithelial cell line GES and various gastric cancer cell strains. A bioinformatics method was then used to predict the target gene of miR-34a. A human miR-34a over expression lentiviral vector system was constructed and then used for transfection of the gastric cancer cell line SCG-7901 to determine the expression of SIRT1 mRNA and SIRT1 protein using RT-qPCR and western blot analysis. The MTT method and flow cytometry was used to measure cell proliferation and apoptosis. The relative expression of miR-34a in gastric cancer tissues was significantly decreased compared with that in normal tissues (P<0.01). miR-34a expression was also significantly decreased in low differentiated N2, N3 gastric cancer tissues (P<0.01). However, tumor size and filtration degree were not significantly associated with miR-34a expression. The relative expression of miR-34a was decreased in gastric cancer cells, especially in the SGC-7901 cell line (P<0.01) compared with the GES group. The relative expression of SIRT1 protein was decreased in the miR-34a group compared with the negative control (P<0.01). The rate of proliferation was significantly decreased, whereas the rate of apoptosis was significantly increased in the miR-34a group compared with the NC group (P<0.01). Therefore, the present results suggested that miRNA-34a serves a pivotal role in gastric cancer as a cancer suppressor gene by targeting SIRT1 to regulate the proliferation and apoptosis of gastric cancer cells.

Efficacy and safety of targeting VEGFR drugs in treatment for advanced or metastatic gastric cancer: a systemic review and meta-analysis

The value of targeting VEGFR (vascular endothelial growth factor receptor) drugs has demonstrated encouraging anti-cancer activity in advanced solid tumors within current clinical trials. This study aimed to serve as the first systemic review to assess their safety and efficacy according to biochemical characteristics of targeting VEGFR drugs in gastric cancer. We analyzed eight clinical trials on targeting VEGFR drugs in gastric cancer. Results showed that targeting VEGFR drugs significantly improved overall survival (OS) [Hazard Ratio (HR) 0.69, 95% confidence interval (CI) (0.55, 0.83), P < 0.001], progression free survival (PFS) [HR 0.50, 95% CI (0.34, 0.66), P < 0.001], disease control rate (DCR) [Odds Ratio (OR) 3.83, 95% CI (2.39, 6.15), P < 0.001] and significantly decreased the progressive disease rate(PDR)[OR 0.45, 95% CI (0.34, 0.59), P < 0.001], but not objective response rate (ORR) [OR 1.46, 95% CI (0.93, 2.29), P = 0.098]. Further subgroup revealed that VEGFR antibody (VEGFR-Ab) drugs were superior to VEGFR tyrosine kinase inhibitor (VEGFR-TKI) drugs in terms of the OS, PFS and PDR. To determine the toxic effect of targeting VEGFR drugs, the relative risk of adverse events (grade ≥ 3) of special interest(AESIs) were estimated. Most of these were predictable and manageable. Furthermore, less AESIs were observed in the VEGFR-Ab than the VEGFR-TKI drugs. In conclusion, VEGFR drugs were effective targeted therapy in advanced or metastatic gastric cancer, and its toxicity is within a controllable range. VEGFR-Ab drugs were more effective than VEGFR-TKI drugs in terms of the OS, PFS and PDR of gastric cancer patients with little toxicity.

Treatment-related severe and fatal adverse events with molecular targeted agents in the treatment of advanced gastric cancer: a meta-analysis

AIM

To perform a systematic review and meta-analysis of Phase III randomized controlled trials (RCTs) to determine the incidence and risk of severe adverse events (AEs) with molecular targeted agents (MTAs) in advanced/metastatic gastric cancer (GC) patients.

METHODS

A comprehensive literature search for related trials published up to December 2015 was performed. Eligible studies were Phase III RCTs of advanced/metastatic GC patients assigned to MTAs or control group. Data were extracted by two authors for severe and fatal AEs (FAEs).

RESULTS

A total of nine Phase III RCTs involved 4,934 GC patients were ultimately identified. The pooled results demonstrated that the addition of TAs to therapies in advanced GC significantly increased the risk of developing severe AEs (relative risk: 1.12, 95% confidence interval: 1.02-1.24, P=0.02), but not for FAEs (relative risk: 0.97, 95% confidence interval: 0.65-1.45, P=0.88). Additionally, the most common causes of FAEs with MTAs were infections (16.3%), gastrointestinal hemorrhage (8.2%), and arterial thromboembolic events (8.2%), respectively.

CONCLUSION

With available evidence, the use of TAs in GC patients was associated with an increased risk of severe AEs, but not for FAE. Clinicians should be aware of the risk of severe AEs with the administration of these drugs in these patients.

The role of antiangiogenic agents in the treatment of gastric cancer: A systematic review and meta-analysis

BACKGROUND

The survival of advanced gastric cancer (GC) is dismal, and effects of antiangiogenic agents remain inconclusive. The purpose of this study is to assess combination of chemotherapy with antiangiogenic therapy versus traditional chemotherapy.

METHODS

To achieve the goal of scientific rigor, statistics from both referenced works and experiments were analyzed. We carefully searched for the referenced works by retrieving, as well as analyzing, literature databases for information on antiangiogenic therapy compared to other therapeutic approaches used to treat GC patients. Two groups were defined in the experiment: experimental and control groups. The experimental group was treated with antiangiogenic drug, and the control group was treated with standard chemotherapy or placebo.

RESULTS

The study included a total of 3240 participants. Overall, there was significant improvement in overall survival (hazard ratio [HR] = 0.78, 95% confidence interval [CI]: 0.67-0.91, P = 0.002), progression-free survival (HR 0.65, 95% CI: 0.52-0.81, P = 0.0002), objective response rate (risk ratio [RR] = 1.58, 95% CI: 1.33-1.88, P < 0.00001), and disease control rate (RR 2.44, 95% CI: 1.57-3.78, P < 0.0001) in the group with antiangiogenic drug versus the group with standard chemotherapy or placebo. Moreover, this new treatment approach showed tolerable toxicity.

CONCLUSION

This study confirms the superior efficacy of combination therapy with antiangiogenic agents in comparison to traditional chemotherapy regimens for patients with GC. Moreover, this new treatment approach showed tolerable toxicity. This meta-analysis provides important information for clinicians who are interested in using antiangiogenic therapies to treat GC patients.

Oncolytic Adenovirus Expressing Monoclonal Antibody Trastuzumab for Treatment of HER2-Positive Cancer

Monoclonal anti-HER2 antibody trastuzumab has significantly improved the survival of patients with HER2-overexpressing tumors. Nevertheless, systemic antibody therapy is expensive, limited in efficacy due to physical tumor barriers, and carries the risk of severe side effects such as cardiomyopathy. Oncolytic viruses mediate cancer-selective transgene expression, kill infected cancer cells while mounting antitumor immune responses, and have recently demonstrated promising efficacy in combination treatments. Here, we armed an oncolytic adenovirus with full-length trastuzumab to achieve effective in situ antibody production coupled with progressive oncolytic cancer cell killing. We constructed an infectivity-enhanced serotype 5 oncolytic adenovirus, Ad5/3-Δ24-tras, coding for human trastuzumab antibody heavy- and light-chain genes, connected by an internal ribosome entry site. Infected cancer cells were able to assemble full-length functional antibody, as confirmed by Western blot, ELISA, and antibody-dependent cell-mediated cytotoxicity assay. Importantly, oncolysis was required for release of the antibody into tumors, providing additional spatial selectivity. Ad5/3-Δ24-tras showed potent in vitro cytotoxicity and enhanced antitumor efficacy over oncolytic control virus Ad5/3-Δ24 or commercial trastuzumab in HER2-positive cancer models in vivo (both P < 0.05). Furthermore, Ad5/3-Δ24-tras resulted in significantly higher tumor-to-systemic antibody concentrations (P < 0.001) over conventional delivery. Immunological analyses revealed dendritic cell activation and natural killer cell accumulation in tumor-draining lymph nodes. Thus, Ad5/3-Δ24-tras is an attractive anticancer approach combining oncolytic immunotherapy with local trastuzumab production, resulting in improved in vivo efficacy and immune cell activation in HER2-positive cancer. Moreover, the finding that tumor cells can produce functional antibody as directed by oncolytic virus could lead to many valuable antitumor approaches. Mol Cancer Ther; 15(9); 2259-69. ©2016 AACR.

Exploring the role of molecular biomarkers as a potential weapon against gastric cancer: A review of the literature

Gastric cancer (GC) is a global health problem and a major cause of cancer-related death with high recurrence rates ranging from 25% to 40% for GC patients staging II-IV. Unfortunately, while the majority of GC patients usually present with advanced tumor stage; there is still limited evidence-based therapeutic options. Current approach to GC management consists mainly of; endoscopy followed by, gastrectomy and chemotherapy or chemo-radiotherapy. Recent studies in GC have confirmed that it is a heterogeneous disease. Many molecular characterization studies have been performed in GC. Recent discoveries of the molecular pathways underlying the disease have opened the door to more personalized treatment and better predictable outcome. The identification of molecular markers is a useful tool for clinical managementin GC patients, assisting in diagnosis, evaluation of response to treatment and development of novel therapeutic modalities. While chemotherapeutic agents have certain physiological effects on the tumor cells, the prediction of the response is different from one type of tumor to the other. The specificity of molecular biomarkers is a principal feature driving their application in anticancer therapies. Here we are trying to focus on the role of molecular pathways of GC and well-established molecular markers that can guide the therapeutic management.

Inhibitory effects of bevacizumab monoclonal antibodies in combination with chemotherapy in different time sequences on a human gastric carcinoma cell line

OBJECTIVE

This study investigated the inhibitory effects of bevacizumab monoclonal antibodies in combination with chemotherapy in different time sequences on a human gastric cancer cell line (MGC-803).

METHODS

Cultured MGC-803 human gastric cancer cells were treated with bevacizumab in combination with chemotherapy treatment in different time sequences. The effects on cell growth inhibition were determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Cell cycle distribution and the rate of cell apoptosis were determined by propidium iodide staining followed by flow cytometry.

RESULTS

Drug administration for different time sequences significantly inhibited the growth of MGC-803 cells. Based on group comparisons (P < 0.01), the effect of 24 h bevacizumab treatment prior to combination 5-fluorouracil and cisplatin (FP) was the strongest (F = 241.313, 246.856, all P values <0.001). Treating MGC-803 cells with bevacizumab for 24 h before combination FP induced significant G2/M phase arrest (F = 231.991, P < 0.001) and significantly increased gastric cancer cell apoptosis. Bevacizumab in combination with chemotherapy significantly inhibits the proliferation of MGC-803 gastric cancer cells.

CONCLUSIONS

The mechanism may be related to cell cycle arrest at S phase and the induction of apoptosis in MGC-803 gastric cancer cells.

Screening Driving Transcription Factors in the Processing of Gastric Cancer

Background. Construction of the transcriptional regulatory network can provide additional clues on the regulatory mechanisms and therapeutic applications in gastric cancer. Methods. Gene expression profiles of gastric cancer were downloaded from GEO database for integrated analysis. All of DEGs were analyzed by GO enrichment and KEGG pathway enrichment. Transcription factors were further identified and then a global transcriptional regulatory network was constructed. Results. By integrated analysis of the six eligible datasets (340 cases and 43 controls), a bunch of 2327 DEGs were identified, including 2100 upregulated and 227 downregulated DEGs. Functional enrichment analysis of DEGs showed that digestion was a significantly enriched GO term for biological process. Moreover, there were two important enriched KEGG pathways: cell cycle and homologous recombination. Furthermore, a total of 70 differentially expressed TFs were identified and the transcriptional regulatory network was constructed, which consisted of 566 TF-target interactions. The top ten TFs regulating most downstream target genes were BRCA1, ARID3A, EHF, SOX10, ZNF263, FOXL1, FEV, GATA3, FOXC1, and FOXD1. Most of them were involved in the carcinogenesis of gastric cancer. Conclusion. The transcriptional regulatory network can help researchers to further clarify the underlying regulatory mechanisms of gastric cancer tumorigenesis.

The combinational therapy of trastuzumab and cetuximab inhibits tumor growth in a patient-derived tumor xenograft model of gastric cancer

PURPOSE

Gastric cancer (GC) is one of the leading causes of cancer mortality worldwide. Although therapeutic strategies for GC have improved, the prognosis for advanced GC remains poor. Herein, the present study sought to design a personalized cancer therapy specific to a stage III GC patient.

METHODS

The tumor was surgically removed and was used to establish a patient-derived tumor xenograft (PDTX) model utilizing nude mice. Various molecular-targeted anticancer treatments were tested in the study, including control (no treatment), bevacizumab, cetuximab, bevacizumab + cetuximab, trastuzumab, and trastuzumab + cetuximab.

RESULTS

Trastuzumab + cetuximab treatment exhibited the best antitumor growth effect, followed by trastuzumab, bevacizumab + cetuximab, cetuximab, and bevacizumab. Similarly, trastuzumab + cetuximab was also the most effective treatment at inducing apoptosis and cell cycle arrest in primary cultures of the patient's gastric cancer cells. Among all treatments tested in the study, trastuzumab + cetuximab showed the most profound effect in reducing the protein expression of proliferation and metastatic markers (VEGF, MMP-7, EGFT, Ki-67 and, PCNA) in tumors obtained from PDTX models, which may be the mechanism underlying the profound antitumor growth effect exerted by trastuzumab + cetuximab.

CONCLUSIONS

The data indicate that trastuzumab + cetuximab combinational therapy should be the most effective antitumor growth therapy for the GC patient whom we took the cancer cells from.

CecropinXJ inhibits the proliferation of human gastric cancer BGC823 cells and induces cell death in vitro and in vivo

We have shown that an antimicrobial peptide (AMP) cecropinXJ isolated from the larvae of Bombyx mori selectively inhibits the proliferation of cancer cells. However, the mechanism remains to be determined. In the present study, we examined the antitumor activity of cecropinXJ against human gastric cancer BGC823 cells and explored the mechanism. The results showed that cecropinXJ inhibited the growth of gastric cancer BGC823 cells in vitro and in vivo. MTT and colony formation assays indicated that cecropinXJ suppressed cell proliferation and reduced colony formation of BGC823 cells in a dose- and time-dependent manner, but without inhibitory effect on normal gastric epithelia GES-1 cells. S-phase arrest in BGC823 cells was observed after treatment with cecropinXJ. Annexin V/PI staining suggested that cecropinXJ induced both early and late phases of apoptosis through activation of mitochondrial-mediated caspase pathway, upregulation of Bax expression and downregulation of Bcl-2 expression. Additionally, cecropinXJ treatment increased reactive oxygen species (ROS) production, disrupted the mitochondrial membrane potential (Δψm) and led to release of cytochrome c. Importantly, in vivo study showed that cecropinXJ significantly prevented the growth of xenograft tumor in the BGC823-bearing mice, possibly mediated by the induction of apoptosis and inhibition of angiogenesis. These results suggest that cecropinXJ may be a promising therapeutic candidate for the treatment of gastric cancer.