Beneficial Effects of Gracillin From Rhizoma Paridis Against Gastric Carcinoma via the Potential TIPE2-Mediated Induction of Endogenous Apoptosis and Inhibition of Migration in BGC823 Cells

Tumor necrosis factor-α inducible protein-8 (TIPE2), initially recognized as a negative immune regulator, exerts an important role in suppressing the progression of numerous cancers. In our previous investigation, we found that TIPE2 expression displayed a decrease or absence in gastric tumor tissue, and the overexpression of TIPE2 suppressed the growth of gastric cancer tumors and cells, demonstrating that TIPE2 could be a potential medicinal target for gastric cancer treatment. However, it’s seldomly reported that several medicinal agents or candidates targeted TIPE2 for treating diseases, including gastric cancer. To identify the candidate targeting TIPE2 to fight against gastric cancer, several extractions from traditional natural medicinal plants with anti-tumor functions were employed to screen the active compounds according to bioassay-guided isolation. Interestingly, gracillin, a component from the ethyl acetate extraction of Rhizoma Paridis, was identified to induce the expression of TIPE2 and inhibit the cell proliferation in gastric cancer BGC-823 cells. Furthermore, the underlying mechanisms that restrain gastric cancer were evaluated by clone formation, EdU staining, flow cytometry, and other assays. Meanwhile, the role of TIPE2 in the anti-tumor effect of gracillin was elucidated via the use of siTIPE2 RNA. It was determined that gracillin could fight against gastric cancer cells by inhibiting the cell proliferation participated by the PI3K/AKT pathway and cell cycle arrest, suppressing the EMT pathway-regulating cell migration, and inducing bcl2-associated mitochondrial apoptosis. Additionally, TIPE2 maybe contribute to the benefits of gracillin. These results of the present study are an important step toward the medicinal development of gracillin, and are also of use in understanding the effect of TIPE2 as a potential tumor target.

Claudin-6 is down-regulated in gastric cancer and its potential pathway

Claudins are indispensible in modulating the permeability of epithelial and endothelial cells and in the maintenance of cell polarity. In order to verify the function of claudin-6 in the development of gastric cancer, we investigated claudin-6 expression in different gastric disease tissues. Moreover, we further explored whether overexpression of claudin-6 altered proliferation, apoptosis, migration, invasiveness, differentiation in BGC-823 cells and the potential mechanism. Immunohistochemistry was performed to detect the in situ expression of claudin-6 in different gastric disease tissues; moreover, cell culture, real-time PCR and western blot were used to evaluate the effect of overexpression of claudin-6 in vitro and the related mechanism. The results of immunohistochemical staining showed that the positivity of claudin-6 was significantly higher in superficial gastritis than that in gastric cancer. Overexpression of claudin-6 induced differentiation of BGC-823 cells by inhibiting the JNK pathway. However, it had no effect on proliferation, apoptosis, migration or invasiveness in vitro. The expression of claudin-6 was decreased in gastric cancer. Overexpression of claudin-6 induced differentiation of gastric cancer cells by inhibiting the JNK pathway.

MiR-135b-5p promotes viability, proliferation, migration and invasion of gastric cancer cells by targeting Krüppel-like factor 4 (KLF4)

INTRODUCTION

The expression of MiR-135b-5p was up-regulated while Krüppel-like factor 4 (KLF4) expression was extremely low in human gastric carcinoma (GC) tissues. This study aimed to explore the role of miR-135b-5p in GC cells and its influence on various cell capacity and viability by targeting KLF4.

MATERIAL AND METHODS

The dual-luciferase reporter assay was first performed and the target relationship between miR-135b-5p and KLF4 was confirmed. Then three GC cell lines and the human normal gastric epithelial cell line (GES1) were analyzed for the expression level of miR-135b-5p and KLF4 mRNA by RT-qPCR. The BGC-823 GC cell line was chosen for subsequent assays.

RESULTS

The expression of miR-135b-5p and KLF4 was manipulated via transfection. The changes of proliferation, invasion, migration, viability, cycle and apoptosis of GC cells were evaluated by MTS, colony formation assay, transwell assay, wound healing assay and flow cytometry assay, respectively. Overexpression of MiR-135b-5p enhanced viability, proliferation, invasion and migration of GC cells, increased cell viability and reduced cell apoptosis. Replenishing of KLF4 functioned oppositely.

CONCLUSIONS

The inhibitory effects of ectopic KLF4 could be attenuated by co-transfection of miR-135b-5p. Collective data suggested that miR-135b-5p has a tumor-promoting role in GC cells via downregulating KLF4. Hence, inhibition of miR-135b-5p could be valuable for treatment of gastric cancer.

VEGFR-2 Inhibitor Apatinib Hinders Endothelial Cells Progression Triggered by Irradiated Gastric Cancer Cells-derived Exosomes

Background: Radiotherapy is a standard treatment for a significant fraction of cancer patients. Nonetheless, to this day radiation resistance is a key impediment in gastric cancer (GC) treatment. Moreover, GC is characterized by its substantial neo-angiogenesis, driven by high levels of vascular endothelial growth factor (VEGF) correlated with the presence of stomach cancer. The aim of our study was to address if VEGFR inhibitors treatments impact the negative effect of radiotherapy regiments of gastric cancer.

Materials and methods: Isolation of exosomes released by SGC-7901 and BGC-823 lines after irradiation at 0 Gy or 6 Gy was performed by differential ultra-centrifugation. Incubation of Human Umbilical Vein Endothelial Cells (HUVEC) was carried out with different concentrations of exosomes from non- or irradiated GC cells to address their proliferation and survival fraction (SF) by MTS. 6 Gy irradiated cells exosomes at concentration of 20 µg/ml were compared to EC incubated with the same exosome concentration from non-irradiated human GC cells over 72-hour time course. Wound-healing and Transwell assays were performed in a migration buffer consisting of exosomes released by non- or irradiated SGC-7901 and BGC-823 cells over 24-hour time course. HUVEC cells stained with DAPI that have passed through a gluten gel were counted in order to monitor their invasion capacity. Employing IC50, 60 µg/ml was determined as the optimal Apatinib (YN968D1) concentration for the half-life of HUVEC, and incubated with exosomes from irradiated GC cells. The aforementioned assays were performed in the background of the same conditions in order to analyse the effect of Apatinib on HUVEC progression.

Results: We show that proliferation, motility and invasive capacity of HUVEC are enhanced upon incubation with exosomes released by irradiated GC cell lines. Importantly, the latter is counteracted by the VEGFR-2 inhibitor Apatinib which hinders ECs progression.

Conclusion / Significance: Combining radiotherapy and VEGFR inhibitors treatment can provide potentially a substantial impact in decreasing cancer death rates by averting the negative effect of radiotherapy regiments and provide better standard for cancer patients.

Association between CXCR2 and IL-22BP expression indicate a poor outcome for gastric adenocarcinoma progression

C-X-C motif chemokine receptor type 2 (CXCR2), a key regulatory protein, has been associated with multiple roles in the progression of numerous tumors, including gastric adenocarcinoma (GA). However, the mechanism of CXCR2 in the development of tumors remains controversial and unclear. In a previous study, the expression of CXCR2 and interleukin-22 receptor 2 (IL-22BP) was observed in GA. This promoted the present study, which aimed to explore the association between the two proteins, and to further analyze their roles in GA. CXCR2 and IL-22BP protein expression was analyzed by immunohistochemistry and reverse transcription-quantitative polymerase chain reaction assays in gastric cancer (GC) tissue, additionally confirmed via western blotting and immunocytochemical analysis in the MKN-45, BGC-823 and SGC-7901 cell lines. The association between expression levels and clinicopathological characteristics was evaluated by the Mann-Whitney U and Kruskal-Wallis tests. Using Kaplan-Meier plots and Cox proportional hazard models, overall survival (OS) was analyzed. Compared with non-cancerous tissue, CXCR2 and IL-22BP were over expressed (P<0.001 and P<0.001, respectively), and were observed mainly in the cytoplasm (P=0.022 and P=0.014, respectively) in GA. The associated protein and messenger RNA levels were analyzed, and coexpression was identified. Increased expression and more positive cases of CXCR2 and IL-22BP were observed with advanced pathological tumor-node-metastasis (p-TNM) stage in GC (P<0.001 and P<0.001, respectively), as well as the presence and absence of lymph node metastasis (LNM) (P=0.003 and P=0.041, respectively) and deep or superficial muscular invasion (P=0.002 and P=0.004, respectively). In addition, an association between IL-22BP and tumor diameter was indicated (P=0.021). In a Kaplan-Meier analysis, compared with negative expression, the two proteins identified a group of patients with the shortest OS. Cox proportional hazard models revealed that the two proteins, in addition to p-TNM stage, LNM and depth of invasion, predicted a short time to OS. The coexpression of CXCR2 and IL-22BP was demonstrated in GA, which may indicate that CXCR2 is involved in more complex mechanisms and roles, and indicate a poor outcome in GA progression.

The saponin DT-13 inhibits gastric cancer cell migration through down-regulation of CCR5-CCL5 axis

AIM

To investigate the effect of DT-13 on gastric cancer cell migration, and to explore the possible mechanisms underlying the anti-metastasis activity of DT-13.

METHODS

Growth inhibition of DT-13 was analyzed by the MTT assay. Cell migration was measured by the scratch-wound assay and transwell double chamber assay. To investigate the possible mechanisms underlying the anti-metastasis activity of DT-13, chemokine receptors that are involved in cancer metastasis (CCR2, CCR5, CCR7, CXCR4, and CXCR6) were detected by conventional PCR. The effect of DT-13 on CCR5 and CXCR4 expression was further evaluated by quantitative PCR and Western blot, respectively. The secretion of CCL5 (ligand of CCR5) and SDF-1 (ligand of CXCR4) were detected by enzyme-linked immunosorbent assay (ELISA).

RESULTS

DT-13 inhibited BGC-823 and HGC-27 cell growth in a dose dependent manner, and the estimated IC50 value for 24 h treatment was 23.5 ± 5.1 μmol·L(-1) for BGC-823 cells and 35.6 ± 7.6 μmol·L(-1) for HGC-27 cells. DT-13 also significantly decreased gastric cancer cell migration. DT-13 significantly decreased the gene expression of CCR5 in both BGC-823 and HGC-27 gastric cancer cells, and moderately reduced the expression of CXCR4. Similar to the results of gene expression, significant down-regulation of CCR5 protein was observed, but CXCR4 protein levels were much less affected. CCL5 secretion, but not SDF-1 production, was inhibited by DT-13.

CONCLUSION

DT-13 inhibited gastric cancer cell migration by down-regulation of the CCR5-CCL5 axis.

Downregulation of growth differentiation factor-15 in trichostatin A-induced apoptosis could play a role in progression of gastric cancer

AIM

To investigate the effect of trichostatin A (TSA) on gastric cancer cell line BGC-823, and identify the differentially expressed genes induced by TSA, which might participate in the progression of gastric cancer.

METHODS

MTT, fluorescence microscopy, and flow cytometry were used to detect the effect of TSA on growth inhibition and apoptosis of BGC-823 cells. Using gene microarray, we analyzed the changes in gene expression. Change in growth differentiation factor-15 (GDF-15) was verified by qRT-PCR and Western blotting. The expression of GDF-15 in gastric cancer and adjacent normal tissues was detected by immunohistochemistry.

RESULTS

Apoptosis of BGC-823 cells induced by TSA (75 ng/mL for 48 h) was demonstrated by flow cytometry. There were significant variations between TSA treated groups and control groups (P = 0.02). Nuclear chromatin condensation and fluorescence intensity were observed by fluorescence microscopy. GDF-15 gene expression and protein level were significantly reduced in the TSA treated group (75 ng/mL for 48 h). Immunohistochemistry demonstrated that the expression of GDF-15 in gastric adenocarcinoma was significantly higher than in the surrounding normal tissues (P < 0.05).

CONCLUSION

Lower GDF-15 gene expression due to TSA-induced apoptosis was found in gastric cancer cell line BGC-823. Higher GDF-15 gene expression was seen in gastric adenocarcinoma tissues.

Differential expression of glycoprotein non-metastatic melanoma protein B (GPNMB) involved in trichostatin A-induced apoptosis in gastric cancer

In this study, we investigated the effect of trichostatin A (TSA) on the gastric cancer cell line BGC-823. The effect of TSA on growth inhibition and apoptosis of BGC-823 cells was examined. The gene expression profile was determined by microarray. Western blotting was used to study the levels of acetylated histone H4 and Glycoprotein non-metastatic melanoma protein B (GPNMB) proteins. GPNMB gene expression was measured by real-time PCR. GPNMB protein levels in gastric adenocarcinoma tissues and adjoining normal tissues were detected by immunohistochemistry. The results showed that a significant decrease in cell population following treatment with 75 ng/mL TSA for 48 h (0.87 ± 0.04) as compared to control (1.14 ± 0.06) (P = 0.02). Apoptotic cells were increased in TSA (75 ng/mL for 48 h) treated group as compared to the control group (from 2.02% to 19.74%) by flow cytometry. The expression of acetylated histone H4 was increased in TSA treated (75 ng/mL for 48 h) group (from 1.00 ± 0.26 to 1.87 ± 0.33, F = 5.862, P = 0.0038) as compared to the control group by Western blotting. After 48 h TSA treatment (75 ng/mL), BGC-823 cells showed decrease in GPNMB gene expression (from 1.00 ± 0.21 to 0.59 ± 0.11, F = 6.214, P = 0.0018). Immunohistochemistry showed that GPNMB expression in gastric adenocarcinoma was significantly higher than the adjoining normal tissues (P = 0.000). To conclusion, our results support that TSA can induce apoptosis, and increase acetylated histone H4 in BGC-823 cells. GPNMB expression is decreased in BGC-823 cells after TSA treatment. GPNMB is overexpressed in gastric adenocarcinoma tissue. GPNMB involved in TSA-induced apoptosis might participate in gastric cancer.

DHA combined with norcantharidin inhibits cell growth and promotes apoptosis in human gastric cancer cell line BGC-823

AIM: To investigate the synergistic effect of docosahexaenoic acid (DHA) and norcantharidin on cell growth and apoptosis in human gastric cancer cell line BGC-823 in vitro.

METHODS: BGC-823 cells were stained with NADH enzyme and acridine orange to observe their morphology under a microscope before and after treatment with DHA and norcantharidin. MTT assay and flow cytometry were used to measure cell proliferation and apoptosis, respectively.

RESULTS: Treatment with DHA and norcantharidin significantly reduced BGC-823 cell survival. After NADH enzyme and acridine orange staining, apoptotic cells were visible. Bcl-2 protein expression was significantly decreased. The percentage of cells at G₂/M phase and S phase was significantly decreased, whereas that of cells at G₀/G₁ phase was increased.

CONCLUSION: Treatment with DHA and norcantharidin synergistically inhibits cell proliferation and promotes apoptosis in human gastric cancer cell line BGC-823.

SN-38-loaded polymeric micelles can inhibit the growth of human gastric adenocarcinoma BGC-823 cells

AIM: To investigate the characteristics of SN-38-loaded polymeric micelles and compare their inhibitory effect on human gastric adenocarcinoma BGC-823 cells with that of free SN-38.

METHODS: SN-38/PCL-PEG nanoparticles (SN-38-NP) were synthesized by solvent diffusion method. The morphology of nanoparticles were detected by atomic force microscopy and transmission electron microscopy. The drug loading content, encapsulation efficiency, and in vitro release of SN-38-NP were evaluated by ultraviolet spectrophotometry and high-performance liquid chromatography (HPLC). The effects of SN-38-NP on the proliferation of BGC-823 cells were examined by methyl thiazolyl tetrazolium (MTT) assay. The level of reactive oxygen species (ROS) was detected by dichlorofluorescein (DCF) assay.

RESULTS: The average diameter of drug-loaded nanoparticles was less than 100 nm. The drug-loaded nanoparticles had higher drug loading content (about 11%) and encapsulation efficiency (about 80%) than free SN-38. SN-38 could be effectively incorporated into nanoparticles with core-shell structure to act as a water-soluble controlled release drug delivery system. The results of MTT assay showed that the half maximal inhibitory concentration (IC₅₀) of SN-38-NP was obviously lower than that of free SN-38 at 24 and 72 h after treatment (P < 0.05) though there was no significant difference at 48 h. Although both free SN-38 and SN-38 nanoparticles could increase ROS production, the SN-38-NP induced more ROS at low concentrations (P < 0.05).

CONCLUSION: SN-38-NP could be effectively incorporated into core-shell nanoparticles to act as a water-soluble controlled release drug delivery system. SN-38-NP is superior to free SN-38 in restraining the growth of tumor cells even at low concentrations.

Gastric cancer cell lines induced by trichostatin A

AIM: To explore the effect of trichostatin A (TSA) on apoptosis and acetylated histone H3 levels in gastric cancer cell lines BGC-823 and SGC-7901.

METHODS: The effect of TSA on growth inhibition and apoptosis was examined by MTT, fluorescence microscopy and PI single-labeled flow cytometry. The acetylated histone H3 level was detected by Western blot.

RESULTS: TSA induced apoptosis in gastric cancer cell lines BGC-823 and SGC-7901 was in a dose and time-dependent manner. Apoptotic cells varied significantly between TSA treated groups (37.5 ng/mL 72 h for BGC-823 cell line and 75 ng/mL 72 h for SGC-7901 cell line) and control group (0.85 ± 0.14 vs 1.14 ± 0.07, P = 0.02; 0.94 ± 0.07 vs 1.15 ± 0.06, P = 0.02). Morphologic changes of apoptosis, including nuclear chromatin condensation and fluorescence strength, were observed under fluorescence microscopy. TSA treatment in BGC-823 and SGC-7901 cell lines obviously induced cell apoptosis, which was demonstrated by the increased percentage of sub-G1 phase cells, the reduction of G1-phase cells and the increase of apoptosis rates in flow cytometric analysis. The result of Western blot showed that the expression of acetylated histone H3 increased in BGC-823 and SGC-7901 TSA treatment groups as compared with the control group.

CONCLUSION: TSA can induce cell apoptosis in BGC-823 and SGC-7901 cell lines. The expression of acetylated histone H3 might be correlated with apoptosis.

Inhibition of Allicin on G2/M phase of human gastric cell line SGC-7901 and BGC-823

AIM: To explore the inhibitory effect of Allicin on the G₂/M phase of human gastric cell line SGC-7901 and BGC-823 and its mechanism.

METHODS: The proliferation inhibition rate and IC₅₀ of Allicin (72 h) to SGC-7901 and BGC-823 cells were examined by MTT assay. The cycles of the cells were measured by flow cytometry when IC₅₀ concentration of Allicin was adopted. The expression of CDC2 and CyclinB protein were detected by immunohistochemistry.

RESULTS: Allicin inhibited the proliferation of SGC-7901 (IC₅₀ = 23 mg/L) and BGC-823 (IC₅₀ = 35 mg/L) cells and the inhibition rate was elevated with the increase of Allicin concentration. After treatment with IC₅₀ concentration of Allicin, the percentage of G₀/G₁ phase cells was decreased, but that of G₂/M phase ones was significantly increased for both SGC-7901 (24, 48 h vs control: 26.47±2.54%, 28.88±2.75% vs 24.30±2.74%, P <0.01) and BGC-823 (24, 48 h vs control: 22.78±1.45%, 24.87±1.61% vs 20.32±1.34%, P <0.01). CDC2 and CyclinB proteins were positively expressed in SGC-7901 and BGC-823 cells without Allicin treatment. After treatment, the comparative rates of CDC2 and CyclinB expression were 87.2% and 59.3% in SGC-7901 cells, respectively, and 84.4% and 62.8% in BGC-823 cells, respectively (all P <0.01).

CONCLUSION: Allicin causes arrest of SGC-7901 and BGC-823 cells in G₂/M phase, and the mechanism is related to the down-regulation of CDC2 and CyclinB expression.