Cisplatin Resistance In Gastric Cancer Cells Research Articles

Low-dose Diosbulbin-B (DB) activates tumor-intrinsic PD-L1/NLRP3 signaling pathway mediated pyroptotic cell death to increase cisplatin-sensitivity in gastric cancer (GC)

BackgroundEmerging evidences suggests that Diosbulbin-B (DB) is effective to improve cisplatin (DDP)-sensitivity in gastric cancer (GC), but its molecular mechanisms were not fully delineated, and this study managed to investigate this issue.MethodsGenes expressions were determined by Real-Time qPCR and Western Blot at transcriptional and translational levels. Cell proliferation and viability were evaluated by cell counting kit-8 (CCK-8) and trypan blue staining assay. Annexin V-FITC/PI double staining assay was used to examine cell apoptosis. The Spheroid formation assay was used to evaluated cell stemness. The xenograft tumor-bearing mice models were established, and the tumors were monitored and the immunohistochemistry (IHC) was employed to examine the expressions and localization of Ki67 protein in mice tumor tissues.ResultsLow-dose DB (12.5 μM) downregulated PD-L1 to activate NLRP3-mediated pyroptosis, and inhibited cancer stem cells (CSCs) properties, to sensitize cisplatin-resistant GC (CR-GC) cells to cisplatin. Mechanistically, the CR-GC cells were obtained, and either low-dose DB or cisplatin alone had little effects on cell viability in CR-GC cells, while low-dose DB significantly induced apoptotic cell death in cisplatin treated CR-GC cells. In addition, low-dose DB triggered cell pyroptosis in CR-GC cells co-treated with cisplatin, which were abrogated by silencing NLRP3. Next, CSCs tended to be enriched in CR-GC cells, instead of their parental cisplatin-sensitive GC (CS-GC) cells, and low-dose DB inhibited spheroid formation and stemness biomarkers (SOX2, OCT4 and Nanog) expressions to eliminate CSCs in CR-GC cells, which were reversed by upregulating programmed death ligand-1 (PD-L1). Furthermore, we proved that PD-L1 negatively regulated NLRP3 in CR-GC cells, and low-dose DB activated NLRP3-mediated pyroptotic cell death in cisplatin treated CR-GC cells by downregulating PD-L1. Also, low-dose DB aggravated the inhibiting effects of cisplatin on tumorigenesis of CR-GC cells in vivo.ConclusionsCollectively, low-dose DB regulated intrinsic PD-L1/NLRP3 pathway to improve cisplatin-sensitivity in CR-GC cells, and this study provided alternative therapy treatments for GC.

Cisplatin-Resistant Gastric Cancer Cells Promote the Chemoresistance of Cisplatin-Sensitive Cells via the Exosomal RPS3-Mediated PI3K-Akt-Cofilin-1 Signaling Axis.

Cisplatin is an important agent in first-line chemotherapy against gastric cancer (GC). However, consequential drug resistance limits its effectiveness for the treatment of GC. In this study, a cisplatin resistant gastric cancer cell line SGC7901R was determined by LC-MS/MS with increased exosomal levels of RPS3 protein. SGC7901R cell-derived exosomes were readily taken up by cisplatin-sensitive SGC7901S cells, thus triggering off a phenotype of chemoresistance in the receptor cells. Subsequently, it was demonstrated that exosomal RPS3 was essential for inducing chemoresistance of receptor cells as shown by the acquisition of this phenotype in SGC7901S cells with enforced expression of RPS3. Further mechanism study demonstrated that cisplatin-resistant gastric cancer cell-derived exosomal RPS3 enhanced the chemoresistance of cisplatin-sensitive gastric cancer cells through the PI3K-Akt-cofilin-1 signaling pathway. All these findings demonstrated that cisplatin-resistant gastric cancer cells communicate with sensitive cells through the intercellular delivery of exosomal RPS3 and activation of the PI3K-Akt-cofilin-1 signaling pathway. Targeting exosomal RPS3 protein in cisplatin-resistant gastric cancer cells may thus be a promising strategy to overcome cisplatin resistance in gastric cancer.

Roles of E3 ubiquitin ligases in gastric cancer carcinogenesis and their effects on cisplatin resistance.

Although gastric cancer (GC) is one of the most common cancers with high incidence and mortality rates, its pathogenesis is still not elucidated. GC carcinogenesis is complicated and involved in the activation of oncoproteins and inactivation of tumor suppressors. The ubiquitin-proteasome system (UPS) is crucial for protein degradation and regulation of physiological and pathological processes. E3 ubiquitin ligases are pivotal enzymes in UPS, containing various subfamily proteins. Previous studies report that some E3 ligases, including SKP2, CUL1, and MDM2, act as oncoproteins in GC carcinogenesis. On the other hand, FBXW7, FBXL5, FBXO31, RNF43, and RNF180 exert as tumor suppressors in GC carcinogenesis. Moreover, E3 ligases modulate cell growth, cell apoptosis, and cell cycle; thus, it is complicated to confer cisplatin resistance/sensitivity in GC cells. The intrinsic and acquired cisplatin resistance limits its clinical application against GC. In this review, we explore oncogenic and tumor suppressive roles of E3 ligases in GC carcinogenesis and focus on the effects of E3 ligases on cisplatin resistance in GC cells, which will provide novel therapeutic targets for GC therapy, especially for cisplatin-resistant patients.

LncRNA BANCR Attenuates the Killing Capacity of Cisplatin on Gastric Cancer Cell Through the ERK1/2 Pathway.

PurposeChemotherapy-based comprehensive treatments are the most important therapeutic methods for patients with advanced gastric cancer, but chemoresistance often cause treatment failure. Long non-coding RNA (LncRNA) BRAF-activated non-coding RNA (BANCR) has been shown to participate in many biological behaviors of multiple cancers. However, the biological roles of LncRNA BANCR in chemoresistance of gastric cancer remain unclear. Here, we aimed to evaluate the functions of LncRNA BANCR on the therapy of gastric cancer.MethodsIn this study, LncRNA BANCR expression was detected in gastric cancer patient samples and cell lines by quantity polymerase chain reaction (qPCR). Cell proliferation and viability in cisplatin-treated cells were measured using clonogenic survival assay and cell counting kit-8. The levels of ERK1/2 pathway molecules were tested with Western blot. Ly3214996, an inhibitor of ERK signal pathway, was administered to assess the effects of BANCR overexpression on gastric cancer cell with cisplatin-treated resistance. Moreover, the role of BANCR in cisplatin resistance of gastric cancer was validated in xenograft mouse models in vivo.ResultsOur study revealed that LncRNA BANCR expression was also significantly increased in gastric cancer tissues compared with adjacent normal tissues. Furthermore, we found that BANCR overexpression promoted gastric cancer cell resistance to cisplatin in vitro. Ly3214996 treatment abolished the BANCR overexpression-mediated gastric cancer cell cisplatin resistance via regulating the phosphorylation of ERK protein. Knock-down of BANCR significantly delayed tumor growth in xenograft mouse models.ConclusionBANCR promoted cisplatin resistance of gastric cancer cells by activating ERK1/2 pathway. Inhibition of BANCR markedly suppressed the growth of gastric cancer cells in vitro as well as in vivo. These results provided a new strategy for gastric cancer therapy via targeting BANCR.

<p>Circ_0110805 Knockdown Enhances Cisplatin Sensitivity and Inhibits Gastric Cancer Progression by miR-299-3p/ENDOPDI Axis</p>

BackgroundGastric cancer is a prevalent primary stomach tumor. Cisplatin is frequently used to treat gastric cancer. However, the resistance of cisplatin in gastric cancer often occurs, which brings a heavy burden to gastric cancer treatment.MethodsIn this study, we revealed a novel underlying mechanism about cisplatin-resistant effect in gastric cancer. A Cell Counting Kit-8 (CCK-8) cell viability assay and a xenograft model were performed to evaluate the function of circRNA in the cisplatin resistance of gastric cancer.ResultsCompared with control groups, we observed that circ_0110805 was highly expressed, the mRNA and protein expression levels of ENDOPDI were dramatically upregulated, and the expression of miR-299-3p was significantly downregulated in gastric cancer cells, cisplatin-resistant gastric cancer tissues or cells. Functionally, circ_0110805 knockdown improved cisplatin sensitivity, induced cell apoptosis, whereas repressed cell viability, migration and invasion in AGS/DDP and HGC-27/DDP cells, which was reversed by miR-299-3p inhibitor. Additionally, ENDOPDI overexpression hindered the effects of miR-299-3p on cisplatin sensitivity and gastric cancer progression. Circ_0110805 knockdown enhanced cisplatin sensitivity in vivo. Mechanistically, circ_0110805 acted as a sponge of miR-299-3p and its targeted ENDOPDI.ConclusionWe showed that circ_0110805 knockdown increased the sensitivity of gastric cancer to cisplatin, which also repressed gastric cancer progression by sponging miR-299-3p to downregulate ENDOPDI expression. It might provide a new insight for future studying cisplatin-resistant gastric cancer.

LncRNA-SNHG7 interferes with miR-34a to de-sensitize gastric cancer cells to cisplatin.

Gastric cancer (GC) remains poor prognosis and survival issues due to the resistance of chemotherapies, such as cisplatin. The long non-coding RNA small nucleolar RNA host gene 7 (lncRNA-SNHG7) is known as an oncogenic molecule in diverse cancers. Here, we demonstrate that SNHG7 was significantly upregulated in gastric cancer and positively correlated with cisplatin resistance of gastric cancer cells that SNHG7 was significantly upregulated in cisplatin resistant cells. Silencing SNHG7 dramatically sensitized cisplatin resistant cells. In contrast, a negative correlation between lncRNA-SNHG7 and miR-34a was found that miR-34a was downregulated in gastric cancer patient tissues and significantly sensitized cisplatin resistant gastric cancer cells. Intriguingly, bioinformatical analysis indicated miR-34a has putative biding site for SNHG7 and such negative association between SNHG7 and miR-34a was verified in gastric cancer tissues. The cisplatin resistant cells displayed increased glycolysis rate and SNHG7 promoted cellular glycolysis rate of gastric cancer cells. Luciferase assay illustrated LDHA, a glycolysis enzyme, was the direct target of miR-34a. Importantly, inhibiting SNHG7 successfully suppressed LDHA expressions and sensitized cisplatin resistant cells and such inhibitory effects could be recovered by further anti-miR-34a. These findings suggest an important regulator mechanism for the SNHG7-mediated cisplatin resistance via miR-34a/LDHA-glycolysis axis.

Long Noncoding RNA Regulator of Reprogramming Regulates Cell Growth, Metastasis, and Cisplatin Resistance in Gastric Cancer via miR-519d-3p/HMGA2 Axis.

Background: Gastric cancer (GC) is a common tumor found worldwide, and cisplatin is the first-line agent for the treatment of GC. However, the resistance to cisplatin is an obstacle. Here, we explored the biological mechanism of long noncoding RNA regulator of reprogramming (ROR) in the cisplatin resistance of GC. Materials and Methods: ROR, miR-519d-3p, and high mobility group protein A2 (HMGA2) expression in GC tissues and cells were measured by quantitative real-time polymerase chain reaction and Western blot. Cell viability, migration, invasion, and apoptosis were detected by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay, transwell assay, and flow cytometry, respectively. The relative protein expression was detected by Western blot. The interactions between miR-519d-3p and ROR, HMGA2 were predicted using miRcode and starBase v2.0 online database, and then verified by dual luciferase reporter assay and RNA immunoprecipitation assay. In addition, the xenograft tumor mouse model was constructed to verify the biological role of ROR in vivo. Results: The levels of ROR, HMGA2 were significantly upregulated, and miR-519d-3p was apparently downregulated in GC tissues and cells. The miRcode and starBase v2.0 online websites and dual luciferase reporter assay validated that miR-519d-3p directly interacted with ROR and HMGA2. Furthermore, ROR knockdown downregulated HMGA2 to restrain cell proliferation, migration, invasion, epithelial-mesenchymal transition (EMT), and cisplatin resistance in GC cells by targeting miR-519d-3p. In addition, the depletion of ROR repressed the xenograft tumor growth in vivo. Conclusion: In conclusion, we first found the ROR/miR-519d-3p/HMGA2 regulatory network to regulate cell proliferation, migration, invasion, EMT, and cisplatin resistance in GC, and this may shed light on the GC tumorigenesis.

LncRNA ADAMTS9-AS2 inhibits gastric cancer (GC) development and sensitizes chemoresistant GC cells to cisplatin by regulating miR-223-3p/NLRP3 axis

The role of LncRNA ADAMTS9-AS2 in the regulation of chemoresistance of gastric cancer (GC) is largely unknown. Here we found that LncRNA ADAMTS9-AS2 was low-expressed in GC tissues and cells compared to their normal counterparts. In addition, LncRNA ADAMTS9-AS2 inhibited miR-223-3p expressions in GC cells by acting as competing endogenous RNA, and the levels of LncRNA ADAMTS9-AS2 and miR-223-3p showed negative correlations in GC tissues. Of note, overexpression of LncRNA ADAMTS9-AS2 inhibited GC cell viability and motility by sponging miR-223-3p. In addition, the levels of LncRNA ADAMTS9-AS2 were lower, and miR-223-3p was higher in cisplatin-resistant GC (CR-GC) cells than their parental cisplatin-sensitive GC (CS-GC) cells. LncRNA ADAMTS9-AS2 overexpression enhanced the cytotoxic effects of cisplatin on CR-GC cells, which were reversed by overexpressing miR-223-3p. Furthermore, LncRNA ADAMTS9-AS2 increased NLRP3 expressions by targeting miR-223-3p, and upregulation of LncRNA ADAMTS9-AS2 triggered pyroptotic cell death in cisplatin treated CR-GC cells by activating NLRP3 inflammasome through downregulating miR-223-3p. Finally, the promoting effects of LncRNA ADAMTS9-AS2 overexpression on CR-GC cell death were abrogated by pyroptosis inhibitor Necrosulfonamide (NSA). Collectively, LncRNA ADAMTS9-AS2 acted as a tumor suppressor and enhanced cisplatin sensitivity in GC cells by activating NLRP3 mediated pyroptotic cell death through sponging miR-223-3p.

Targeted Inhibition of CCL22 by miR-130a-5p Can Enhance the Sensitivity of Cisplatin-Resistant Gastric Cancer Cells to Chemotherapy.

ObjectiveThis study set out to explore the regulatory mechanism of miR-130a-5p in cisplatin (DDP)-resistant gastric cancer (GC) cells.Materials and MethodsForty cases of GC and paracancerous tissues were collected, and the miR-130a-5p and CCL22 levels were detected by qRT-PCR. DDP-resistant cell lines of GC cells were established. Cell viability, invasion, and apoptosis were measured by CCK-8, Transwell, and flow cytometry, respectively. The relationship between miR-130a-5p and CCL22 was verified by dual-luciferase reporter enzyme, and the protein levels of caspase-3, bax, bcl-2, and CCL22 were determined by Western blot.ResultsmiR-130a-5p was low expressed in GC tissues and cells, while CCL22 showed marked negative correlation, and the area under the curve (AUC) for diagnosing GC was not less than 0.850. Up-regulating miR-130a-5p or knocking down CCL22 expression can inhibit the proliferation and invasion of GC cells and promote their apoptosis, reverse the resistance of NCI-N87/DDP to DDP, and also enhance the chemosensitivity of GC cells. Dual-luciferase reporter enzyme identified that there was a targeted relationship between miR-130a-5p and CCL22. At the same time, miR-130a-5p and CCL22 were up-regulated or down-regulated, and the malignant proliferation, invasion, apoptosis, and DDP chemotherapy resistance of the cells had no difference compared with miR-NC with transfection-unrelated sequences.ConclusionUp-regulating miR-130a-5p can enhance the sensitivity of DDP-resistant GC cells to chemotherapy and regulate their biological function by targeted inhibition of CCL22.

The long noncoding RNA CRAL reverses cisplatin resistance via the miR-505/CYLD/AKT axis in human gastric cancer cells

ABSTRACT Emerging evidence has suggested that long noncoding RNAs (lncRNAs) play an essential role in the tumorigenesis of multiple types of cancer including gastric cancer (GC). However, the potential biological roles and regulatory mechanisms of lncRNA in response to cisplatin, which may be involved in cisplatin resistance, have not been fully elucidated. In this study, we identified a novel lncRNA, cisplatin resistance-associated lncRNA (CRAL), that was downregulated in cisplatin-resistant GC cells, impaired cisplatin-induced DNA damage and cell apoptosis and thus contributed to cisplatin resistance in GC cells. Furthermore, the results indicated that CRAL mainly resided in the cytoplasm and could sponge endogenous miR-505 to upregulate cylindromatosis (CYLD) expression, which further suppressed AKT activation and led to an increase in the sensitivity of gastric cancer cells to cisplatin in vitro and in preclinical models. Moreover, a specific small molecule inhibitor of AKT activation, MK2206, effectively reversed the cisplatin resistance in GC caused by CRAL deficiency. In conclusion, we provide the first evidence that a novel lncRNA, CRAL, could function as a competing endogenous RNA (ceRNA) to reverse GC cisplatin resistance via the miR-505/CYLD/AKT axis, which suggests that CRAL could be considered a potential predictive biomarker and therapeutic target for cisplatin resistance in gastric cancer.

Ubenimex induces autophagy inhibition and EMT suppression to overcome cisplatin resistance in GC cells by perturbing the CD13/EMP3/PI3K/AKT/NF-κB axis

Cisplatin (CDDP)-based chemotherapy is a standard treatment for gastric cancer (GC). However, chemoresistance is a major obstacle for CDDP application. Exploring underlying mechanisms of CDDP resistance development in GC and selecting an effective strategy to overcome CDDP resistance remain a challenge. Here, we demonstrate that a transmembrane ectoenzyme, CD13, endows GC patients with insensitivity to CDDP and predicts an undesirable prognosis in GC patients with CDDP treatment. Similarly, CD13 expression is positively related with CDDP resistance in GC cells. A CD13 inhibitor, Ubenimex, reverses CDDP resistance and renders GC cells sensitivity to CDDP, for which CD13 reduction is essential, and epithelial membrane protein 3 (EMP3) is a putative target downstream of CD13. Furthermore, Ubenimex decreases EMP3 expression by boosting its CpG island hypermethylation for which CD13 down-regulation is required. In addition, EMP3 is a presumptive modifier by which CD13 exerts functions in the phosphoinositol 3-kinase/protein kinase B (PI3K/AKT) pathway. Ubenimex inhibits the activation of the CD13/EMP3/PI3K/AKT/NF-κB pathway to overcome CDDP resistance in GC cells by suppressing autophagy and epithelial-mesenchymal transition (EMT). Therefore, CD13 is a potential indicator of CDDP resistance formation, and Ubenimex may serve as a potent candidate for reversing CDDP resistance in GC.

Establish cisplatin-resistant gastric cancer cell line MGC-803/cisplatin and reveal its mechanism

Objective To establish a cisplatin-resistant gastric cancer cell line MGC-803/cisplatin (DDP) and to explore its drug resistance mechanism. Methods The cisplatin was used to induce the drug resistance of MGC-803 cells. The half maximal inhibitory concentration (IC50) of the drug-resistant strains was detected by the cell counting kit-8 (CCK-8) method. The expression of chloride intracellular channel 1 (CLIC1) was detected by Western blotting analyses. The wild-type CLIC1 plasmid and the short hairpin RNA (shRNA) plasmid targeting CLIC1 were constructed. After Lipo3000 was transfected into gastric cancer cells, the IC50 of gastric cancer cells to cisplatin was detected, and then the intracellular Cl-concentration was detected by MQAE fluorescent probe. Results The cisplatin-resistant cell line MGC-803/DDP was successfully induced with an IC50 of (7.02±0.13) mg/L, while the IC50 of MGC803 was (1.29±0.09) mg/L, (t=36.090, P<0.05). The CLIC1 protein of MGC803/DDP was up-regulated by (2.27±0.15) times relative to MGC803 (t=7.841, P<0.05). After silencing the CLIC1 gene of MGC803/DDP, the IC50 of the CON, CN, and KD groups were (6.96±0.09), (6.93±0.15) and (3.02±0.20) mg/L, respectively, which was significantly decreased in the KD group (F=0.209, P<0.05). After overexpression of the CLIC1 gene in MGC803 cells, the IC50 of the CON, CN, and OE groups were (1.35±0.07), (1.25±0.07) and (4.77±0.12) mg/L, respectively, and the OE group was significantly elevated (F=0.508, P<0.05). The concentration of chloride ion was detected by MQAE. The relative fluorescence intensity of MGC-803, MGC-803/OE, MGC-803/DDP and MGC-803/DDP-KD were (1.02±0.03), (0.61±0.02), (0.67±0.01) and (1.39±0.02), respectively. The concentration of Cl- in MGC-803/OE cells was higher than that in MGC-803 (t=10.800, P<0.05), while the concentration of Cl- in MGC-803/DDP was higher than that in MGC-803 and MGC-803/DDP-KD, and the concentration of Cl- in KD group was the lowest (F=229, P<0.05). Conclusion The CLIC1 gene can induce the resistance of gastric cancer cell line MGC-803 to cisplatin in vitro. The mechanism may be related to the up-regulation of CLIC1 expression, which leads to an increase of intracellular chloride ion concentration. Key words: Gastric cancer; Chloride intracellular channel 1; Cisplatin; Drug resistance

Exosome-Mediated Transfer of lncRNA HOTTIP Promotes Cisplatin Resistance in Gastric Cancer Cells by Regulating HMGA1/miR-218 Axis.

BackgroundChemoresistance has become a major obstacle for cancer therapy in clinic. Long noncoding RNAs (lncRNAs) have been reported to play critical roles in the development of chemoresistance in various tumors, including gastric cancer (GC). However, the role of HOXA transcript at the distal tip (HOTTIP) within extracellular vesicles (exosomes) in cisplatin-resistant GC cells remains largely unknown.Materials and methodsCell proliferation, migration and invasion were detected using Cell Counting Kit-8 (CCK-8) and transwell assays, respectively. Western blot assay was employed to analyze the protein levels of E-cadherin, N-cadherin, Vimentin, CD63, CD83, GRP78, HMGA1, and high-mobility group A1 (HMGA1). The expression levels of HOTTIP, microRNA-218 (miR-218) and HMGA1were measured by quantitative real-time polymerase chain reaction (qRT-PCR). The interaction between miR-218 and HOTTIP or HMGA1 was predicted by bioinformatics software and confirmed by the dual-luciferase reporter and RNA immunoprecipitation (RIP) assays.ResultsCell proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT) were promoted in cisplatin-resistant GC cells. HOTTIP level was upregulated in cisplatin-resistant GC cells and its downregulation enhanced cisplatin sensitivity. Moreover, extracellular HOTTIP could be incorporated into exosomes and transmitted to sensitive cells, thus disseminating cisplatin resistance. Additionally, exosomal HOTTIP promoted cisplatin resistance via activating HMGA1 in GC cells. Interestingly, HMGA1 was a target of miR-218 and miR-218 could directly bind to HOTTIP. Clinically, high expression of exosomal HOTTIP in serum was associated with poor response to cisplatin treatment in GC patients.ConclusionExosomal HOTTIP contributed to cisplatin resistance in GC cells by regulating miR-218/HMGA1 axis, providing a novel avenue for the treatment of GC.

MiR-187 influences cisplatin-resistance of gastric cancer cells through regulating the TGF-β/Smad signaling pathway.

To explore the effect of micro-ribonucleic acid (miR)-187 on cisplatin (DDP) resistance of gastric cancer cells by regulating the transforming growth factor-β (TGF-β)/Smad signaling pathway. DDP-sensitivities in GES-1, SGC7901, and SGC7901/DDP cells were detected via Cell Counting Kit-8 (CCK-8) assay. The differential expression of miR-187 of these cell lines was detected by Reverse Transcription-quantitative Polymerase Chain Reaction (RT-qPCR). DDP-resistant gastric cancer cells SGC7901/DDP were divided into control group (blank control), miR-187 inhibitor group (SGC7901/DDP cells transfected with miR-187 inhibitor), and miR-187 mimic group (SGC7901/DDP cells transfected with miR-187 mimic). The protein expressions of miR-187, TGF-β1, p-Smad4, excision repair cross-complementation group 3 (ERCC3), and ERCC4 were determined through RT-qPCR, immunohistochemistry, and Western blotting. The apoptosis in each group was detected by flow cytometry. MiR-187 level had a negative correlation with DDP-resistance of GES-1, SGC7901, and SGC7901/DDP cells, and among them, the GES-1 cells had the lowest DDP-resistance and the highest expression of miR-187. CCK-8 assay revealed that compared with that in the control group, DDP-resistance significantly declined in the miR-187 mimic group, while it was significantly enhanced in miR-187 inhibitor group (p<0.01). According to the results of flow cytometry, after treatment with 100 nM DDP for 12 h, the apoptotic rate in miR-187 mimic group enhanced, while it was markedly reduced in the miR-187 inhibitor group (p<0.01). Western blotting and immunohistochemistry results showed that expressions of TGF-β1 and p-Smad4 were significantly downregulated in the miR-187 mimic group, while they were upregulated in the miR-187 inhibitor group (p<0.01). Besides, compared with the control group, ERCC3 and ERCC4 were downregulated in the miR-187 mimic group, while upregulated in miR-187 inhibitor group (p<0.01). The overexpression of miR-187 alleviates DDP-resistance in gastric cancer cells by inhibiting the TGF-β/Smad signaling pathway.

α-Hederin Increases The Apoptosis Of Cisplatin-Resistant Gastric Cancer Cells By Activating Mitochondrial Pathway In Vivo And Vitro.

IntroductionGastric cancer remains an important cancer worldwide, and conventional chemotherapeutic drugs have the defects of drug resistance and cell toxicity. α-Hederin has been found to have certain therapeutic effects on various types of human cancers. However, studies on the α-hederin that exert biological activities on the cisplatin-resistant gastric cancer cells are limited. In this study, we evaluated the effects of α-hederin in HGC27/DDP and the potential mechanisms both in vivo and in vitro.MethodsHGC27/DDP cells were cultured in DMEM/F12 medium. Cell proliferation and viability were assessed quantitatively using Cell Counting Kit-8. Cell invasion and migration were detected by Transwell invasion assay and wound healing assay. Cell apoptosis was examined by employing Hoechst 33258 Staining Kit and an Annexin V-PE apoptosis kit. Intracellular GSH levels were examined by using a GSH Assay Kit. DCFH-DA and JC-1 Kit were used to detect levels of intracellular reactive oxygen species (ROS) and changes in mitochondrial membrane potential (∆Ψm). The protein levels of Apaf-1, AIF, Bax, Bcl-2, Cyt C, Survivin, cleaved caspase-3, cleaved caspase-9, MMP-9 and MMP-2 were detected by Western blot analysis. The effect of α-hederin in vivo was observed by xenograft tumor models in nude mice.ResultsThe α-hederin treatment significantly inhibited the proliferation in a dose- and time-dependent manner of HGC27/DDP and induced obvious apoptosis compared with the control group (P<0.05). Meanwhile, the ability of cells to invade and migrate was suppressed (P<0.05). The α-hederin induced the depletion of GSH (P<0.05) and the accumulation of intracellular ROS (P<0.05), changed the mitochondrial membrane potential (P<0.05), increased the Bax, Apaf-1, AIF, Cyt C, cleaved caspase-3 and cleaved caspase-9 expression and decreased the protein level of Bcl-2, survivin, MMP-9 and MMP-2 (P<0.05). Pretreatment with NAC (12 mM) enhanced the tendency and pretreatment with BSO (8 mM) attenuated the tendency above (P<0.05). Meanwhile, α-hederin inhibited xenograft tumor growth in vivo (P<0.05).ConclusionOur study provides strong molecular evidence to support our hypothesis that α-hederin inhibits the proliferation and induces the apoptosis of HGC27/DDP cells by increasing the levels of intracellular ROS and triggering mitochondrial pathway activation.

Potential role of TET2 in gastric cancer cisplatin resistance

Gastric cancer (GC) represents one of the most predominant malignancies with high incidence and mortality rates. Although traditional chemotherapeutics, including cisplatin are effective in the treatment of GC, patients often develop drug resistance in clinic. The present study aimed to explore the underlying mechanism of cisplatin-induced drug resistance in GC. The potential role of DNA demethylase ten-eleven translocation-2 (TET2) in modulating cisplatin resistance of GC cells was investigated. It was observed that TET2 was significantly decreased in cisplatin resistance SGC7901/DDP cells compared with non-resistant cells and TET2 overexpression markedly reduced the tolerance to cisplatin. Additionally, evidence was provided that TET2 regulated interleukin-6 levels in the tumor microenvironment through histone acetylation and therefore served an important role in the development of cisplatin resistance in GC cells. Taken together, the results suggested that TET2-mediated cisplatin resistance may represent a novel mechanism of drug resistance in GC cells and may offer novel treatment approaches.

PCAT-1 contributes to cisplatin resistance in gastric cancer through epigenetically silencing PTEN via recruiting EZH2.

The aim of this study was to investigate the functional role and the underlying molecular mechanism of long noncoding RNA (lncRNA) prostate cancer-associated transcript 1 (PCAT-1) in cisplatin resistance of gastric cancer (GC). Our results indicated that PCAT-1 was overexpressed in CDDP-resistant GC tumor tissues and cell lines. High expression of PCAT-1 was closely correlated with short overall survival in patients with GC. Downregulation of PCAT-1 resensitized CDDP-resistant GC cells to cisplatin. In addition, PCAT-1 epigenetically silenced PTEN through binding to the histone methyltransferase enhancer of zeste homolog 2 (EZH2), thus increasing H3K27me3. More importantly, PTEN silencing counteracted PCAT-1 knockdown-mediated enhancement in cisplatin sensitivity of CDDP-resistant GC cells. In summary, PCAT-1 led to cisplatin resistance in GC cells through epigenetically suppressing PTEN expression, providing a novel therapeutic strategy for GC patients with chemoresistance.

Effect of down-regulation of miR-221 on cell proliferation and cisplatin sensitivity in cisplatin-resistant gastric cancer cells and underlying mechanism

Effect of down-regulation of miR-221 on cell proliferation and cisplatin sensitivity in cisplatin-resistant gastric cancer cells and underlying mechanism

LncRNA SNHG5 promotes cisplatin resistance in gastric cancer via inhibiting cell apoptosis.

To elucidate the function of long non-coding RNA (lncRNA) SNHG5 in cisplatin-resistant gastric cancer (GC), and its potential mechanism. We detected the expressions of SNHG5, apoptosis-specific genes (Bax and Bcl-2) and drug resistance-specific genes (MDR1 and MRP1) in cisplatin-sensitive and cisplatin-resistant GC patients. The expression levels were also detected in cisplatin-resistant GC cell lines (BGC823/DDP, SGC7901/DDP) and GC cell lines (BGC823 and SGC7901). Through the liposome transfection, the regulatory effects of SNHG5 on proliferative potential and apoptosis were examined by cytotoxicity assay and flow cytometry assay, respectively. The protein levels of apoptosis-related genes and drug resistance-related genes influenced by SNHG5 were detected by Western blot. Compared with cisplatin-sensitive GC patients, SNHG5 expression was remarkably higher in cisplatin-resistant GC patients. Besides, higher SNHG5 expression was observed in BGC823/DDP and SGC7901/DDP cells relative to that of their parental cells. Proliferative rate (OD450) and IC50 decreased, but the apoptotic rate increased in BGC823/DDP and SGC7901/DDP cells with SNHG5 knockdown. It is found that SNHG5 overexpression reduced cisplatin sensitivity in BGC823 and SGC7901 cells. Decreased cisplatin cytotoxicity, elevated IC50 and inhibited apoptotic rate were observed in GC cells overexpressing SNHG5. Moreover, the expression levels of Bax, MDR1 and MRP1 were upregulated, while Bcl-2 downregulated in BGC823 and SGC7901 cells overexpressing SNHG5. SNHG5 is highly expressed in cisplatin-resistant GC. SNHG5 promotes cisplatin resistance in GC by regulating apoptosis-related genes and drug resistance-related genes.

Effect of PLK1 inhibition on cisplatin-resistant gastric cancer cells.

This study aims to investigate the effect of polo-like kinase 1 (PLK1) inhibition on cisplatin (DDP)-resistant gastric cancer (GC) cells. The transcriptional level of PLK1 was measured by quantitative reverse-transcription polymerase chain reaction. Expressions of PLK1 and its downstream mediators as well as autophagy-related protein LC3 I/LC3 II were detected by western blot. An 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and 5-ethynyl-2'-deoxyuridine immunofluorescent staining were conducted to evaluate the cell viability and replication activity separately. Flow cytometry was carried out to determine the cell cycle status. TheGFP-LC3 vector contributed toward tracking the formation and aggregation of autophagosomes. Drug-resistant SGC-7901/DDP cells showed insignificant changes in all phases after DDP treatment, including DNA replication, cell proliferation, cell cycle, and apoptosis, whereas DDP could significantly improve the autophagy level of SGC-7901/DDP as well as PLK1expression. By downregulating the expression of PLK1, both BI2536 andsi-PLK1 enhanced SGC-7901/DDP sensitivity to DDP, suppressing the proliferation and autophagy as well as improving the apoptosis rate. PLK1 inhibition also resulted in the repression of cell division regulators CDC25C and cyclin B1. Together, our experimental results illustrated that the DDP resistance of GC cells might be associated with the aberrant overexpression of PLK1. PLK1 inhibition, including si-PLK1 and BI2536 treatment, could restore the chemosensitivity of drug-resistant SGC-7901/DDP cells and enhance the efficacy of DDP, revealing the potential value of PLK1 inhibition in GC chemotherapy.