Chemosensitivity Of Gastric Cancer Cells Research Articles

Regulatory mechanism of ZNF139 in multi-drug resistance of gastric cancer cells

Our previous study found increased zinc finger protein 139 (ZNF139) expression in gastric cancer (GC) cells. Purpose of the study is to further clarify the role and mechanism of ZNF139 in multi-drug resistance (MDR) of GC cells. MTT assay, RT-PCR, Western blotting were employed to detect susceptibility of GC cells to chemotherapeutic agents (5-FU, L-OHP) in vitro, and expressions of ZNF139 and MDR associated genes MDR1/P-gp, MRP1, Bcl-2, Bax were also detected. siRNA specific to ZNF139 was transfected into MKN28 cells, then chemosensitivity of GC cells as well as changes of ZNF139 and MDR associated genes were detected. It's found the inhibition rate of 5-FU, L-OHP to well-differentiated GC tissues and cell line was lower than that in the poorly differentiated tissues and cell line; expressions of ZNF139 and MDR1/P-gp, MRP1 and Bcl-2 in well-differentiated GC tissues and cell line MKN28 were higher, while Bax expression was lower. After ZNF139-siRNA was transfected into MKN28, ZNF139 expression in GC cells was inhibited by 90%; inhibition rate of 5-FU, L-OHP to tumor cells increased, and expressions of MDR1/P-gp, MRP1 and Bcl-2 were down-regulated, while Bax was up-regulated. ZNF139 was involved in GC MDR by promoting expressions of MDR1/P-gp, MRP1 and Bcl-2 and inhibiting Bax simultaneously.

MiR-449a Regulates Proliferation and Chemosensitivity to Cisplatin by Targeting Cyclin D1 and BCL2 in SGC7901 Cells

Recently, several miRNAs have been determined as tumor suppressors in various cancers, such as microRNA-449a. However, the exact molecular mechanisms underlying miR-449a regulated cell proliferation and chemosensitivity in gastric cancer cells have not been well documented. The present study was designed to test whether miR-449a mediates cell proliferation and chemosensitivity in gastric cancer cells via regulating cyclin D1 and BCL2. In vitro, the ability of cell proliferation and cell viability were measured by MTT assay; cell cycle and cell apoptosis was detected by FCM. qRT-PCR was used to measure the expression of miR-449a. Western blot and real-time PCR assays were used to detect the expression of cyclin D1 and BCL2 in gastric cancer cell line SGC7901. miR-449a expression was downregulated in gastric cancer cell line SGC7901 and human gastric cancer tissues, compared to the gastric epithelial cell line GES-1 and matched non-tumor associated tissues. Upregulation of miR-449a reduced the proliferation of SGC7901 cells. Ectopic expression of miR-449a decreased the percentage of S phase cells, increased the percentage of G1/G0 phase cells and increased the apoptosis induced by cisplatin. Moreover, miR-449a inhibited SGC7901 cells proliferation and enhanced cisplatin chemosensitivity by downregulating expression of BCL2 and cyclin D1, respectively, via directly targeting the 3'-untranslated regions of BCL2 and cyclin D1 mRNA. This is the first report to provide evidence that miR-449a could modulate cell cycle and apoptosis through regulating cyclin D1 and BCL2 expression in SGC7901 cells.

Proton pump inhibitor selectively suppresses proliferation and restores the chemosensitivity of gastric cancer cells by inhibiting STAT3 signaling pathway

Recent studies reported that pretreatment of proton pump inhibitors (PPIs) induced sensitization to chemotherapeutic agents in several cancer cells. The devastating effects of PPIs on tumor cells were discovered and raised great interests; therefore we designed the following experiments to fully explain the direct antitumor effects of PPIs. We compared the viability of gastric cancer cells and epithelia cells in buffered and unbuffered culture conditions with PPZ treatment by WST-8 assay. The sensitivity to cisplatin of gastric cancer cells with/without PPZ pretreatment was assessed by IC50 calculation and Annexin V/PI assay. The secretion of IL-6 was detected by ELISA. Western blot analysis and real time RT-PCR were used to evaluate the expression and activation of STAT3 and its downstream targets. PPZ selectively exhibited a dose-dependent cytotoxic effect of gastric cancer cells in acidic unbuffered medium. Low dose of PPZ pretreatment (20 μg/mL) enhanced the sensitivity to cisplatin in gastric cancer cells. PPZ induced cell apoptosis and reduced the secretion of the pro-inflammatory cytokine IL-6 specifically in gastric cancer cells, but had no effect on the epithelia cells. Consequently, the activation of STAT3, not the total amount, was suppressed by PPZ in gastric cancer cells. The downstream targets of STAT3, c-Myc, cyclin D1 and Bcl-2 were also down-regulated. PPZ causes gastric cancer cell death by induction of apoptosis and its mechanism of action is mediated in part via the inhibition of IL-6/STAT3 pathway.

Knockdown of Inhibitor of Growth Protein 2 Inhibits Cell Invasion and Enhances Chemosensitivity to 5-FU in Human Gastric Cancer Cells

The inhibitor of growth (ING) family is involved in multiple cellular functions, but the role of ING2 in gastric cancer progression is unclear. To investigate the effects of ING2 gene knockdown on chemosensitivity to 5-fluorouracil (5-FU) in human gastric cancer cells and its possible mechanisms. Short hairpin RNA (shRNA) targeting ING2 (shING2) was transfected into MGC-803 cells using Lipofectamine 2000, and stable transfection cell lines were established using G418. Cell viability, cell cycle distribution, cell apoptosis, and invasive ability were measured to determine the influence of ING2 knockdown on cell biologic characteristics. Messenger RNA (mRNA) and protein levels of ING2, cyclin D1, NF-kappaB/p65, and several matrix metalloproteinases (MMPs) were determined by use of real-time polymerase chain reaction (PCR) or Western blotting, respectively. Our results showed that ING2 knockdown induced cell apoptosis and inhibited cell viability significantly (P < 0.05). Additionally, ING2 knockdown induced a specific G0/G1 arrest. Furthermore, the suppression of ING2 could enhance the chemosensitivity of gastric cancer cells to 5-FU significantly. Moreover, knockdown of ING2 expression significantly reduced cellular metastatic ability and expression of MMPs in MGC-803 cells. The expression of cyclin D1 and NF-kappaB/p65 was also markedly inhibited in MGC-803/shING2 cells compared with control cells. ING2 not only plays an essential role in the growth and invasion of MGC-803 cells but also represents a potential approach to chemosensitization therapy in human gastric cancer.

Inhibition of the PI3K/Akt pathway increases the chemosensitivity of gastric cancer to vincristine

The phosphatidylinositol 3‑kinase (PI3K)/Akt signaling pathway plays a crucial role in tumorigenesis and tumor progression by promoting cell proliferation and inhibiting apoptosis, a process closely associated with multidrug resistance (MDR) of tumors. LY294002 is a commonly used pharmacological inhibitor that acts at the ATP‑binding site of the PI3K enzyme, selectively inhibiting the PI3K/Akt pathway. In the present study, we evaluated the effect of LY294002 on the chemosensitivity of gastric cancer cells to vincristine (VCR) in vitro and in vivo and investigated the possible underlying cellular mechanisms. The effect of LY294002 on cell viability, apoptosis induction and inhibition of tumor growth was analyzed using MTT and TUNEL assay in invitro and invivo models of gastric cancer. Intracellular accumulation of VCR was determined by high performance liquid chromatography. The activity of the PI3K/Akt pathway was evaluated by western blot analysis. Furthermore, reverse transcription PCR and immunohistochemistry were performed to determine the mRNA and protein expression levels of MDR1/ P-glycoprotein (P‑gp) and apoptosis‑related factors. We found that gastric cancer cells treated with LY294002 showed a significant inhibition of PI3K/Akt activity. The PI3K inhibitor LY294002 combined with VCR worked synergistically to promote growth inhibition, induce apoptosis and increase the intracellular drug accumulation in gastric cancer cell lines. Similarly, LY294002 could cooperate with VCR to reduce tumor growth in a gastric cancer model invivo. Finally, LY294002 was able to decrease the expression of MDR1/P‑gp, Bcl‑2 and XIAP, and upregulate expression of Bax and caspase‑3, thereby enhancing chemosensitivity to VCR by inhibiting a drug pump and inducing apoptosis. These results suggested that the PI3K/Akt inhibitor LY294002 can enhance chemosensitivity of human gastric cancer to VCR. This preclinical evaluation of a rational combination of LY294002 and VCR may provide a new strategy to resolve the MDR of gastric cancer.

Tu1598 Proton Pump Inhibitor Selectively Suppresses Proliferation and Restores the Chemosensitivity of Gastric Cancer Cells by Inhibition of STAT3 Signaling Pathway

Tu1598 Proton Pump Inhibitor Selectively Suppresses Proliferation and Restores the Chemosensitivity of Gastric Cancer Cells by Inhibition of STAT3 Signaling Pathway

Overexpression of AKT decreases the chemosensitivity of gastric cancer cells to cisplatin in vitro and in vivo

Cisplatin (CDDP) is one of the most efficacious and widely used cytotoxic anticancer drugs used for the treatment of numerous types of cancer. However, its efficacy is limited as a result of acquired drug resistance. AKT overexpression may provide a potential mechanism leading to the resistance of human gastric cancer cells; however, the precise mechanism of the development of CDDP drug resistance remains uncertain. In the present study, we demonstrate that CDDP resistance is associated with AKT overexpression at the cellular and molecular level. We also observed that increased expression levels of AKT were sufficient to inhibit the resistance of gastric cancer cells to CDDP and that overexpressed AKT interacted with reactive oxygen species which were generated by CDDP. These results indicate that AKT activity is essential for the regulation of CDDP resistance in gastric cancer cells. Our results further demonstrate that AKT induces gastric cancer cells to become resistant to CDDP through the Janus kinase2 (JAK2)/signal transducer and activator of transcription3 (STAT3) signaling pathway. Taken together, these data support a potential role for AKT overexpression and the JAK2/STAT3 pathway in the development of CDDP drug resistance in human gastric cancer cells. We hypothesize that AKT may represent a future pharmacological target for the inhibition of CDDP resistance in human cancer.

Effect of trastuzumab on telomere-related proteins and the relationship to the sensitivity of HER2-amplified human gastric cancer cells to oxaliplatin and cisplatin.

53 Background: HER2 amplification occurs in about 20% of gastric cancers, and trastuzumab in combination with cisplatin based chemotherapy has been reported to improve oncological outcomes in gastric and gastro-oesophageal junction cancer with HER2 gene amplification. The aim of this study was to evaluate the potentially useful combined antitumor efficacy of trastuzumab and platinum agents in gastric cancer cells and to elucidate further the mechanisms possibly involved in the interaction between the trastuzumab and platinum agents. Methods: Gene expression was determined by using real-time quantitative PCR in gastric cancer cell lines. The chemosensitivity of gastric cancer cells to platinum agents and the apoptotic effect of drugs in vitro were evaluated using cellTiter 96 Aqueous One Solution Cell Proliferation Assay kit and double staining with both Annexin-V-FITC and PI, respectively. Results: Treatment with 1.0μg/ml trastuzumab for 48h could significantly increase sensitivity of oxaliplatin or cisplatin in HER2 amplified gastric cancer cells, and the IC50 of oxaliplatin and cisplatin were reduced to about 3.29 times and 6.91 times, respectively. Apoptosis analysis also indicated that trastuzumab significantly increased both oxaliplatin and cisplatin-induced apoptosis in NCI-N87 cells. Analysis of telomere-related genes revealed that trastuzumab singly and pretreatment with trastuzumab for 48h followed by oxaliplatin or cisplatin for another 48h could significantly downregulate the mRNA expression of TPP1, TRF1, TRF2, TRF2IP, POT1 and TIN2 genes. Conclusions: Our results describe the potential role of low dose trastuzumab to increase sensitivity of oxaliplatin and cisplatin in HER2 amplified gastric cancer cells, which may be partially through downregulating the expression levels of telomere-related genes.

The effects of ERCC1 expression levels on the chemosensitivity of gastric cancer cells to platinum agents and survival in gastric cancer patients treated with oxaliplatin-based adjuvant chemotherapy

Excision repair cross-complementing 1 (ERCC1) is reported to be involved in the sensitivity of cancer cells to platinum-based chemotherapy. The present study was designed to evaluate the effects of ERCC1 expression on the chemosensitivity of platinum agents in gastric cancer cell lines, and on survival in gastric cancer patients treated with surgery followed by oxaliplatin-based adjuvant chemotherapy. ERCC1 expression levels were measured by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and western blot analysis, respectively. The chemosensitivity of a series of gastric cancer cell lines to platinum agents in vitro was evaluated using CellTiter 96 Aqueous One Solution Cell Proliferation Assay kit. The apoptotic effect of the drugs was evaluated by double staining with Annexin-V-fluorescein isothiocyanate (FITC) and propidium iodide (PI). The results demonstrated that the expression levels of ERCC1 mRNA were correlated with the chemosensitivity of platinum agents, and depletion of ERCC1 sensitized the relatively resistant MKN45 cells to cisplatin and oxaliplatin. Univariate analyses revealed that patients with low ERCC1 levels had longer relapse-free survival (RFS) and overall survival (OS) than those with high ERCC1 levels (median RFS, 18 vs. 7 months, P=0.001; median OS, 27 vs. 11 months, P=0.001). Multivariate analyses suggested that high ERCC1 expression is an independent prognostic marker of poor RFS [hazard ratio (HR), 2.16; 95% confidence interval (CI), 1.09–4.25; P= 0.026] and OS (HR, 2.21; 95% CI, 1.07–4.55; P=0.031). These results suggest that overexpression of ERCC1 is correlated with platinum drug resistance in gastric cancer cells, and that depletion of ERCC1 sensitizes gastric cancer cell lines to cisplatin and oxaliplatin. Gastric cancer patients with low levels of ERCC1 expression demonstrate a benefit from oxaliplatin-based adjuvant chemotherapy.

Upregulation of periostin prevents P53-mediated apoptosis in SGC-7901 gastric cancer cells

Periostin is frequently upregulated in human cancers including gastric cancer and implicated in cancer cell proliferation, invasion, and epithelial-mesenchymal transition. This study was undertaken to investigate the effects of periostin overexpression on the chemosensitivity of gastric cancer cells. We constructed a stable cell line overexpressing periostin in SGC-7901 human gastric cancer cells. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay revealed that periostin had no influence on the proliferation of SGC-7901 cells. Compared to empty vector-transfected cells, overexpression of periostin rendered SGC-7901 cells more resistant to cisplatin or 5-fluorouracil (5-FU)-induced apoptosis, accompanying with less release of cytochrome c from mitochondria and diminished cleavage of caspase-3 and poly (ADP-ribose) polymerase. Periostin-overexpressing cells treated with cisplatin or 5-FU showed significantly (p<0.05) decreased expression of Bax and p53 proteins and increased expression of Bcl-2 protein, when compared to drug-treated mock counterparts. Restoration of p53 expression by delivering wild-type p53 gene resulted in a marked increase in drug-induced apoptosis in periostin-overexpressing SGC-7901 cells. Periostin overexpression elevated the phosphorylation of Akt. Pretreatment of periostin-overexpressing cells with an Akt inhibitor, MK-2206, partially rescued periostin-mediated inhibition of p53 expression and drug resistance. Taken together, our data indicate that periostin confers protection against cisplatin or 5-FU-induced apoptosis in SGC-7901 cells, likely through modulating the Akt/p53 pathway, and thus represents a potential therapeutic target in gastric cancer.

Survivin Knockdown Enhances Gastric Cancer Cell Sensitivity to Radiation and Chemotherapy In Vitro and in Nude Mice

IntroductionThe aim is to assess the effect of survivin knockdown on the radio- and chemosensitivity of gastric cancer cells in vitro and in nude mice. MethodsSurvivin messenger RNA and protein were detected by semiquantitative reverse transcription-polymerase chain reaction and Western blot. Survivin and control small hairpin RNA (shRNA) expression constructed vectors were stably transfected into gastric cancer SGC7901 cells. The cells were in turn subjected to irradiation, cisplatin or fluorouracil (5-FU) treatment for colony formation, methyl-thiazolyl-tetrazolium cell viability and flow cytometry assays in vitro. An in vivo nude mouse xenograft assay was performed to assess the effects of Survivin knockdown on regulation of the sensitivity of SGC7901 cells to irradiation, cisplatin or 5-FU treatment. ResultsSurvivin shRNA markedly inhibited levels of survivin messenger RNA and protein in SGC7901 cells and significantly increased sensitivity of the tumor cells to radiation treatment, ie, the mean lethal and quasi-threshold doses in survivin shRNA-transfected cells were significantly lower than that of the negative control shRNA-transfected and parental cells. The same is true for cisplatin- and 5-Fu-treated tumor cells, ie, colony formation and cell viability of the survivin-knocked down SGC7901 cells were reduced, while apoptosis was induced compared with the control cells. Furthermore, the xenograft assay showed survivin knockdown in SGC7901 cells suppressed tumor formation and growth compared with the controls. ConclusionsKnockdown of survivin expression enhanced sensitivity of gastric cancer cells to radiation, cisplatin and 5-FU treatment in vitro and in nude mice. These results demonstrate that clinical trails are warranted of survivin shRNA as an adjuvant therapy for gastric cancer patients.

RNAi knockdown of the Akt1 gene increases the chemosensitivity of gastric cancer cells to cisplatin both in vitro and in vivo

AimTo examine the in vitro and in vivo effects of a combined treatment of cis-d iamminedichloroplatinum(II) (cisplatin) with downregulation of Akt1 expression in gastric cancer cells. Materials and methodsLentivirus-mediated RNA interference (RNAi) was used to silence the Akt1 gene. pGCSIL-Akt1 small hairpin RNA (shRNA) was stably transfected into gastric cancer cells (SGC7901 and BGC823). Next, the effects of Akt1 downregulation on the growth and apoptosis of SGC7901 (BGC823) cells in the presence or absence of cisplatin were investigated by real-time polymerase chain reaction (RT-PCR), Western blot analysis, MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-d-iphenyltetrazolium bromide) assay, Hoechst assay, flow cytometric analysis of annexin V-FITC/PI staining, and TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling). Finally, the effects of downregulation of Akt1 expression on the sensitivity of SGC7901 cells in a tumor xenograft model of cisplatin were also determined. ResultAkt1 silencing reduced gastric cancer proliferation and increased cell apoptosis both in vitro and in vivo. The chemosensitivity of SGC7901 (BGC823) cells to cisplatin increased significantly following the downregulation of Akt1 expression, which might be associated with the inactivation of the PI3K/Akt1 signaling pathway, followed by the induced expression of the pro-apoptotic protein Bax and a concomitant decrease of Bcl-2 expression. ConclusionThis study confirmed that downregulation of Akt1 reduced chemotherapy tolerance of gastric cancer cells to cisplatin treatment. Thus, Akt1 silencing and cisplatin appear to be an effective combination treatment strategy for gastric cancer.

Overexpression of interferon regulatory factor 1 enhances chemosensitivity to 5-fluorouracil in gastric cancer cells

To investigate the effects of interferon regulatory factor 1 (IRF-1) gene overexpression on chemotherapeutic sensitivity of gastric cancer cells. An AGS cell system with tetracycline-inducible IRF-1 expression (AGS/IRF-1) was established. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blotting were used to detect the expression of the IRF-1 gene. Chemosensitivity to 5-fluorouracil (5-FU) was assessed by cell proliferation assay and cell apoptosis. IRF-1 mRNA and protein level were significantly increased in AGS/IRF-1 cells induced with tetracycline. Compared with control cells, the growth inhibition rate of cells with IRF-1 overexpression was significantly increased when treated with 5-FU (P<0.01). Treatment with 5 μmol/l 5-FU resulted in 12.6% apoptotic cells, whereas such treatment after overexpression of IRF-1 resulted in 39.4% apoptotic cells. Moreover, more poly(adenosine diphosphate-ribose) polymerase (PARP) cleavage was seen in cells with IRF-1 overexpression. Overexpression of IRF-1 enhanced the chemosensitivity of gastric cancer cells to 5-FU through induction of apoptosis.

Overexpression of Nampt in gastric cancer and chemopotentiating effects of the Nampt inhibitor FK866 in combination with fluorouracil

Nicotinamide phosphoribosyltransferase (Nampt), an enzyme involved in the NAD⁺ salvage pathway, is over-expressed and important in the carcinogenesis in several types of cancers. The expression of Nampt and its role in gastric cancer remain largely unknown. In this study, using real-time PCR and Western blotting we found that Nampt was overexpressed at the mRNA and protein levels, respectively, in established gastric cancer cells and human gastric cancer tissues. The specific Nampt inhibitor FK866 repressed gastric cancer cell proliferation, as assessed by MTT assay. Using transwell and soft agar clonogenic assays, we also found that FK866 suppressed gastric cancer cell migration and anchorage-independent growth, respectively. These inhibitory effects of FK866 were accompanied by significantly decreased expression of VEGF, MMP2, MMP9 and NF-κB. As determined by MTT assay and flow cytometry, FK866 also increased the chemo-sensitivity of gastric cancer cells to fluorouracil by greater inhibition of cell proliferation and the induction of apoptosis. Our findings indicate that Nampt may be a new therapeutic target for gastric cancer.

Targeted inhibition of COX-2 expression by RNA interference suppresses tumor growth and potentiates chemosensitivity to cisplatin in human gastric cancer cells

Although selective cyclooxygenase-2 (COX-2) inhibitors suppress cell proliferation in gastric cancer, it remains debatable whether their effect is mediated through COX-2 dependent or independent pathways. We investigated the effects of the targeted inhibition of COX-2 expression by small interfering RNA (siRNA) in human gastric cancer cells and compared it to the effects of treatment with a specific COX-2 inhibitor. COX-2 mRNA and proteins were significantly reduced by up to 80% on day 2 after COX-2 siRNA transfection to the gastric cancer cell line MKN45. Concentrations of prostaglandins E2 (PGE2) in the condition medium were also reduced to 30% after siRNA transfection. Transfection of COX-2 siRNA exhibited a more potent anti-proliferative effect on MKN45 cells than treatment with high-dose (100 microM) NS398. COX-2 siRNA also significantly reduced tumor growth in nude mice. While COX-2 siRNA transfection alone had no obvious pro-apoptotic effects, unlike low-dose (10 microM) NS398 it enhanced the apoptotic reaction of MKN45 cells to cisplatin therapy. In conclusion, our results demonstrate for the first time that COX-2 siRNA inhibits cell growth and enhances the chemosensitivity of gastric cancer cells. RNA interference may be a promising alternative to specific COX-2 inhibitors in the prevention and treatment of gastric cancer.