Drug Resistance Of Gastric Cancer Cells Research Articles

Rosiglitazone Reverses Mitomycin C Resistance in Human Gastric Cancer Cells

IntroductionTo explore the mechanisms of rosiglitazone (ROS), a selective peroxisome proliferator-activated receptor gamma ligand, in reversing mitomycin C (MMC) resistance in a human drug-resistant gastric cancer cell line. MethodsThe vincristine-resistant human gastric cancer cell line SGC7901/VCR and its parental cell line SGC7901 were treated with ROS, MMC (negative control), cyclosporine A+MMC (positive control) or ROS+MMC. A tetrazolium blue (methyl thiazolyl tetrazolium) assay was used to evaluate the sensitivity to these treatments. Flow cytometry analysis and acridine orange-ethidium bromide (AO-EB) fluorescent staining were used to determine the effects of ROS on MMC-induced apoptosis. Reverse transcription polymerase chain reaction and western blotting were used to measure the expression of multidrug resistant 1 (MDR1), Livin and P-glycoprotein (P-gp). ResultsROS administration dose dependently increased the reversal index in MMC-treated SCG7901/VCR cells. ROS increased apoptosis in SGC7901/VCR cells compared with the blank group and MMC group. ROS+MMC also increased apoptosis in SGC7901/VCR cells compared with other groups (P < 0.05 or P < 0.01). The mRNA expression of MDR1 and Livin and the protein expression of P-gp in SGC7901/VCR cells were significantly higher than those in SGC7901 cells (P < 0.01). However, ROS or ROS+MMC treatment markedly upregulated the mRNA expression of MDR1 and Livin and the protein expression of P-gp in SGC7901/VCR cells (P < 0.01). ConclusionsROS reverses MMC resistance in human gastric cancer SGC7901/VCR cells by reducing expression of MDR1, Livin and P-gp and increasing apoptosis.

Inhibition of activated Stat3 reverses drug resistance to chemotherapeutic agents in gastric cancer cells

Multidrug resistance is a major obstacle in the treatment of gastric cancer. The underlying mechanisms of this phenomenon have not been well understood. Accumulating evidence indicates that Stat3 plays an important role in tumorigenesis of various primary cancers and cancer cell lines by upregulating cell survival proteins and downregulating tumor suppressors. We propose that the Stat3 pathway is also involved in acquired drug resistance of gastric cancer. To test this hypothesis, we investigated the expression and activation of Stat3 in drug resistant gastric cancer cell lines. Western blotting and real-time reverse transcription-PCR determined that Stat3 and its target genes were overactivated and/or overexpressed in drug resistant cells. Inhibition of Stat3 function resulted in significant decreases in cisplatin resistance and enhanced apoptosis in drug resistant cells. The levels of Stat3 target oncogenes such as Bcl-2 and c-Myc were decreased with DPP, a Stat3 inhibitor, treatment, while the expression of tumor suppressor p53 was increased. Interestingly, the vacuolar ATPase, a proton pump which interferes the uptake of therapeutic drugs, was down regulated by Stat3 inhibition. In conclusion, these data supported the hypothesis that interruption of Stat3 signaling could reverse resistance to chemotherapy agents in human gastric cancer cells.

A FGFR2 inhibitor, Ki23057, enhances the chemosensitivity of drug-resistant gastric cancer cells

AimThe aim of this study was to clarify the ability of a FGFR2 inhibitor, Ki23057, to enhance the chemosensitivity of drug-resistant gastric cancer cell lines when used in combination with chemotherapeutic drugs. Materials and methodsFive cancer cell lines resistant to irinotecan (SN38), paclitaxel (PTX), etoposide (VP16), oxaliplatin (OXA), and gemcitabine (GEM) were respectively established from a parent gastric cancer cell line, OCUM-2M, and were named OCUM-2M/SN38, OCUM-2M/PTX, OCUM-2M/VP16, OCUM-2M/OXA, and OCUM-2M/GEM. The effects of the combination of Ki23057 with anticancer drugs on proliferation, apoptosis, and mRNA expression were examined. ResultsKi23057 significantly decreased the IC50 values of OCUM-2M/SN38, OCUM-2M/PTX, and OCUM-2M/VP16, but not those of OCUM-2M/OXA and OCUM-2M/GEM. Ki23057 significantly enhanced the apoptosis rates induced by chemotherapeutic drugs in both the drug-resistant cell lines and the parental cell line. Ki23057 decreased the ERCC1 expression level in OCUM-2M/SN38, OCUM-2M/PTX, and OCUM-2M/VP16. Ki23057 increased the p53 expression level in OCUM-2M/SN38 and OCUM-2M/PTX, but not in OCUM-2M/VP16. ConclusionThe FGFR2 inhibitor Ki23057 might be therapeutically promising for treating drug-resistant gastric cancer cells, especially when used in combination with SN38, PTX, or VP16. The apoptosis process might be the main mechanism underlying the synergistic effect of these combinations. The ERCC1 and p53 genes may play an integral role in the synergism between Ki23057 and chemotherapeutic agents in drug-resistant cell lines.

Mad2β, an alternative variant of Mad2 reducing mitotic arrest and apoptosis induced by adriamycin in gastric cancer cells

Mad2β is an alternative splicing variant of spindle checkpoint gene mad2, which was previously found by us and was related to the drug resistance in gastric cancer cells. In this paper, we explored the molecular mechanisms that Mad2β variant promoted the formation of multidrug resistance in gastric cancer cells. We found that Mad2β variant was detected only in the two human drug resistant gastric cancer cell sublines SGC7901/VCR and SGC7901/ADR, and it did not appear in its parental cell line SGC7901 and other detected gastric cancer cell lines. Expressions of Mad2 mRNA and protein in SGC7901 cells transfected with Mad2β, SGC7901/VCR and SGC7901/ADR were significantly lower than that in SGC7901 cells. Moreover, SGC7901 cells overexpressing Mad2β variant became more resistant to adriamycin, vincristine and mitomycin by abrogating mitotic arrest and apoptosis. This suggests that expression of Mad2β variant decreases the relative expression of efficient MAD2, which may help gastric cancer cells to develop the phenotype of multidrug resistance.

Reversal of multidrug resistance in drug-resistant human gastric cancer cell line SGC7901/VCR by antiprogestin drug mifepristone.

To explore the reversal effect of mifepristone on multidrug resistance (MDR) in drug-resistant human gastric cancer cell line SGC7901/VCR and its mechanisms. Expression of multidrug resistance-associated protein(MRP) was detected using reverse transcription-polymerase chain reaction(RT-PCR). Flow cytometry was used to assay the expression of P-glycoprotein(P-gp), Bcl-2, Bax, and the mean fluorescent intensity of intracellular rhodamine 123 in the cells. Meanwhile, the protein levels of Bcl-2 and Bax were also detected by Western blotting analysis. The sensitivity of cells to the anticancer agent, vincrimycin(VCR), and the intracellular [(3) H]VCR accumulation were determined by tetrazolium blue (MTT) assay and a liquid scintillation counter, respectively. Expression of MRP and P-gp in SGC7901/VCR cells was 6.04-and 8.37-fold higher as compared with its parental SGC7901 cells, respectively. After treatment with 1, 5, 10, and 20 micromol/L mifepristone, SGC7901/VCR cells showed a 1.34-, 2.29-, 3.11-, and 3.71-fold increase in the accumulation of intracellular VCR, a known substrate of MRP, and a 1.03-, 2.04-, 3.08-, and 3.68-fold increase in the retention of rhodamine 123, an indicator of P-gp function, respectively. MTT assay revealed that the resistance of SGC7901/VCR cells to VCR was 11.96-fold higher than that of its parental cells. The chemosensitivity of SGC7901/VCR cells to VCR was enhanced by 1.02-, 7.19-, 12.84-, and 21.17-fold after treatment with mifepristone at above-mentioned dose. After 96 h of incubation with mifepristone 10 micromol/L, a concentration close to plasma concentrations achievable in human, the expression of Bcl-2 protein was decreased to (9.21+/-0.65)% from (25.32+/-1.44)%, whereas the expression of Bax protein was increased to (19.69+/-1.13)% from (1.24+/-0.78)% (P<0.01). Additionally, the effects of mifepristone on the expression of Bcl-2 and Bax proteins in SGC7901/VCR cells were further demonstrated by Western blotting analysis. Mifepristone has potent reversal effect on MDR in SGC7901/VCR via inhibiting the function of MRP and P-gp, modulating the expression of Bcl-2 and Bax proteins, and enhancing the sensitivity to anticancer agent VCR.

Effect of ZNRD1 gene antisense RNA on drug resistant gastric cancer cells.

To investigate the expression level of ZNRD1 gene in gastric cancer cells SGC7901 and gastric cancer MDR (multidrug resistant) cells SGC7901/VCR, and to observe the drug sensitizing and proliferation effect of ZNRD1 antisense nucleic acid transduction on SGC7901/VCR cells. Amplification of sequences encoding ZNRD1 from SGC7901/VCR cDNA by PCR. The levels of ZNRD1 mRNA expression were demonstrated using semiquantitative reverse transcription polymerase chain reaction (RT-PCR). Eukaryotic expression vector pcDNA3.1-anti ZNRD1 was constructed and transfected into SGC7901/VCR cells by lipofectamine. Immunochemical method was used to detect the expression of protein in SGC7901/VCR cells and transfectants. The cell cycle alteration and the intracellular adriamycin (ADM) accumulation were observed by FACS. Growth curve and drug sensitization of cells for vincristine (VCR) were analyzed with MTT assay. We cloned the open reading frame of full-length ZNRD1. The expression of ZNRD1 showed higher in SGC7901/VCR than in SGC7901 cells. The antisense ZNRD1 drug-resistant clones were selected after gene transfection. Immunochemical results showed that the expression level of ZNRD1 protein was lower in anti ZNRD1-SGC7901/VCR cells than that in non-transfectants. Comparing to SGC7901/VCR and pcDNA3.1-SGC7901/VCR, anti ZNRD1-SGC7901/VCR showed gradually accumulated in G(1) phase, with a concomitant decrease of cell population in S phase. FACS also suggested intracellular ADM accumulation increased 2fold in SGC7901/VCR cells after transfected with antisense ZNRD1. MTT assay showed that transfectants cells proliferation was lagged and more sensitive to VCR than non-transfectants. ZNRD1 gene displayed highly expression in VCR resistant gastric cancer cells. Expression of ZNRD1 protein was effectively blocked in anti ZNRD1-SGC7901/VCR cells by gene transfection. ZNRD1 antisense nucleic acid transfection sensitized drug resistant gastric cancer cells to VCR, increased ADM accumulation and inhibited the cells proliferation. ZNRD1 antisense RNA transduction could reverse the MDR of human drug-resistant gastric cancer cell SGC7901/VCR to a degree.

Transforming growth factor-beta and response to anticancer therapies in human liver and gastric tumors in vitro and in vivo.

Liver cancer and gastric cancer are the most common solid tumors worldwide. Transforming growth factor-beta (TGF-beta) production and lack of response to TGF-beta growth inhibitory effects have been associated with tumor progression and therapeutic resistance. HepG2, Hep3B, and SK-HEP-1 human liver cancer lines produce 3, 5.7, and 2.5 ng TGF-beta1; 1.4, 2, and 4 ng TGF-beta2 and 0.15, 0.2 and 0.22 ng TGF-beta3 per 107 cells (24 h). Expression of the TGF-beta type I receptor is 20x, 1x, and 0.6x the level in mink lung MvLu1 cells in the HepG2, Hep3B, and SK-HEP-1 cells, respectively. HepG2 and Hep3B cells do not express the TGF-beta type II receptor while SK-HEP-1 cells express 7x the level found in mink lung MvLu1 cells. Hs 746T, KATO III, RF-1, and RF-48 human gastric cancer cell lines produce 12. 5, 0.35, 0.4, and 0.4 ng TGF-beta1; 2.6, 0.95, 0.5, and 0.52 ng TGF-beta2 and 0.42, 0.17, 0.12, and 0.14 ng TGF-beta3 per 107 cells (24 h). Expression of TGF-beta type I receptor is 0.7x, 0.7x, 0.8x, 0.6x the level in mink lung MvLu1 cells in the Hs 746T, KATO III, RF-1 and RF-48 cells, respectively. KATO III cells are lacking in the TGF-beta type II receptor while Hs 746T, RF-1 and RF-48 cells express 10x, 0.8x, and 1x the levels in mink lung MvLu1 cells. The IC50 for TGF-beta1 is >>10 ng/ml in all of these lines except RF-48 where TGF-beta1 is mitogenic. The response of the cell lines to radiation, doxorubicin, mitomycin C, cisplatin, 5-fluorouracil, methotrexate, and gemcitabine showed that SK-HEP-1 was the most drug resistant liver cancer cell line and KATO III was the most drug resistant gastric cancer cell line. Overall, there was no correlation between TGF-beta secretion in cell culture and sensitivity of the cells to anticancer agents. Increased TGF-beta1 levels were detectable in the plasma of nude mice bearing Hep3B and Hs 746T xenografts. Those tumors which secreted greater amounts of TGF-beta were more therapeutically resistant in vivo.

Suppression of P-gp induced multiple drug resistance in a drug resistant gastric cancer cell line by overexpression of Fas.

AIM:To observe the drug sensitizing effect and related mechanisms of fas gene transduction on human drug-resistant gastric cancer cell SGC7901/VCR (resistant to Vincristine).METHODS:The cell cycle alteration was observed by FACS. The sensitivity of gastric cancer cells to apoptosis was determined by in vitro apoptosis assay. The drug sensitization of cells to several anti-tumor drugs was observed by MTT assay. Immunochemical method was used to show expression of P-gp and Topo II in gastric cancer cells.RESULTS:Comparing to SGC7901 and pBK-SGC7901/VCR, fas-SGC7901/VCR showed decreasing G2 cells and increasing S cells, the G2 phase fraction of pBK-SGC7901/VCR was about 3.0 times that of fas -SGC7901/VCR but S phase fraction of fas -SGC7901/VCR was about 1.9 times that of pBK-SGC7901/VCR, indicating S phase arrest of fas-SGC7901/VCR. FACS also suggested apoptosis of fas-SGC7901/VCR.fas-SGC7901/VCR was more sensitive to apoptosis inducing agent VM-26 than pBK-SGC7901/VCR. MTT assay showed increased sensitization of fas-SGC7901/VCR to DDP, MMC and 5-FU, but same sensitization to VCR according to pBK-SGC7901/VCR. SGC7901, PBK-SGC7901/VCR and fas -SGC7901/VCR had positively stained Topo II equally. P-gp staining in pBK-SGC7901/VCR was stronger than in SGC7901, but there was little staining of P-gp in fas-SGC7901/VCR.CONCLUSION:fas gene transduction could reverse the MDR of human drug-resistant gastric cancer cell SGC7901/VCR to a degree, possibly because of higher sensitization to apoptosis and decreased expression of P-gp.

Transduction of Fas gene or Bcl-2 antisense RNA sensitizes cultured drug resistant gastric cancer cells to chemotherapeutic drugs.

AIM:To compare the expression level of Fas gene and Bcl-2 gene in gastric cancer cells SGC7901 and gastric cancer MDR (multidrug resistant) cells SGC7901/VCR,to transduce Fas cDNA and Bcl-2 antisense nucleic acid into SGC7901/VCR cells respectively, and to observe the expression of two genes in transfectants and non-transfectants as well as their drug sensitivity.METHODS:Eukaryotic expression vector pBK-Fas cDNA and pDOR-anti Bcl-2 were constructed and transfected into SGC7901/VCR cells by lipofectamine,respectively.Northern blot and Western blot were used to detect the expression of mRNA and protein in SGC7901/VCR and SGC7901 cells and transfectants, and drug sensitivity of transfectants for VCR, CDDP and 5-FU was analyzed with MTT assay.RESULTS:After gene transfection, 80 for Fas and 120 for antisense Bcl-2 drug-resistant clones were selected from 2 X10(5) cells, transfection rate being 0.04% and 0.06%. Two clones of SGC7901 Fas/VCR cells and SGC7901 anti Bcl-2/VCR cells were randomly selected for further incubation. Hybridization results showed that the expression level of Fas mRNA and protein in SGC7901/VCR cells was much lower,but that of Bcl-2 mRNA and protein was higher than that in SGC7901 cells. The expression of Fas mRNA and protein in SGC7901 Fas/VCR cells was higher,and of Bcl-2 mRNA and protein was lower in SGC7901 anti Bcl-2/VCR cells than that in non-transfectants. MTT assay showed that transfectants were more sensitive to VCR, CDDP, 5-FU than non-transfectants. CONCLUSION:Bcl-2 gene displayed high expression while Fas gene had low expression in drug resistant gastric cancer cells. Expression of Bcl-2 protein was effectively blocked in SGC7901 anti Bcl-2/VCR cells by gene transfection. In contrast, the expression of Fas mRNA and protein in SGC7901 Fas/VCR cells increased. Fas gene and Bcl-2 antisense nucleic acid transfection sensitized drug resistant gastric cancer cells to chemotherapeutic drugs. These results suggest cell apoptosis plays an important role in the mechanism of MDR, and enhancing apoptosis might reverse MDR.