Over-expression of P-glycoprotein(P-gp),an ATP-dependent drug efflux pump,represents one of the major mechanisms that contribute to multidrug resistance(MDR) in cancer cells.This study examined the effects of troglita...Over-expression of P-glycoprotein(P-gp),an ATP-dependent drug efflux pump,represents one of the major mechanisms that contribute to multidrug resistance(MDR) in cancer cells.This study examined the effects of troglitazone,a ligand of peroxisome proliferator-activated receptor gamma(PPARγ),on P-gp-mediated MDR in SGC7901/VCR cells(a vincristine-resistant human gastric cancer cell line).The expression of P-gp was detected by RT-PCR and Western blotting,respectively.The SGC7901/VCR cells were treated with 0.1 mg/L vincristine(VCR) alone or in combination with 1,5,10 μmol/L troglitazone for 24 h.PPARγ was measured by electrophoretic mobility shift assay(EMSA).The intracellular concentration of Rhodamine123(Rh123,a fluorescent P-gp substrate) was assayed to evaluate the activity of P-gp.The cell cycle and apoptosis were measured by flow cytometry.The results showed that the P-gp was increasingly expressed in SGC7901,BGC823 and SGC7901/VCR cells in turn,suggesting that MDR in the SGC7901/VCR cells was mediated by the increased expression of P-gp.In the SGC7901/VCR cells,the expression level of total PPARγ was increased,however,the protein level and activity of PPARγ in the nuclei of cells decreased significantly.Troglitazone elevated the PPARγ activity in SGC7901/VCR cells in a dose-dependent manner.Troglitazone decreased the P-gp expression and markedly enhanced the accumulation of Rh123 in SGC7901/VCR cells in a dose-dependent manner.We also found that troglitazone significantly increased the percentage of SGC7901/VCR cells in the G2/M phase and decreased the cell percentage in G1 and S phase in a dose-dependent manner.Troglitazone significantly increased the apoptotic rate of SGC7901/VCR cells treated by VCR or ADR in a dose-dependent manner.It was concluded that P-gp-overexpressed SGC7901/VCR cells have minor endogenous PPARγ activity.Elevation of the PPARγ activity by troglitazone can reverse P-gp-mediated MDR via down-regulating the expression and activity of P-gp in SGC7901/VCR cells.It was suggested that troglitazone can dramatically enhance the sensitivity of P-gp-mediated MDR cancer cells to chemotherapeutic agents.展开更多
In order to investigate the regulatory role of connective tissue growth factor （CTGF） on production of RANTES （regulated on activation, normal T cell expressed and secreted） in rat glomerular mesangial cells, and ...In order to investigate the regulatory role of connective tissue growth factor （CTGF） on production of RANTES （regulated on activation, normal T cell expressed and secreted） in rat glomerular mesangial cells, and the modulatory effect of lipoxin A4（LXA4） on action of CTGF, and to explore the mechanisms of action of CTGF and LXA4, cultured rat mesangial cells were treated with CTGF, with or without preincubation with LXA4. Expression of mRNA was analyzed by RT-PCR. Protein of RANTES in the supernatants was determined by ELISA. Monocyte transmigration was assessed by in vitro chemotaxis assay. Expression of p42/44 mitogen-activated protein kinase （MAPK）, phosphoinositide 3-kinase （PI3-K） and protein kinase B （PKB） was assessed by Western blotting. DNA-binding activity of nuclear factor-κB （NF-κB） was determined by electrophoretic mobility shift assay （EMSA）. To observe whether transfection of LXA4 receptor homologue gene （LRHG） into mesangial cells intensified these modulatory effects of LXA4, mesangial cells were transfected with pcDNA3.1/LRHG vector. The results showed that CTGF enhanced the mRNA expression and protein release of RANTES, and the expression of phospho （P）-p42/44 MAPK, P-PI3-K, P-PKB and NF-κB. P-p42/44 MAPK blockade inhibited the CTGF-induced expression of P-p42/44 MAPK and partially decreased the level of RANTES in supernatants. P-PI3-K blockade downregulated the CTGF-stimulated expression of P-PI3-K, P-PKB and NF-κB, and partially decreased the release of RANTES. NF-κB blockade abrogated the CTGF-activated NF-κB and partially decreased the secretion of RANTES. LXA4 dose-dependently inhibited the CTGF-stimulated above action. Transfection of LRHG into mesangial cells intensified these inhibitory effects of LXA4 on CTGF-induced release of RANTES and expression of the P-p42/44 MAPK. In conclusion, LXA4 inhibits CTGF-induced production of RANTES via PI3-K/PKB/NF-κB and p42/44 MAPK-dependent signal pathway, which is mediated by LRHG in rat mesangial cells.展开更多
AIM:To investigate lipopolysaccharide(LPS) related signal transduction in interstitial cells of Cajal(ICCs) from mouse small intestine.METHODS:For this study,primary culture of ICCs was prepared from the small intesti...AIM:To investigate lipopolysaccharide(LPS) related signal transduction in interstitial cells of Cajal(ICCs) from mouse small intestine.METHODS:For this study,primary culture of ICCs was prepared from the small intestine of the mouse.LPS was treated to the cells prior to measurement of the membrane currents by using whole-cell patch clamp technique.Immunocytochemistry was used to examine the expression of the proteins in ICCs.RESULTS:LPS suppressed the pacemaker currents of ICCs and this could be blocked by AH6809,a prostaglandin E2-EP2 receptor antagonist or NG-Nitro-Larginine Methyl Ester,an inhibitor of nitric oxide(NO) synthase.Toll-like receptor 4,inducible NO synthase or cyclooxygenase-2 immunoreactivity by specific antibodies was detected on ICCs.Catalase(antioxidant agent) had no action on LPS-induced action in ICCs.LPS actions were blocked by nuclear factor kB(NF-kB) inhibitor,actinomycin D(a gene transcription inhibitor),PD 98059(a p42/44 mitogen-activated protein kinases inhibitor) or SB 203580 [a p38 mitogen-activated protein kinases(MAPK) inhibitor].SB 203580 also blocked the prostaglandin E2-induced action on pacemaker currents in ICCs but not NO.CONCLUSION:LPS inhibit the pacemaker currents in ICCs via prostaglandin E2-and NO-dependent mechanism through toll-like receptor 4 and suggest that MAPK and NF-kB are implicated in these actions.展开更多
:AIM To construct Hsp90 antisense RNAeukaryotic expression vector, transfect it intoSGC7901 and SGC7901/VCR of MDR-type humangastric cancer cell lines, HCC7402 of humanhepatic cancer and Eel09 of human esophagealcance...:AIM To construct Hsp90 antisense RNAeukaryotic expression vector, transfect it intoSGC7901 and SGC7901/VCR of MDR-type humangastric cancer cell lines, HCC7402 of humanhepatic cancer and Eel09 of human esophagealcancer cell lines, and to study the cell cycledistribution of the gene transected cells andtheir response to chemotherapeutic drugs.METHODS A I .03kb cDNA sequence of Hsp90Pwas obtained from the primary plasmid phHsp90by EcoR 1 and BamH I nuclease digestion andwas cloned to the EcoR 1 and BamH 1 site ofthe pcDNA by T4DNA ligase and an antisenseorientation of Hsp900 expression vector wasconstructed. The constructs were transfectedwith lipofectamine and positive clones wereselected with G418. The expression of RNA wasdetermined with dot blotting and RNaseprotection assay, and the expression of Hsp90protein determined with Western blot. Cell cycledistribution of the transfectants was analyzedwith flow cytometry, and the drug sensitivity ofthe transfectants to adriamycin (ADR ),vincrinstine (VCR ), mitomycin (MMC ) andcyclophosphamide (CTX ) with MTT andintracellular drug concentration of thetransfectants was determined with flowcytometry.RESULTS In EcoR 1 and BamH I restrictionanalysis, the size and the direction of the clonedsequence of Hsp900 remained what had beendesigned and the gene constructs were namedpcDNA-Hsp90. AH^SGC7901, AH^SGC7901/ VCR,AH-HCC7402 and AH-Eel09 cell clones allexpressed Hsp90 anti--sense RNA. Theexpression of Hsp90 was down--regulated in AHSGC7901, AH--SGC7901/ VCR, AH-HCC7402 andAH--Eel09 cell clones. Cell cycle distribution waschanged differently. In AH-SGC7901/ VCR andAH-Ec109 cells, G, phase cells were increased; Sphase and G, phase cells were decreased ascompared with their parental cell lines. In AHSGC7901 cell, G, phase cells were decreased, Qphase cells increased and S phase cells were notchanged, and in AH-HCC7402 cells G,, S and qphase cells remained unchanged as comparedwith their parental cell lines. The sensitivity ofAH--SGC7901, AH--SGC7901/ VCR, AH-HCC7402 andAH-Ec109 to chemotherapeutic drugs, thesensitivity ot AH--SGC7901/ VCR to ADR, VCR,MMC and CTX the sensitivity of AH-HCC7402 toADR and VCR, and the sensitivity of Eel09 toADR, VCR and CTX all increased as comparedwith their parental cell lines. The meanfluorescence intensity of ADR in AH--SGC7901,AH-SGC7901/ VCR, AH--HCC7402 and AH-Ec109was also significantly elevated (P< 0. 05).CONCLUSION Down-regulation of HsP90 couldchange cell cycle distribution and increase thedrug sensitivity of tumor cells.展开更多
AIM In this study we investigated therelationship of the X protein of HBV and nuclearfactor-KB (NF-κB) and the expression of NF-KB inhuman hepatocellular carcinoma tissues.METHODS Immunohistochemistry SP methodwas us...AIM In this study we investigated therelationship of the X protein of HBV and nuclearfactor-KB (NF-κB) and the expression of NF-KB inhuman hepatocellular carcinoma tissues.METHODS Immunohistochemistry SP methodwas used to detect the expression of NF-κB and the X protein of HBV in human hepatocellularcarcinoma tissues of 52 cases. Gene transfectionmediated by lipofectamine was used to transfectthe eukaryotic expression vector pCDNA3. 1-HBXof HBV x gene into human hepatocellularcarcinoma cell line HCC-9204 and NF-κB wasdetected.RESULTS NF-κB was widely expressed inhuman hepatocellular carcinoma tissues in atotal of 52 cases and its expression was relatedto the X protein of HBV. NF-KB was localizedboth in the cytoplasm and . The nuclei ofhepatocellular carcinoma cells in 11 cases whichwere positive for the X protein of HBV while in 41cases negative for the X protein of HBV, NF-Kbwas only localized in the cytoplasm ofhepatocellular carcinoma cells but translocatedto the nuclei of hepatocellular carcinoma cellsafter the eukaryotic expression vectorpCDNA3.1-HBX was transfected into HCC-9204cells.CONCLUSION This study strongly suggeststhat the nuclear factor NF-KB is widely expressedin hepatocellular carcinoma tissues in differentstyles according to the expression of the Xprotein of HBV. NF-κB is abnormally activated inhepatocellular carcinoma, which is probablyrelated to the X protein of HBV. The X protein ofHBV can activate NF-κB to translocate into nucleiof hepatocellular carcinoma cells.展开更多
O6-methylguanine DNA methyltransferase(MGMT) can remove DNA alkylation adducts, thereby repairing damaged DNA and contributing to the drug resistance of gliomas to alkylating agents. In addition, glioma stem-like cell...O6-methylguanine DNA methyltransferase(MGMT) can remove DNA alkylation adducts, thereby repairing damaged DNA and contributing to the drug resistance of gliomas to alkylating agents. In addition, glioma stem-like cells(GSCs) have been demonstrated to be involved in the recurrence and treatment resistance of gliomas. In this study, we aimed to investigate MGMT expression and regulatory mechanisms in GSCs and the association of MGMT with temozolomide(TMZ) sensitivity. GSCs were enriched from one MGMT-positive cell line(SF-767) and 7 MGMT-negative cell lines(U251, SKMG-4, SKMG-1, SF295, U87, MGR1, and MGR2) through serum-free clone culture. GSCs from the U251G, SKMG-4G, SF295G, and SKMG-1G cell lines became MGMT-positive, but those from the U87G, MGR1G, and MGR2G cell lines remained MGMT-negative. However, all the GSCs and their parental glioma cell lines were positive for nuclear factor-κB(NF-κB). In addition, GSCs were more resistant to TMZ than their parental glioma cell lines(P < 0.05). However, there was no significant difference in the 50% inhibition concentration(IC50) of TMZ between MGMT-positive and MGMT-negative GSCs(P > 0.05). When we treated the MGMT-positive GSCs with TMZ plus MG-132(an NF-κB inhibitor), the antitumor activity was significantly enhanced compared to that of GSCs treated with TMZ alone(P < 0.05). Furthermore, we found that MGMT expression decreased through the down-regulation of NF-κB expression by MG-132. Our results show that MG-132 may inhibit NF-κB expression and further decrease MGMT expression, resulting in a synergistic effect on MGMT-positive GSCs. These results indicate that enhanced MGMT expression contributes to TMZ resistance in MGMT-positive GSCs.展开更多
Objective: To explore the effect of gamma irradiation on nuclear factor-kappa B in cultured bone marrow stromal cells. Methods: Immunocytochemistry, Western blot and electrophoretic mobility shift assay(EMSA) were use...Objective: To explore the effect of gamma irradiation on nuclear factor-kappa B in cultured bone marrow stromal cells. Methods: Immunocytochemistry, Western blot and electrophoretic mobility shift assay(EMSA) were used. Results: The expression of NF-κB in cultured mouse bone marrow stromal cells (BMSCs) on the level of protein was elevated after exposure to 60Co in the dosage of 8. 0 Gy with the use of immunocytochemistry and Western blot. The activity of nuclear factor-kappa B in cultured BMSCs was significantly increased after exposure to gamma irradiation by using EMSA. The activity peak was at the 4th h after irradiation. Conclusion: Our results suggest that the activation of nuclear factor-kappa B in the BMSCs after irradiation may be involved in the protection of BMSCs against apoptosis and in the recovery of hematopoiesis after radiation.展开更多
基金supported by grants from Natural Sciences Foundation of Hubei Province (No.2007ABA065)Science and Technology Key Project of Health Bureau of Hubei Province (No.JX1B006)
文摘Over-expression of P-glycoprotein(P-gp),an ATP-dependent drug efflux pump,represents one of the major mechanisms that contribute to multidrug resistance(MDR) in cancer cells.This study examined the effects of troglitazone,a ligand of peroxisome proliferator-activated receptor gamma(PPARγ),on P-gp-mediated MDR in SGC7901/VCR cells(a vincristine-resistant human gastric cancer cell line).The expression of P-gp was detected by RT-PCR and Western blotting,respectively.The SGC7901/VCR cells were treated with 0.1 mg/L vincristine(VCR) alone or in combination with 1,5,10 μmol/L troglitazone for 24 h.PPARγ was measured by electrophoretic mobility shift assay(EMSA).The intracellular concentration of Rhodamine123(Rh123,a fluorescent P-gp substrate) was assayed to evaluate the activity of P-gp.The cell cycle and apoptosis were measured by flow cytometry.The results showed that the P-gp was increasingly expressed in SGC7901,BGC823 and SGC7901/VCR cells in turn,suggesting that MDR in the SGC7901/VCR cells was mediated by the increased expression of P-gp.In the SGC7901/VCR cells,the expression level of total PPARγ was increased,however,the protein level and activity of PPARγ in the nuclei of cells decreased significantly.Troglitazone elevated the PPARγ activity in SGC7901/VCR cells in a dose-dependent manner.Troglitazone decreased the P-gp expression and markedly enhanced the accumulation of Rh123 in SGC7901/VCR cells in a dose-dependent manner.We also found that troglitazone significantly increased the percentage of SGC7901/VCR cells in the G2/M phase and decreased the cell percentage in G1 and S phase in a dose-dependent manner.Troglitazone significantly increased the apoptotic rate of SGC7901/VCR cells treated by VCR or ADR in a dose-dependent manner.It was concluded that P-gp-overexpressed SGC7901/VCR cells have minor endogenous PPARγ activity.Elevation of the PPARγ activity by troglitazone can reverse P-gp-mediated MDR via down-regulating the expression and activity of P-gp in SGC7901/VCR cells.It was suggested that troglitazone can dramatically enhance the sensitivity of P-gp-mediated MDR cancer cells to chemotherapeutic agents.
文摘In order to investigate the regulatory role of connective tissue growth factor （CTGF） on production of RANTES （regulated on activation, normal T cell expressed and secreted） in rat glomerular mesangial cells, and the modulatory effect of lipoxin A4（LXA4） on action of CTGF, and to explore the mechanisms of action of CTGF and LXA4, cultured rat mesangial cells were treated with CTGF, with or without preincubation with LXA4. Expression of mRNA was analyzed by RT-PCR. Protein of RANTES in the supernatants was determined by ELISA. Monocyte transmigration was assessed by in vitro chemotaxis assay. Expression of p42/44 mitogen-activated protein kinase （MAPK）, phosphoinositide 3-kinase （PI3-K） and protein kinase B （PKB） was assessed by Western blotting. DNA-binding activity of nuclear factor-κB （NF-κB） was determined by electrophoretic mobility shift assay （EMSA）. To observe whether transfection of LXA4 receptor homologue gene （LRHG） into mesangial cells intensified these modulatory effects of LXA4, mesangial cells were transfected with pcDNA3.1/LRHG vector. The results showed that CTGF enhanced the mRNA expression and protein release of RANTES, and the expression of phospho （P）-p42/44 MAPK, P-PI3-K, P-PKB and NF-κB. P-p42/44 MAPK blockade inhibited the CTGF-induced expression of P-p42/44 MAPK and partially decreased the level of RANTES in supernatants. P-PI3-K blockade downregulated the CTGF-stimulated expression of P-PI3-K, P-PKB and NF-κB, and partially decreased the release of RANTES. NF-κB blockade abrogated the CTGF-activated NF-κB and partially decreased the secretion of RANTES. LXA4 dose-dependently inhibited the CTGF-stimulated above action. Transfection of LRHG into mesangial cells intensified these inhibitory effects of LXA4 on CTGF-induced release of RANTES and expression of the P-p42/44 MAPK. In conclusion, LXA4 inhibits CTGF-induced production of RANTES via PI3-K/PKB/NF-κB and p42/44 MAPK-dependent signal pathway, which is mediated by LRHG in rat mesangial cells.
基金Supported by Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Education,Science and Technology,No.2012-0001335
文摘AIM:To investigate lipopolysaccharide(LPS) related signal transduction in interstitial cells of Cajal(ICCs) from mouse small intestine.METHODS:For this study,primary culture of ICCs was prepared from the small intestine of the mouse.LPS was treated to the cells prior to measurement of the membrane currents by using whole-cell patch clamp technique.Immunocytochemistry was used to examine the expression of the proteins in ICCs.RESULTS:LPS suppressed the pacemaker currents of ICCs and this could be blocked by AH6809,a prostaglandin E2-EP2 receptor antagonist or NG-Nitro-Larginine Methyl Ester,an inhibitor of nitric oxide(NO) synthase.Toll-like receptor 4,inducible NO synthase or cyclooxygenase-2 immunoreactivity by specific antibodies was detected on ICCs.Catalase(antioxidant agent) had no action on LPS-induced action in ICCs.LPS actions were blocked by nuclear factor kB(NF-kB) inhibitor,actinomycin D(a gene transcription inhibitor),PD 98059(a p42/44 mitogen-activated protein kinases inhibitor) or SB 203580 [a p38 mitogen-activated protein kinases(MAPK) inhibitor].SB 203580 also blocked the prostaglandin E2-induced action on pacemaker currents in ICCs but not NO.CONCLUSION:LPS inhibit the pacemaker currents in ICCs via prostaglandin E2-and NO-dependent mechanism through toll-like receptor 4 and suggest that MAPK and NF-kB are implicated in these actions.
基金Project supported by the National Natural Science Foundation of China,No.39570806National Excel1ent Youth Scientific Foundation,No.3952020.
文摘:AIM To construct Hsp90 antisense RNAeukaryotic expression vector, transfect it intoSGC7901 and SGC7901/VCR of MDR-type humangastric cancer cell lines, HCC7402 of humanhepatic cancer and Eel09 of human esophagealcancer cell lines, and to study the cell cycledistribution of the gene transected cells andtheir response to chemotherapeutic drugs.METHODS A I .03kb cDNA sequence of Hsp90Pwas obtained from the primary plasmid phHsp90by EcoR 1 and BamH I nuclease digestion andwas cloned to the EcoR 1 and BamH 1 site ofthe pcDNA by T4DNA ligase and an antisenseorientation of Hsp900 expression vector wasconstructed. The constructs were transfectedwith lipofectamine and positive clones wereselected with G418. The expression of RNA wasdetermined with dot blotting and RNaseprotection assay, and the expression of Hsp90protein determined with Western blot. Cell cycledistribution of the transfectants was analyzedwith flow cytometry, and the drug sensitivity ofthe transfectants to adriamycin (ADR ),vincrinstine (VCR ), mitomycin (MMC ) andcyclophosphamide (CTX ) with MTT andintracellular drug concentration of thetransfectants was determined with flowcytometry.RESULTS In EcoR 1 and BamH I restrictionanalysis, the size and the direction of the clonedsequence of Hsp900 remained what had beendesigned and the gene constructs were namedpcDNA-Hsp90. AH^SGC7901, AH^SGC7901/ VCR,AH-HCC7402 and AH-Eel09 cell clones allexpressed Hsp90 anti--sense RNA. Theexpression of Hsp90 was down--regulated in AHSGC7901, AH--SGC7901/ VCR, AH-HCC7402 andAH--Eel09 cell clones. Cell cycle distribution waschanged differently. In AH-SGC7901/ VCR andAH-Ec109 cells, G, phase cells were increased; Sphase and G, phase cells were decreased ascompared with their parental cell lines. In AHSGC7901 cell, G, phase cells were decreased, Qphase cells increased and S phase cells were notchanged, and in AH-HCC7402 cells G,, S and qphase cells remained unchanged as comparedwith their parental cell lines. The sensitivity ofAH--SGC7901, AH--SGC7901/ VCR, AH-HCC7402 andAH-Ec109 to chemotherapeutic drugs, thesensitivity ot AH--SGC7901/ VCR to ADR, VCR,MMC and CTX the sensitivity of AH-HCC7402 toADR and VCR, and the sensitivity of Eel09 toADR, VCR and CTX all increased as comparedwith their parental cell lines. The meanfluorescence intensity of ADR in AH--SGC7901,AH-SGC7901/ VCR, AH--HCC7402 and AH-Ec109was also significantly elevated (P< 0. 05).CONCLUSION Down-regulation of HsP90 couldchange cell cycle distribution and increase thedrug sensitivity of tumor cells.
文摘AIM In this study we investigated therelationship of the X protein of HBV and nuclearfactor-KB (NF-κB) and the expression of NF-KB inhuman hepatocellular carcinoma tissues.METHODS Immunohistochemistry SP methodwas used to detect the expression of NF-κB and the X protein of HBV in human hepatocellularcarcinoma tissues of 52 cases. Gene transfectionmediated by lipofectamine was used to transfectthe eukaryotic expression vector pCDNA3. 1-HBXof HBV x gene into human hepatocellularcarcinoma cell line HCC-9204 and NF-κB wasdetected.RESULTS NF-κB was widely expressed inhuman hepatocellular carcinoma tissues in atotal of 52 cases and its expression was relatedto the X protein of HBV. NF-KB was localizedboth in the cytoplasm and . The nuclei ofhepatocellular carcinoma cells in 11 cases whichwere positive for the X protein of HBV while in 41cases negative for the X protein of HBV, NF-Kbwas only localized in the cytoplasm ofhepatocellular carcinoma cells but translocatedto the nuclei of hepatocellular carcinoma cellsafter the eukaryotic expression vectorpCDNA3.1-HBX was transfected into HCC-9204cells.CONCLUSION This study strongly suggeststhat the nuclear factor NF-KB is widely expressedin hepatocellular carcinoma tissues in differentstyles according to the expression of the Xprotein of HBV. NF-κB is abnormally activated inhepatocellular carcinoma, which is probablyrelated to the X protein of HBV. The X protein ofHBV can activate NF-κB to translocate into nucleiof hepatocellular carcinoma cells.
基金supported by the National Natural Science Foundation of China(No.30772551)the Science &Technology Program of Guangdong Province(No.2011B031800178)+1 种基金National High-technology Research and Development Program of China(No.2012AA02A508)Specialized Research Fund for the Doctoral Program of Higher Education(No.20110171110076)
文摘O6-methylguanine DNA methyltransferase(MGMT) can remove DNA alkylation adducts, thereby repairing damaged DNA and contributing to the drug resistance of gliomas to alkylating agents. In addition, glioma stem-like cells(GSCs) have been demonstrated to be involved in the recurrence and treatment resistance of gliomas. In this study, we aimed to investigate MGMT expression and regulatory mechanisms in GSCs and the association of MGMT with temozolomide(TMZ) sensitivity. GSCs were enriched from one MGMT-positive cell line(SF-767) and 7 MGMT-negative cell lines(U251, SKMG-4, SKMG-1, SF295, U87, MGR1, and MGR2) through serum-free clone culture. GSCs from the U251G, SKMG-4G, SF295G, and SKMG-1G cell lines became MGMT-positive, but those from the U87G, MGR1G, and MGR2G cell lines remained MGMT-negative. However, all the GSCs and their parental glioma cell lines were positive for nuclear factor-κB(NF-κB). In addition, GSCs were more resistant to TMZ than their parental glioma cell lines(P < 0.05). However, there was no significant difference in the 50% inhibition concentration(IC50) of TMZ between MGMT-positive and MGMT-negative GSCs(P > 0.05). When we treated the MGMT-positive GSCs with TMZ plus MG-132(an NF-κB inhibitor), the antitumor activity was significantly enhanced compared to that of GSCs treated with TMZ alone(P < 0.05). Furthermore, we found that MGMT expression decreased through the down-regulation of NF-κB expression by MG-132. Our results show that MG-132 may inhibit NF-κB expression and further decrease MGMT expression, resulting in a synergistic effect on MGMT-positive GSCs. These results indicate that enhanced MGMT expression contributes to TMZ resistance in MGMT-positive GSCs.
基金Supported by the "Ninth Five" Obligatory Budget of PLA. No. 96L045
文摘Objective: To explore the effect of gamma irradiation on nuclear factor-kappa B in cultured bone marrow stromal cells. Methods: Immunocytochemistry, Western blot and electrophoretic mobility shift assay(EMSA) were used. Results: The expression of NF-κB in cultured mouse bone marrow stromal cells (BMSCs) on the level of protein was elevated after exposure to 60Co in the dosage of 8. 0 Gy with the use of immunocytochemistry and Western blot. The activity of nuclear factor-kappa B in cultured BMSCs was significantly increased after exposure to gamma irradiation by using EMSA. The activity peak was at the 4th h after irradiation. Conclusion: Our results suggest that the activation of nuclear factor-kappa B in the BMSCs after irradiation may be involved in the protection of BMSCs against apoptosis and in the recovery of hematopoiesis after radiation.
