Objective To investigate the effects of sodium selenite on telomerase activity, apoptosis and expression of TERT, c-myc and p53 in rat hepatocytes. Methods Selenium at doses of 2.5, 5.0, and 10 μmol/kg was given to S...Objective To investigate the effects of sodium selenite on telomerase activity, apoptosis and expression of TERT, c-myc and p53 in rat hepatocytes. Methods Selenium at doses of 2.5, 5.0, and 10 μmol/kg was given to SD rats by garage. In rat hepatocytes, telomerase activity was measured by the telomeric repeat amplification protocol （TRAP）, apoptosis was detected by flow cytometry, and expressions of telomerase reverse transcriptase （TERT）, c-myc and p53 were analyzed by reverse transcription-polymerase chain reaction （RT-PCR）. c-Myc and P53 proteins were detected by immunochemistry. Results Selenium at doses of 2.5, 5.0, and 10 μmol/kg significantly increased hepatocellular telomerase activity and induced apoptosis in a dose-dependent manner. Although selenium at doses of 2.5, 5.0, and 10 μmol/kg displayed no obvious enhancing effect on the TERT mRNA expression in rat hepatocytes （P〉0.05）, it significantly increased the c-myc mRNA and p53 mRNA expression at the dose of 10 μmol/kg （P〈0.05）. Selenium at doses of 5.0 and 10 μmol/kg obviously increased the content of P53 protein in rat hepatocytes, but only at the dose of 10 μmol/kg, it significantly promoted the value of c-Myc protein in them. Conclusion Selenium can slightly increase telomerase activity and TERT expression, and significantly induce apoptosis and over-expression of c-myc and p53 at relatively high doses. The beneficial effects of selenium on senescence and aging may be mediated by telomerase activation and expression of TERT, c-myc, and p53 in rat hepatocytes.展开更多
The discovery and application of environment-sensitive genic male sterile(EGMS) rice germplasm provide an easy method for hybrid rice breeding and have made great contributions to hybrid rice production. Typically, th...The discovery and application of environment-sensitive genic male sterile(EGMS) rice germplasm provide an easy method for hybrid rice breeding and have made great contributions to hybrid rice production. Typically, the photoperiod-and thermosensitive GMS(P/TGMS) lines utilized in two-line hybrid systems are male sterile under long day or/and high temperature but fertile under short day or/and low temperature conditions. However, Yannong S(Yn S), a reverse TGMS(rTGMS) line, is sterile under low temperature(<29℃) and fertile under high temperature(>29.5℃). Here, we report a genetic study on the rTGMS trait in Yn S. Interestingly, the F1 plants of the cross between Yn S and a cultivar, L422, were male sterile at 22℃ and completely fertile at 27℃. Moreover, the segregation ratio of fertile and sterile individuals in Yn S/L422 F2 populations changed from 1:3.05 to 2.95:1 when the ambient temperature increased, showing that the rTGMS trait exhibits semidominance in Yn S. We further found a locus on chromosome 10, termed RTMS10, which controls the rTGMS trait in Yn S. We then finely mapped RTMS10 to a ~68 kb interval between markers ID13116 and ID1318 by Yn S/L422 BC6 F2 populations. A near iso-genic line(NIL) NL1 from the BC6 F3 generation was developed and the pollen of NL1 became abnormal from the meiosis stage under low temperature. In summary, we identified an rTGMS locus, RTMS10, and provided co-segregated markers, which could help to accelerate molecular breeding of rTGMS lines and better understand the rTGMS trait in rice.展开更多
BACKGROUND： Numerous current studies have suggested that human telomerase reverse transcriptase （hTERT） gene has neuroprotective effects and can inhibit apoptosis induced by various cytotoxic stresses; however, the...BACKGROUND： Numerous current studies have suggested that human telomerase reverse transcriptase （hTERT） gene has neuroprotective effects and can inhibit apoptosis induced by various cytotoxic stresses; however, the mechanism of action remains unknown. OBJECTIVE： To evaluate the neuroprotective effects and possible mechanism of action of hTERT gene transfection in human embryonic cortical neurons treated with beta-amyloid fragment 25-35 （AI325-35）. DESIGN, TIME AND SETTING： The randomized, controlled and molecular biological studies were performed at the Department of Anatomy and Brain Research, Zhongshan School of Medicine, Sun Yat-sen University, China, from September 2005 to June 2008. MATERIALS： AdEasy-1 Expression System was gifted by Professor Guoquan Gao from Sun Yat-Sen University, China. Human cortical neurons were derived from 12-20 week old aborted fetuses, obtained from the Guangzhou Maternal and Child Health Hospital, China. Mouse anti-Odk5 and mouse anti-p16 monoclonal antibodies （Lab Vision, USA）, and mouse anti-hTERT monoclonal antibody （Epitomics, USA）, were used in this study. METHODS： （1） Recombinant adenovirus vectors, encoding hTERT （Ad-hTERT） and green fluorescent protein （Ad-GFP）, were constructed using the AdEasy-1 Expression System. Human embryonic cortical neurons in the Ad-hTERT group were transfected with Ad-hTERT for 1-21 days. Likewise, human embryonic cortical neurons in the Ad-GFP group were transfected with Ad-GFP for 1-21 days. Human embryonic cortical neurons in the control group were cultured as normal. （2） Human embryonic cortical neurons in the Ad-hTERT group were treated with 10 pmol/L Aβ25-35 for 24 hours. Normal human embryonic cortical neurons treated with 10 pmol/Lβ25.35 for 24 hours served as a model group. Human embryonic cortical neurons in the Ad-GFP and control groups were not treated with Aβ25-35. MAIN OUTCOME MEASURES： Expression of hTERT in human embryonic cortical neurons was evaluated by immunocytochemical staining and Western blot assay. Telomerase activity was measured using a PCR-based telomeric repeat amplification protocol （TRAP） ELISA kit. Neural activity in human embryonic cortical neurons was examined by MTT assay; apoptosis was measured using TUNEL assay; and Cdk5 and p16 protein expressions were measured by Western blot. RESULTS： Expression of hTERT protein was significantly increased and peaked at day 3 post-transfection in the Ad-hTERT group. No hTERT expression was detected in the Ad-GFP and control groups. Telomerase activity was significantly greater in the Ad-hTERT group compared with the Ad-GFP and control groups （P 〈 0.01）. Compared with the control group, cell activity was significantly decreased （P 〈 0.05）, and cell apoptotic rate, Cdk5 and p16 expression were significantly increased （P 〈 0.01） in the model group. Compared with the model group, cell activity was increased in the Ad-hTERT group, and peaked at day 3 post-transfection （P 〈 0.05）. Neuroprotective effects also peaked at day 3 post-transfection; and the apoptotic rate, Cdk5 and p16 expression significantly decreased （P 〈 0.01）. CONCLUSION： Expression of hTERT in human embryonic cortical neurons can relieve Aβ25-35-induced neuronal apoptosis. The possible mechanism by which hTERT produces these neuroprotective effects may be associated with inhibition of Cdk5 and p16 expression.展开更多
AIM： To evaluate the anti-HIV activity and mechanism of action of wikstroelide M, a daphnane diterpene from Daphne acutiloba Rehder （Thymelaeaceae）. METHOD： The anti-HIV activities of wikstroelide M against differ...AIM： To evaluate the anti-HIV activity and mechanism of action of wikstroelide M, a daphnane diterpene from Daphne acutiloba Rehder （Thymelaeaceae）. METHOD： The anti-HIV activities of wikstroelide M against different HIV strains were evaluated by cytopathic effect assay and p24 quantification assay with ELISA. The inhibitory effect of wikstroelide M on HIV reverse transcription was analyzed by real-time PCR and ELISA. The effect of wikstroelide M on HIV-1 integrase nuclear translocation was observed with a cell-based imaging assay. The effect of wikstroelide M on LEDGF/p75-IN interaction was assayed by molecular docking. RESULTS： Wikstroelide M potently inhibited different HIV-1 strains, including HIV-lmn, HIV-1AI7, and HIV-19495, induced a cytopathic effect, with ECs0 values ranging from 3.81 to 15.65 ng.mL-I. Wikstroelide M also had high inhibitory activities against HIV-2noD and HIV-2cBL_20-induced cytopathic effects with ECs0 values of 18.88 and 31.90 ng.mL 1. The inhibitory activities of wikstroelide M on the three HIV-1 strains were further confirmed by p24 quantification assay, with ECs0 values ranging from 15.16 to 35.57 ng.mL-1. Wikstroelide M also potently inhibited HIV-lnm induced cytolysis in MT-4 cells, with an ECs0 value of 9.60 ng.mL ~. The mechanistic assay showed that wikstroelide M targeted HIV-I reverse transcriptase and nuclear translocation of integrase through disrupting the interaction between integrase and LEDGF/p75. CONCLUSION： Wikslroelide M may be a potent HIV-1 and HIV-2 inhibitor, the mechanisms of action may include inhibition of reverse trascriptase activity and inhibition of integrase nuclear Iranslocation through dismpting the interaction between integrase and LEDGF/p75.展开更多
In this paper,the reverse forms of the L p-Busemann-Petty centroid inequality are shown. As the applications of the reverse forms,we obtain the reverse forms of the L p-centroid-affine inequality and an upper bound of...In this paper,the reverse forms of the L p-Busemann-Petty centroid inequality are shown. As the applications of the reverse forms,we obtain the reverse forms of the L p-centroid-affine inequality and an upper bound of the isotropic constant for convex bodies.展开更多
α-Hederagenin(H),derived from Hedera nepalensis var.sinensis,is a pentacyclic oleane-type triterpenoid that exhibits clear cytotoxicity to different tumor cell lines.In this study,a series of novel C-28 derivatives o...α-Hederagenin(H),derived from Hedera nepalensis var.sinensis,is a pentacyclic oleane-type triterpenoid that exhibits clear cytotoxicity to different tumor cell lines.In this study,a series of novel C-28 derivatives of hederagenin(H) were designed and synthesized in attempt to develop potent tumor resistance reverse activities agents.Previous research showed that H6 displayed robust reverse activity for paclitaxel resistance in KBV cells.Importantly,Co-treatment of paclitaxel with H6 significantly reduced the tumor weight to 42%.Pleasingly,H6 enhanced the efficacy of paclitaxel against KBV cancer cell-derived xenograft tumors in nude mice.Mechanism studies had found that H6 activated permeability glycoprotein(P-gp) ATPase,reduced intracellular ATP levels and inhibited efflux of P-gp substrates,thus enhancing the antitumor activity of paclitaxel on KBV cells.Molecular docking analysis of homology P-gp and H6 then conducted using the Surflex-Dock module.H6 showed a high binding affinity docking score with a total score of 5.4148,much higher than that of H(0.1414).The nov.el C-28 derivatives of H was synthesized from H6 via three-step reaction.The reversal activity of all synthesized H derivatives were tested using the MTT assay.The results showed that the derivatives of nitrogen groups at C-28 displayed same even potent activity than parent compound H6.In addition,its underlying mechanism of action and in vivo activity are in explore.展开更多
Background:P16 inactivation is frequently accompanied by telomerase reverse transcriptase(TERT)amplification in human cancer genomes.P16 inactivation by DNA methylation often occurs automatically during immortalizatio...Background:P16 inactivation is frequently accompanied by telomerase reverse transcriptase(TERT)amplification in human cancer genomes.P16 inactivation by DNA methylation often occurs automatically during immortalization of normal cells by TERT.However,direct evidence remains to be obtained to support the causal effect of epigenetic changes,such as P16 methylation,on cancer development.This study aimed to provide experimental evidence that P16 methylation directly drives cancer development.Methods:A zinc finger protein-based P16-specific DNA methyltransferase(P16-Dnmt)vector containing a“Tet-On”switch was used to induce extensive methylation of P16 CpG islands in normal human fibroblast CCD-18Co cells.Battery assays were used to evaluate cell immortalization and transformation throughout their lifespan.Cell subcloning and DNA barcoding were used to track the diversity of cell evolution.Results:Leaking P16-Dnmt expression(without doxycycline-induction)could specifically inactivate P16 expression by DNA methylation.P16 methylation only promoted proliferation and prolonged lifespan but did not induce immortalization of CCD-18Co cells.Notably,cell immortalization,loss of contact inhibition,and anchorage-independent growth were always prevalent in P16-Dnmt&TERT cells,indicating cell transformation.In contrast,almost all TERT cells died in the replicative crisis.Only a few TERT cells recovered from the crisis,in which spontaneous P16 inactivation by DNA methylation occurred.Furthermore,the subclone formation capacity of P16-Dnmt&TERT cells was two-fold that of TERT cells.DNA barcoding analysis showed that the diversity of the P16-Dnmt&TERT cell population was much greater than that of the TERT cell population.Conclusion:P16 methylation drives TERT-mediated immortalization and transformation of normal human cells that may contribute to cancer development.展开更多
The ability of two dihydrostilbene derivatives erianin and chrysotoxine from Dendrobium chrysotoxum to reverse multidrug resistant (MDR) cells was investigated using murine B16 melanoma cells transfected with the huma...The ability of two dihydrostilbene derivatives erianin and chrysotoxine from Dendrobium chrysotoxum to reverse multidrug resistant (MDR) cells was investigated using murine B16 melanoma cells transfected with the human MDR 1 gene and crossresistant to vinblastine and adriamycin (B16/h MDR 1 cells). Both of the two compounds were shown to increase the accumulation of adriamycin, the P glycoprotein (P gp) substrate, in B16/h MDR 1 transfectants.展开更多
P-glycoprotein (P-gp), a member of the ATP-binding cassette (ABC) family of transporters, plays a crucial role in the development of multi-drug resistance (MDR) in cancer treatment. P-gp actively pumps chemotherapeuti...P-glycoprotein (P-gp), a member of the ATP-binding cassette (ABC) family of transporters, plays a crucial role in the development of multi-drug resistance (MDR) in cancer treatment. P-gp actively pumps chemotherapeutic drugs out of cancer cells, reducing their intracellular concentrations and thereby diminishing their efficacy. This review explores the mechanisms by which P-gp contributes to MDR, including intrinsic and acquired resistance. It also discusses various strategies to inhibit P-gp, such as blocking drug binding sites, interfering with ATP hydrolysis, and altering cell membrane integrity. The potential of fourth-generation P-gp inhibitors and other novel approaches to enhance the effectiveness of cancer therapies is also examined. Understanding and overcoming P-gp-mediated MDR is essential for improving therapeutic outcomes in cancer patients.展开更多
基金supported by the Scientific Foundation and Teacher’s Foundation of Guangdong Pharmaceutical University (No.2006GGW01)the National Natural Science Foundation of China (No.30271110)
文摘Objective To investigate the effects of sodium selenite on telomerase activity, apoptosis and expression of TERT, c-myc and p53 in rat hepatocytes. Methods Selenium at doses of 2.5, 5.0, and 10 μmol/kg was given to SD rats by garage. In rat hepatocytes, telomerase activity was measured by the telomeric repeat amplification protocol （TRAP）, apoptosis was detected by flow cytometry, and expressions of telomerase reverse transcriptase （TERT）, c-myc and p53 were analyzed by reverse transcription-polymerase chain reaction （RT-PCR）. c-Myc and P53 proteins were detected by immunochemistry. Results Selenium at doses of 2.5, 5.0, and 10 μmol/kg significantly increased hepatocellular telomerase activity and induced apoptosis in a dose-dependent manner. Although selenium at doses of 2.5, 5.0, and 10 μmol/kg displayed no obvious enhancing effect on the TERT mRNA expression in rat hepatocytes （P〉0.05）, it significantly increased the c-myc mRNA and p53 mRNA expression at the dose of 10 μmol/kg （P〈0.05）. Selenium at doses of 5.0 and 10 μmol/kg obviously increased the content of P53 protein in rat hepatocytes, but only at the dose of 10 μmol/kg, it significantly promoted the value of c-Myc protein in them. Conclusion Selenium can slightly increase telomerase activity and TERT expression, and significantly induce apoptosis and over-expression of c-myc and p53 at relatively high doses. The beneficial effects of selenium on senescence and aging may be mediated by telomerase activation and expression of TERT, c-myc, and p53 in rat hepatocytes.
基金funded by the Key Research and Development Program of Anhui Province,China(201904a06020016 and 202104g01020013)the National Natural Science Foundation of China(31101204)the Program of Rice Genetic Breeding Key Laboratory of Anhui Province,China(SDKF-201903)。
文摘The discovery and application of environment-sensitive genic male sterile(EGMS) rice germplasm provide an easy method for hybrid rice breeding and have made great contributions to hybrid rice production. Typically, the photoperiod-and thermosensitive GMS(P/TGMS) lines utilized in two-line hybrid systems are male sterile under long day or/and high temperature but fertile under short day or/and low temperature conditions. However, Yannong S(Yn S), a reverse TGMS(rTGMS) line, is sterile under low temperature(<29℃) and fertile under high temperature(>29.5℃). Here, we report a genetic study on the rTGMS trait in Yn S. Interestingly, the F1 plants of the cross between Yn S and a cultivar, L422, were male sterile at 22℃ and completely fertile at 27℃. Moreover, the segregation ratio of fertile and sterile individuals in Yn S/L422 F2 populations changed from 1:3.05 to 2.95:1 when the ambient temperature increased, showing that the rTGMS trait exhibits semidominance in Yn S. We further found a locus on chromosome 10, termed RTMS10, which controls the rTGMS trait in Yn S. We then finely mapped RTMS10 to a ~68 kb interval between markers ID13116 and ID1318 by Yn S/L422 BC6 F2 populations. A near iso-genic line(NIL) NL1 from the BC6 F3 generation was developed and the pollen of NL1 became abnormal from the meiosis stage under low temperature. In summary, we identified an rTGMS locus, RTMS10, and provided co-segregated markers, which could help to accelerate molecular breeding of rTGMS lines and better understand the rTGMS trait in rice.
基金the National Key Basic Research Program of China,No. 2006cb500700the National Natural Science Foundation of China,No.30470904the Natural Science and Technology Foundation of Guangdong Province,No. 04009356, 2008B030301320
文摘BACKGROUND： Numerous current studies have suggested that human telomerase reverse transcriptase （hTERT） gene has neuroprotective effects and can inhibit apoptosis induced by various cytotoxic stresses; however, the mechanism of action remains unknown. OBJECTIVE： To evaluate the neuroprotective effects and possible mechanism of action of hTERT gene transfection in human embryonic cortical neurons treated with beta-amyloid fragment 25-35 （AI325-35）. DESIGN, TIME AND SETTING： The randomized, controlled and molecular biological studies were performed at the Department of Anatomy and Brain Research, Zhongshan School of Medicine, Sun Yat-sen University, China, from September 2005 to June 2008. MATERIALS： AdEasy-1 Expression System was gifted by Professor Guoquan Gao from Sun Yat-Sen University, China. Human cortical neurons were derived from 12-20 week old aborted fetuses, obtained from the Guangzhou Maternal and Child Health Hospital, China. Mouse anti-Odk5 and mouse anti-p16 monoclonal antibodies （Lab Vision, USA）, and mouse anti-hTERT monoclonal antibody （Epitomics, USA）, were used in this study. METHODS： （1） Recombinant adenovirus vectors, encoding hTERT （Ad-hTERT） and green fluorescent protein （Ad-GFP）, were constructed using the AdEasy-1 Expression System. Human embryonic cortical neurons in the Ad-hTERT group were transfected with Ad-hTERT for 1-21 days. Likewise, human embryonic cortical neurons in the Ad-GFP group were transfected with Ad-GFP for 1-21 days. Human embryonic cortical neurons in the control group were cultured as normal. （2） Human embryonic cortical neurons in the Ad-hTERT group were treated with 10 pmol/L Aβ25-35 for 24 hours. Normal human embryonic cortical neurons treated with 10 pmol/Lβ25.35 for 24 hours served as a model group. Human embryonic cortical neurons in the Ad-GFP and control groups were not treated with Aβ25-35. MAIN OUTCOME MEASURES： Expression of hTERT in human embryonic cortical neurons was evaluated by immunocytochemical staining and Western blot assay. Telomerase activity was measured using a PCR-based telomeric repeat amplification protocol （TRAP） ELISA kit. Neural activity in human embryonic cortical neurons was examined by MTT assay; apoptosis was measured using TUNEL assay; and Cdk5 and p16 protein expressions were measured by Western blot. RESULTS： Expression of hTERT protein was significantly increased and peaked at day 3 post-transfection in the Ad-hTERT group. No hTERT expression was detected in the Ad-GFP and control groups. Telomerase activity was significantly greater in the Ad-hTERT group compared with the Ad-GFP and control groups （P 〈 0.01）. Compared with the control group, cell activity was significantly decreased （P 〈 0.05）, and cell apoptotic rate, Cdk5 and p16 expression were significantly increased （P 〈 0.01） in the model group. Compared with the model group, cell activity was increased in the Ad-hTERT group, and peaked at day 3 post-transfection （P 〈 0.05）. Neuroprotective effects also peaked at day 3 post-transfection; and the apoptotic rate, Cdk5 and p16 expression significantly decreased （P 〈 0.01）. CONCLUSION： Expression of hTERT in human embryonic cortical neurons can relieve Aβ25-35-induced neuronal apoptosis. The possible mechanism by which hTERT produces these neuroprotective effects may be associated with inhibition of Cdk5 and p16 expression.
基金supported,in part,by grants from the National Natural Science Foundation of China(Nos.81102483,81001462)the 973 Program(No.2009CB522306)the Key Scientific and Technological Program of China(Nos.2009-ZX09501-029,2012ZX10001-006,2012ZX10001-007,2012ZX-09103-101-022),and Yunnan(No.2010GA001)
文摘AIM： To evaluate the anti-HIV activity and mechanism of action of wikstroelide M, a daphnane diterpene from Daphne acutiloba Rehder （Thymelaeaceae）. METHOD： The anti-HIV activities of wikstroelide M against different HIV strains were evaluated by cytopathic effect assay and p24 quantification assay with ELISA. The inhibitory effect of wikstroelide M on HIV reverse transcription was analyzed by real-time PCR and ELISA. The effect of wikstroelide M on HIV-1 integrase nuclear translocation was observed with a cell-based imaging assay. The effect of wikstroelide M on LEDGF/p75-IN interaction was assayed by molecular docking. RESULTS： Wikstroelide M potently inhibited different HIV-1 strains, including HIV-lmn, HIV-1AI7, and HIV-19495, induced a cytopathic effect, with ECs0 values ranging from 3.81 to 15.65 ng.mL-I. Wikstroelide M also had high inhibitory activities against HIV-2noD and HIV-2cBL_20-induced cytopathic effects with ECs0 values of 18.88 and 31.90 ng.mL 1. The inhibitory activities of wikstroelide M on the three HIV-1 strains were further confirmed by p24 quantification assay, with ECs0 values ranging from 15.16 to 35.57 ng.mL-1. Wikstroelide M also potently inhibited HIV-lnm induced cytolysis in MT-4 cells, with an ECs0 value of 9.60 ng.mL ~. The mechanistic assay showed that wikstroelide M targeted HIV-I reverse transcriptase and nuclear translocation of integrase through disrupting the interaction between integrase and LEDGF/p75. CONCLUSION： Wikslroelide M may be a potent HIV-1 and HIV-2 inhibitor, the mechanisms of action may include inhibition of reverse trascriptase activity and inhibition of integrase nuclear Iranslocation through dismpting the interaction between integrase and LEDGF/p75.
基金Supported by the National Natural Science Foundation of China (10671117)Academic Mainstay Foundation of Hubei Provincial De-partment of Education (D200729002)Science Foundation of China Three Gorges University
文摘In this paper,the reverse forms of the L p-Busemann-Petty centroid inequality are shown. As the applications of the reverse forms,we obtain the reverse forms of the L p-centroid-affine inequality and an upper bound of the isotropic constant for convex bodies.
基金supported by State Key Laboratory of Drug Research(SIMM1705KF-07)
文摘α-Hederagenin(H),derived from Hedera nepalensis var.sinensis,is a pentacyclic oleane-type triterpenoid that exhibits clear cytotoxicity to different tumor cell lines.In this study,a series of novel C-28 derivatives of hederagenin(H) were designed and synthesized in attempt to develop potent tumor resistance reverse activities agents.Previous research showed that H6 displayed robust reverse activity for paclitaxel resistance in KBV cells.Importantly,Co-treatment of paclitaxel with H6 significantly reduced the tumor weight to 42%.Pleasingly,H6 enhanced the efficacy of paclitaxel against KBV cancer cell-derived xenograft tumors in nude mice.Mechanism studies had found that H6 activated permeability glycoprotein(P-gp) ATPase,reduced intracellular ATP levels and inhibited efflux of P-gp substrates,thus enhancing the antitumor activity of paclitaxel on KBV cells.Molecular docking analysis of homology P-gp and H6 then conducted using the Surflex-Dock module.H6 showed a high binding affinity docking score with a total score of 5.4148,much higher than that of H(0.1414).The nov.el C-28 derivatives of H was synthesized from H6 via three-step reaction.The reversal activity of all synthesized H derivatives were tested using the MTT assay.The results showed that the derivatives of nitrogen groups at C-28 displayed same even potent activity than parent compound H6.In addition,its underlying mechanism of action and in vivo activity are in explore.
基金National Natural Science Foundation of China(Nos.81773036,82073102,82073107,and 31261140372)Beijing Municipal Natural Science Foundation(No.7222022)
文摘Background:P16 inactivation is frequently accompanied by telomerase reverse transcriptase(TERT)amplification in human cancer genomes.P16 inactivation by DNA methylation often occurs automatically during immortalization of normal cells by TERT.However,direct evidence remains to be obtained to support the causal effect of epigenetic changes,such as P16 methylation,on cancer development.This study aimed to provide experimental evidence that P16 methylation directly drives cancer development.Methods:A zinc finger protein-based P16-specific DNA methyltransferase(P16-Dnmt)vector containing a“Tet-On”switch was used to induce extensive methylation of P16 CpG islands in normal human fibroblast CCD-18Co cells.Battery assays were used to evaluate cell immortalization and transformation throughout their lifespan.Cell subcloning and DNA barcoding were used to track the diversity of cell evolution.Results:Leaking P16-Dnmt expression(without doxycycline-induction)could specifically inactivate P16 expression by DNA methylation.P16 methylation only promoted proliferation and prolonged lifespan but did not induce immortalization of CCD-18Co cells.Notably,cell immortalization,loss of contact inhibition,and anchorage-independent growth were always prevalent in P16-Dnmt&TERT cells,indicating cell transformation.In contrast,almost all TERT cells died in the replicative crisis.Only a few TERT cells recovered from the crisis,in which spontaneous P16 inactivation by DNA methylation occurred.Furthermore,the subclone formation capacity of P16-Dnmt&TERT cells was two-fold that of TERT cells.DNA barcoding analysis showed that the diversity of the P16-Dnmt&TERT cell population was much greater than that of the TERT cell population.Conclusion:P16 methylation drives TERT-mediated immortalization and transformation of normal human cells that may contribute to cancer development.
文摘The ability of two dihydrostilbene derivatives erianin and chrysotoxine from Dendrobium chrysotoxum to reverse multidrug resistant (MDR) cells was investigated using murine B16 melanoma cells transfected with the human MDR 1 gene and crossresistant to vinblastine and adriamycin (B16/h MDR 1 cells). Both of the two compounds were shown to increase the accumulation of adriamycin, the P glycoprotein (P gp) substrate, in B16/h MDR 1 transfectants.
文摘P-glycoprotein (P-gp), a member of the ATP-binding cassette (ABC) family of transporters, plays a crucial role in the development of multi-drug resistance (MDR) in cancer treatment. P-gp actively pumps chemotherapeutic drugs out of cancer cells, reducing their intracellular concentrations and thereby diminishing their efficacy. This review explores the mechanisms by which P-gp contributes to MDR, including intrinsic and acquired resistance. It also discusses various strategies to inhibit P-gp, such as blocking drug binding sites, interfering with ATP hydrolysis, and altering cell membrane integrity. The potential of fourth-generation P-gp inhibitors and other novel approaches to enhance the effectiveness of cancer therapies is also examined. Understanding and overcoming P-gp-mediated MDR is essential for improving therapeutic outcomes in cancer patients.
