AIM:To study the inhibition of tumor angiogenesis by 5,2,4'-trihydroxy-6,7,5'-trimethoxyflavone(TTF1) isolated from an extract of herbal medicine Sorbaria sorbifolia.METHODS:Angiogenic activity was assayed usi...AIM:To study the inhibition of tumor angiogenesis by 5,2,4'-trihydroxy-6,7,5'-trimethoxyflavone(TTF1) isolated from an extract of herbal medicine Sorbaria sorbifolia.METHODS:Angiogenic activity was assayed using the chick embryo chorioallantoic membrane(CAM) method.Microvessel density(MVD) was determined by staining tissue sections immunohistochemically for CD34 using the Weidner capillary counting method.The mRNA and protein levels of vascular endothelial growth factor(VEGF),vascular endothelialgrowth factor receptor 2(VEGFR2,Flk-1/KDR),basic fibroblast growth factor(bFGF),cyclo-oxygenase(COX)-2 and hypoxia-inducible factor(HIF)-1α were detected by quantitative real-time polymerase chain reaction and Western blotting analysis.RESULTS:The TTF1 inhibition rates for CAM were 30.8%,38.2% and 47.5% with treatment concentrations of 25,50 and 100 μg/embryo × 5 d,respectively.The inhibitory rates for tumor size were 43.8%,49.4% and 59.6% at TTF1 treatment concentrations of 5,10,and 20 μmol/kg,respectively.The average MVD was 14.2,11.2 and 8.5 at treatment concentrations of 5 μmol/kg,10 μmol/kg and 20 μmol/kg TTF1,respectively.The mRNA and protein levels of VEGF,KDR,bFGF,COX-2 and HIF-1α in mice treated with TTF1 were significantly decreased.CONCLUSION:TTF1 can inhibit tumor angiogenesis,and the mechanism may be associated with the down-regulation of VEGF,KDR,bFGF,HIF-1α and COX-2.展开更多
18S,5.8S,and 28S ribosomal RNAs(rRNAs)are cotranscribed as a pre-ribosomal RNA(pre-rRNA)from the rDNA by RNA polymerase I whose activity is vigorous during the S-phase,leading to a conflict with rDNA replication.This ...18S,5.8S,and 28S ribosomal RNAs(rRNAs)are cotranscribed as a pre-ribosomal RNA(pre-rRNA)from the rDNA by RNA polymerase I whose activity is vigorous during the S-phase,leading to a conflict with rDNA replication.This conflict is resolved partly by replication-fork-barrier(RFB)-sites sequences located downstream of the rDNA and RFB-binding proteins such as Ttf1.However,how Ttf1 is displaced from RFB-sites to allow replication fork progression remains elusive.Here,we reported that loss-of-function of Bms1l,a nucleolar GTPase,upregulates rDNA transcription,causes replication-fork stall,and arrests cell cycle at the S-to-G2 transition;however,the G1-to-S transition is constitutively active characterized by persisting DNA synthesis.Concomitantly,ubf,tif-IA,and taf1b marking rDNA transcription,Chk2,Rad51,and p53 marking DNA-damage response,and Rpa2,PCNA,Fen1,and Ttf1 marking replication fork stall are all highly elevated in bms1l mutants.We found that Bms1 interacts with Ttf1 in addition to Rc1l.Finally,we identified RFB-sites for zebrafish Ttf1 through chromatin immunoprecipitation sequencing and showed that Bms1 disassociates the Ttf1–RFB complex with its GTPase activity.We propose that Bms1 functions to balance rDNA transcription and replication at the S-phase through interaction with Rcl1 and Ttf1,respectively.TTF1 and Bms1 together might impose an S-phase checkpoint at the rDNA loci.展开更多
基金Supported by The National Natural Science Foundation Grant,No. 30860374
文摘AIM:To study the inhibition of tumor angiogenesis by 5,2,4'-trihydroxy-6,7,5'-trimethoxyflavone(TTF1) isolated from an extract of herbal medicine Sorbaria sorbifolia.METHODS:Angiogenic activity was assayed using the chick embryo chorioallantoic membrane(CAM) method.Microvessel density(MVD) was determined by staining tissue sections immunohistochemically for CD34 using the Weidner capillary counting method.The mRNA and protein levels of vascular endothelial growth factor(VEGF),vascular endothelialgrowth factor receptor 2(VEGFR2,Flk-1/KDR),basic fibroblast growth factor(bFGF),cyclo-oxygenase(COX)-2 and hypoxia-inducible factor(HIF)-1α were detected by quantitative real-time polymerase chain reaction and Western blotting analysis.RESULTS:The TTF1 inhibition rates for CAM were 30.8%,38.2% and 47.5% with treatment concentrations of 25,50 and 100 μg/embryo × 5 d,respectively.The inhibitory rates for tumor size were 43.8%,49.4% and 59.6% at TTF1 treatment concentrations of 5,10,and 20 μmol/kg,respectively.The average MVD was 14.2,11.2 and 8.5 at treatment concentrations of 5 μmol/kg,10 μmol/kg and 20 μmol/kg TTF1,respectively.The mRNA and protein levels of VEGF,KDR,bFGF,COX-2 and HIF-1α in mice treated with TTF1 were significantly decreased.CONCLUSION:TTF1 can inhibit tumor angiogenesis,and the mechanism may be associated with the down-regulation of VEGF,KDR,bFGF,HIF-1α and COX-2.
基金by the National Key R&D Program of China(2018YFA0800501)the National Natural Science Foundation of China(31771596 and 32000565).
文摘18S,5.8S,and 28S ribosomal RNAs(rRNAs)are cotranscribed as a pre-ribosomal RNA(pre-rRNA)from the rDNA by RNA polymerase I whose activity is vigorous during the S-phase,leading to a conflict with rDNA replication.This conflict is resolved partly by replication-fork-barrier(RFB)-sites sequences located downstream of the rDNA and RFB-binding proteins such as Ttf1.However,how Ttf1 is displaced from RFB-sites to allow replication fork progression remains elusive.Here,we reported that loss-of-function of Bms1l,a nucleolar GTPase,upregulates rDNA transcription,causes replication-fork stall,and arrests cell cycle at the S-to-G2 transition;however,the G1-to-S transition is constitutively active characterized by persisting DNA synthesis.Concomitantly,ubf,tif-IA,and taf1b marking rDNA transcription,Chk2,Rad51,and p53 marking DNA-damage response,and Rpa2,PCNA,Fen1,and Ttf1 marking replication fork stall are all highly elevated in bms1l mutants.We found that Bms1 interacts with Ttf1 in addition to Rc1l.Finally,we identified RFB-sites for zebrafish Ttf1 through chromatin immunoprecipitation sequencing and showed that Bms1 disassociates the Ttf1–RFB complex with its GTPase activity.We propose that Bms1 functions to balance rDNA transcription and replication at the S-phase through interaction with Rcl1 and Ttf1,respectively.TTF1 and Bms1 together might impose an S-phase checkpoint at the rDNA loci.
