In this study, we isolated a polysaccharide from Branchiostoma belcheri （PBB） by enzymatic protein hydrolysis and alcohol precipitation. We investigated the effects of PBB supplementation on DNA oxidation and growth...In this study, we isolated a polysaccharide from Branchiostoma belcheri （PBB） by enzymatic protein hydrolysis and alcohol precipitation. We investigated the effects of PBB supplementation on DNA oxidation and growth of the transplanted tumor cells Sarcoma （S180） in mice. Sixty healthy Kunming mice weighing between 18 and 25 g were randomly assigned to 6 groups, each consisting of 10 animals. All the mice, except for the blank control group, were inoculated with S180 sarcoma cells into the axilla of the left foreleg. PBB was given to mice by gavage at doses of 0 （model control）, 25, 50, or 100 mg/kg b.w. in 0.2 ml saline for 30 days. The fifth group of S180-mice was given cytoxan （50 mg/kg） by peritoneal injection as a positive control group. The animals had free access to food and water. The mice were sacrificed after the final treatment and blood was quickly collected. Spontaneous and oxidized DNA damage of peripheral lymphocytes induced by H2O2 were analyzed by SCGE. O6-methyl-guanine （O6-MeG） was measured by high-performance capillary zone electrophoresis. The average tumor weights （0.856-1.118 g） of the three PBB groups were significantly lower than that of the model control group （1.836 g） （p〈0.05）. The tumor inhibition ratios of the PBB groups were 39.1%-53.4% and similar to the cytoxan positive group （57.5%）. There were no significant differences in spontaneous DNA damage in peripheral lymphocytes among the groups. The oxidative DNA damage induced by 10 μmol/L H2O2 in the 50 and 100 mg/kg b.w. groups were 246.1 AU and 221.7 AU, respectively, both of which were significantly lower than that in the model group （289.0 AU; p〈0.05）. The plasma concentrations of O6-MeG in the 25, 50, and 100 mg/kg supplemented groups were 2.09 μmol/L, 1.86 μmol/L, and 1.63 lamol/L, respectively, all of which were significantly lower than that of the model group （2.67 μmol/L; p〈0.05）. These results indicated that PBB may have antioxidative activity and thus reduce oxidation-induced DNA damage.展开更多
O6-methylguanine DNA methyltransferase(MGMT), a DNA repair enzyme, has been reported in some congenital malformations, but it is less frequently reported in neural tube defects. This study investigated MGMT mRNA expre...O6-methylguanine DNA methyltransferase(MGMT), a DNA repair enzyme, has been reported in some congenital malformations, but it is less frequently reported in neural tube defects. This study investigated MGMT mRNA expression and methylation levels in the early embryo and in different embryonic stages, as well as the relationship between MGMT and neural tube defects. Spina bifida aperta was induced in rats by a single intragastric administration of all-trans retinoic acid on embryonic day(E) 10, whereas normal control rats received the same amount of olive oil on the same embryonic day. DNA damage was assessed by detecting γ-H2 A.X in spina bifida aperta rats. Real time-polymerase chain reaction was used to examine mRNA expression of MGMT in normal control and spina bifida aperta rats. In normal controls, the MGMT mRNA expression decreased with increasing embryonic days, and was remarkably reduced from E11 to E14, reaching a minimum at E18. In the spina bifida aperta model, γ-H2 A.X protein expression was increased, and mRNA expression of MGMT was markedly decreased on E14, E16, and E18. Bisulfite sequencing polymerase chain reaction for MGMT promoter methylation demonstrated that almost all CpG sites in the MGMT promoter remained unmethylated in both spina bifida aperta rats and normal controls, and there was no significant difference in methylation level between the two groups on either E14 or E18. Our results show that DNA damage occurs in spina bifida aperta rats. The mRNA expression of MGMT is downregulated, and this downregulation is independent of promoter DNA methylation.展开更多
O6-methylguanine DNA methyltransferase(MGMT) gene promoter methylation plays an important role in colorectal carcinogenesis, occurring in about 30%-40% of metastatic colorectal cancer. Its prognostic role has not been...O6-methylguanine DNA methyltransferase(MGMT) gene promoter methylation plays an important role in colorectal carcinogenesis, occurring in about 30%-40% of metastatic colorectal cancer. Its prognostic role has not been defined yet, but loss of expression of MGMT, which is secondary to gene promoter methylation, results in an interesting high response to alkylating agents such as dacarbazine and temozolomide. In a phase 2 study on heavily pre-treated patients with MGMT methylated metastatic colorectal cancer, temozolomide achieved about 30% of disease control rate. Activating mutations of RAS or BRAF genes as well as mismatch repair deficiency may represent mechanisms of resistance to alkylating agents, but a dose-dense schedule of temozolomide may potentially restore sensitivity in RAS-mutant patients. Further development of temozolomide in MGMT methylated colorectal cancer includes investigation of synergic combinations with other agents such as fluoropyrimidines and research for additional biomarkers, in order to better define the role of temozolomide in the treatment of individual patients.展开更多
文摘In this study, we isolated a polysaccharide from Branchiostoma belcheri （PBB） by enzymatic protein hydrolysis and alcohol precipitation. We investigated the effects of PBB supplementation on DNA oxidation and growth of the transplanted tumor cells Sarcoma （S180） in mice. Sixty healthy Kunming mice weighing between 18 and 25 g were randomly assigned to 6 groups, each consisting of 10 animals. All the mice, except for the blank control group, were inoculated with S180 sarcoma cells into the axilla of the left foreleg. PBB was given to mice by gavage at doses of 0 （model control）, 25, 50, or 100 mg/kg b.w. in 0.2 ml saline for 30 days. The fifth group of S180-mice was given cytoxan （50 mg/kg） by peritoneal injection as a positive control group. The animals had free access to food and water. The mice were sacrificed after the final treatment and blood was quickly collected. Spontaneous and oxidized DNA damage of peripheral lymphocytes induced by H2O2 were analyzed by SCGE. O6-methyl-guanine （O6-MeG） was measured by high-performance capillary zone electrophoresis. The average tumor weights （0.856-1.118 g） of the three PBB groups were significantly lower than that of the model control group （1.836 g） （p〈0.05）. The tumor inhibition ratios of the PBB groups were 39.1%-53.4% and similar to the cytoxan positive group （57.5%）. There were no significant differences in spontaneous DNA damage in peripheral lymphocytes among the groups. The oxidative DNA damage induced by 10 μmol/L H2O2 in the 50 and 100 mg/kg b.w. groups were 246.1 AU and 221.7 AU, respectively, both of which were significantly lower than that in the model group （289.0 AU; p〈0.05）. The plasma concentrations of O6-MeG in the 25, 50, and 100 mg/kg supplemented groups were 2.09 μmol/L, 1.86 μmol/L, and 1.63 lamol/L, respectively, all of which were significantly lower than that of the model group （2.67 μmol/L; p〈0.05）. These results indicated that PBB may have antioxidative activity and thus reduce oxidation-induced DNA damage.
基金supported by the National Natural Science Foundation of China,No.81671469,81171072(to ZWY)the National Basic Research Program of China(973 Program),No.2013CB945402(to ZWY)the Program for Liaoning Innovative Research Team in University of China,No.LT2013016(to ZWY)
文摘O6-methylguanine DNA methyltransferase(MGMT), a DNA repair enzyme, has been reported in some congenital malformations, but it is less frequently reported in neural tube defects. This study investigated MGMT mRNA expression and methylation levels in the early embryo and in different embryonic stages, as well as the relationship between MGMT and neural tube defects. Spina bifida aperta was induced in rats by a single intragastric administration of all-trans retinoic acid on embryonic day(E) 10, whereas normal control rats received the same amount of olive oil on the same embryonic day. DNA damage was assessed by detecting γ-H2 A.X in spina bifida aperta rats. Real time-polymerase chain reaction was used to examine mRNA expression of MGMT in normal control and spina bifida aperta rats. In normal controls, the MGMT mRNA expression decreased with increasing embryonic days, and was remarkably reduced from E11 to E14, reaching a minimum at E18. In the spina bifida aperta model, γ-H2 A.X protein expression was increased, and mRNA expression of MGMT was markedly decreased on E14, E16, and E18. Bisulfite sequencing polymerase chain reaction for MGMT promoter methylation demonstrated that almost all CpG sites in the MGMT promoter remained unmethylated in both spina bifida aperta rats and normal controls, and there was no significant difference in methylation level between the two groups on either E14 or E18. Our results show that DNA damage occurs in spina bifida aperta rats. The mRNA expression of MGMT is downregulated, and this downregulation is independent of promoter DNA methylation.
文摘O6-methylguanine DNA methyltransferase(MGMT) gene promoter methylation plays an important role in colorectal carcinogenesis, occurring in about 30%-40% of metastatic colorectal cancer. Its prognostic role has not been defined yet, but loss of expression of MGMT, which is secondary to gene promoter methylation, results in an interesting high response to alkylating agents such as dacarbazine and temozolomide. In a phase 2 study on heavily pre-treated patients with MGMT methylated metastatic colorectal cancer, temozolomide achieved about 30% of disease control rate. Activating mutations of RAS or BRAF genes as well as mismatch repair deficiency may represent mechanisms of resistance to alkylating agents, but a dose-dense schedule of temozolomide may potentially restore sensitivity in RAS-mutant patients. Further development of temozolomide in MGMT methylated colorectal cancer includes investigation of synergic combinations with other agents such as fluoropyrimidines and research for additional biomarkers, in order to better define the role of temozolomide in the treatment of individual patients.
