DNA修复基因MGMT启动子区过甲基化与脑胶质瘤
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摘要
目的:目前的研究已经证实DNA修复酶—O~6-甲基鸟嘌呤-DNA甲基转移酶(O~6-methylguanine DNA methyltransferase,MGMT)在脑胶质瘤组织中表达与肿瘤细胞对BCNU等亚硝脲类药物的耐药密切相关,并影响肿瘤的化疗效果和病人的预后。在许多肿瘤中发现启动子区过甲基化而导致MGMT基因的转录失活,但是启动予区过甲基化与MGMT蛋白的表达、化疗耐药及患者预后之间的关系尚未完全阐明。本文拟从三个方面对MGMT基因启动子甲基化进行研究:1)人脑胶质瘤细胞株MGMT基因启动子过甲基化同细胞株对BCNU耐药的关系;2)胶质瘤患者肿瘤组织MGMT基因启动子过甲基化和肿瘤组织中MGMT蛋白表达的关系;3)胶质瘤患者肿瘤组织和其对应血清中MGMT基因启动子过甲基化是否有一致性。
材料与方法:研究对象为9株人脑胶质瘤细胞株、27例临床胶质瘤患者的肿瘤组织和其对应的血清。采用美国Gentra公司的试剂盒以盐析法提取基因组DNA,并采用美国Chemicon公司CpGenome~(TM) DNA修饰试剂盒对组织DNA进行亚硫酸氢盐修饰,采用甲基化特异性PCR法(Methylation-specific PCR,MSP)进行MGMT基因启动子区甲基化水平的检测;采用sulforhodamine B(SRB)Colorimetric抗癌药筛选法测定人脑胶质瘤细胞株对BCNU的敏感性;采用免疫组化的方法来检测胶质瘤患者肿瘤组织标本中MGMT蛋白表达程度。实验结果采用SPSS 12.0统计软件处
Objective: Previous studies show that the DNA-repair enzyme O~6-methylguanine-DNA-methyltransferase (MGMT) is one of drug resistant factors that affect chemosensibility of glioma. The MGMT gene has been shown to be silenced by promoter methylation in many human tumors. This study explored the relationship between the hypermethylation of CpG islands in the promoter regions of MGMT genes of cell lines and its sensitivity to BCNU; the relationship between the hypermethylation of CpG islands in the promoter regions of MGMT genes of glioma cells and the expression of MGMT and the concordance of the hypermethylation of CpG islands in the promoter regions of MGMT genes between tumor and paired serum of 27 glioma patients.Methods: In this research, 9 human glioma cell lines, 27 primary glioma tissues and paired serum were studied. Genomic DNA was extracted from tissues and paired serum using protocols provided by Gentra Puregene DNA purification kit. The DNA was modified by bisulfite reaction using the CpGenome DNA modification kit. Modified DNA was amplified by methylation-specic PCR (MSP) procedure to analyze the status of methylation. Methylation-specific PCR was used to study the promoter
methylation of the MGMT gene in glioma tissues and paired serum; the cell resistance to BCNU in human glioma cell lines was determined by SRB assay; MGMT expression was examined by immunohistochemistry method. The x~2 test, Fisher's Exact Test, Nonparametric statistics test and Spearman correlation coefficient were used for the statistics, P<0.05 was considered significant. Result:1. In the 6 cell lines which were hypermethylated, sensitivity to BCNU was noted in 5 cell lines; in the 3 cell lines which were unmethylated, resistance to BCNU was noted in all of the 3 cell lines. Spearman correlation coefficient was used to analysis the result. The relation was significant, P <0.05.2. The rate of MGMT gene promotor methylation of glioma tissues in maleand female were 55.6%(10/18) and 44.4%(4/9), respectively. However, the difference was not significant, P>0.05; The rate of MGMT gene promotor methylation of paired serum in male and female were 50.0% (9/18) and 44.4% (4/9), respectively. However, the difference was not significant, P >0.05.3. The rate of hypermethylation of the promoter of MGMT gene of glioma tissues was 36.3%(4/l 1) in patients aged not more than 50 years; the rate of hypermethylation of the promoter of MGMT gene was 62.5%(10/16) in patient aged more than 50 years. The differences in methylation rate among
the both groups were not significant, />>0.05; The rate of hypermethylation of the promoter of MGMT gene of paired serum was 36.3%(4/l 1) in patients aged not more than 50 years; the rate of hypermethy lation of the promoter of MGMT gene was 56.2%(9/16) in patient aged more than 50 years. The differences in methylation rate among the both groups were not significant, P>0.05.4. Of the 27 glioma tissues, the methylation rate of MGMT in Grade I > Grade II > Grade III and Grade IV groups were 0.0% (0/2X 50.0% (5/10), 57.1% (8/14) and 100%, respectively. There were no significant differences among these groups, P>0.05; Of the 27 paired serum, the methylation rate of MGMT in Grade I ^ Grade II ^ Grade III and Grade IV groups were 0.0%(0/2X 40.0% (4/1 OX 57.1% (8/14) and 100%, respectively. There were no significant differences among these groups, P>0.05.5. Among the 27 glioma samples, MGMT expression was noted in 18 samples, in which hypermethylation was detected in 7(38.9%) cases, while MGMT expression was not noted in 9 samples, in which hypermethylation was detected in 7(77.8%) cases. Spearman correlation coefficient was used to analysis the result. The relation was significant, P<0.05.6. MGMT status was studied in DNA extracted from 27 glioma samples and paired serum samples. Among the 27 gliomas samples, MGMT hypermethylation was detected in 14(51.9%) cases, while it was detected in 13(48.1%) paired serum samples; MGMT unmethylation was detected in
13(48.1%) gliomas samples, while it was detected in 14(51.9%) pairedserum samples. Spearman correlation coefficient was used to analysis theresult. The relation was significant, P<0.05.Conclusion:The present study demonstrates that the aberrant methylation of MGMTgene promoter may play an important role in the sensibility of glioma toalkylating agents.1. In human glioma cell lines, the relation between the aberrant methylation of CpG islands in the promoter regions of MGMT gene promoter and the cell resistant to BCNU is significant. If the MGMT gene promoter is hypermethylated, the cell lines are sensitive to BCNU, while if the MGMT gene promoter is unmethylated, the cell lines are resistant to BCNU,2. The relationship between the aberrant methylation of MGMT gene promoter and the expression of MGMT in glioma is significant, so is the relationship between the aberrant methylation of MGMT gene promoter and the sensibility of glioma to alkylating agents, While the aberrant methylation of promoter of MGMT gene does not show any significant relationship with clinical condition such as age, gender and pathological grading.3. The relation between the aberrant methylation of promoter of MGMT gene in glioma tissues and paired serum is significant. Methylated MGMT is found in serum DNA of glioma patients, with a good correlation between serum and primary tumor tissue. Methylation-specific PCR assay in serum
DNA could be a good predictive tool for selecting glioma patients to be treated with alkylating agents.
材料与方法:研究对象为9株人脑胶质瘤细胞株、27例临床胶质瘤患者的肿瘤组织和其对应的血清。采用美国Gentra公司的试剂盒以盐析法提取基因组DNA,并采用美国Chemicon公司CpGenome~(TM) DNA修饰试剂盒对组织DNA进行亚硫酸氢盐修饰,采用甲基化特异性PCR法(Methylation-specific PCR,MSP)进行MGMT基因启动子区甲基化水平的检测;采用sulforhodamine B(SRB)Colorimetric抗癌药筛选法测定人脑胶质瘤细胞株对BCNU的敏感性;采用免疫组化的方法来检测胶质瘤患者肿瘤组织标本中MGMT蛋白表达程度。实验结果采用SPSS 12.0统计软件处
Objective: Previous studies show that the DNA-repair enzyme O~6-methylguanine-DNA-methyltransferase (MGMT) is one of drug resistant factors that affect chemosensibility of glioma. The MGMT gene has been shown to be silenced by promoter methylation in many human tumors. This study explored the relationship between the hypermethylation of CpG islands in the promoter regions of MGMT genes of cell lines and its sensitivity to BCNU; the relationship between the hypermethylation of CpG islands in the promoter regions of MGMT genes of glioma cells and the expression of MGMT and the concordance of the hypermethylation of CpG islands in the promoter regions of MGMT genes between tumor and paired serum of 27 glioma patients.Methods: In this research, 9 human glioma cell lines, 27 primary glioma tissues and paired serum were studied. Genomic DNA was extracted from tissues and paired serum using protocols provided by Gentra Puregene DNA purification kit. The DNA was modified by bisulfite reaction using the CpGenome DNA modification kit. Modified DNA was amplified by methylation-specic PCR (MSP) procedure to analyze the status of methylation. Methylation-specific PCR was used to study the promoter
methylation of the MGMT gene in glioma tissues and paired serum; the cell resistance to BCNU in human glioma cell lines was determined by SRB assay; MGMT expression was examined by immunohistochemistry method. The x~2 test, Fisher's Exact Test, Nonparametric statistics test and Spearman correlation coefficient were used for the statistics, P<0.05 was considered significant. Result:1. In the 6 cell lines which were hypermethylated, sensitivity to BCNU was noted in 5 cell lines; in the 3 cell lines which were unmethylated, resistance to BCNU was noted in all of the 3 cell lines. Spearman correlation coefficient was used to analysis the result. The relation was significant, P <0.05.2. The rate of MGMT gene promotor methylation of glioma tissues in maleand female were 55.6%(10/18) and 44.4%(4/9), respectively. However, the difference was not significant, P>0.05; The rate of MGMT gene promotor methylation of paired serum in male and female were 50.0% (9/18) and 44.4% (4/9), respectively. However, the difference was not significant, P >0.05.3. The rate of hypermethylation of the promoter of MGMT gene of glioma tissues was 36.3%(4/l 1) in patients aged not more than 50 years; the rate of hypermethylation of the promoter of MGMT gene was 62.5%(10/16) in patient aged more than 50 years. The differences in methylation rate among
the both groups were not significant, />>0.05; The rate of hypermethylation of the promoter of MGMT gene of paired serum was 36.3%(4/l 1) in patients aged not more than 50 years; the rate of hypermethy lation of the promoter of MGMT gene was 56.2%(9/16) in patient aged more than 50 years. The differences in methylation rate among the both groups were not significant, P>0.05.4. Of the 27 glioma tissues, the methylation rate of MGMT in Grade I > Grade II > Grade III and Grade IV groups were 0.0% (0/2X 50.0% (5/10), 57.1% (8/14) and 100%, respectively. There were no significant differences among these groups, P>0.05; Of the 27 paired serum, the methylation rate of MGMT in Grade I ^ Grade II ^ Grade III and Grade IV groups were 0.0%(0/2X 40.0% (4/1 OX 57.1% (8/14) and 100%, respectively. There were no significant differences among these groups, P>0.05.5. Among the 27 glioma samples, MGMT expression was noted in 18 samples, in which hypermethylation was detected in 7(38.9%) cases, while MGMT expression was not noted in 9 samples, in which hypermethylation was detected in 7(77.8%) cases. Spearman correlation coefficient was used to analysis the result. The relation was significant, P<0.05.6. MGMT status was studied in DNA extracted from 27 glioma samples and paired serum samples. Among the 27 gliomas samples, MGMT hypermethylation was detected in 14(51.9%) cases, while it was detected in 13(48.1%) paired serum samples; MGMT unmethylation was detected in
13(48.1%) gliomas samples, while it was detected in 14(51.9%) pairedserum samples. Spearman correlation coefficient was used to analysis theresult. The relation was significant, P<0.05.Conclusion:The present study demonstrates that the aberrant methylation of MGMTgene promoter may play an important role in the sensibility of glioma toalkylating agents.1. In human glioma cell lines, the relation between the aberrant methylation of CpG islands in the promoter regions of MGMT gene promoter and the cell resistant to BCNU is significant. If the MGMT gene promoter is hypermethylated, the cell lines are sensitive to BCNU, while if the MGMT gene promoter is unmethylated, the cell lines are resistant to BCNU,2. The relationship between the aberrant methylation of MGMT gene promoter and the expression of MGMT in glioma is significant, so is the relationship between the aberrant methylation of MGMT gene promoter and the sensibility of glioma to alkylating agents, While the aberrant methylation of promoter of MGMT gene does not show any significant relationship with clinical condition such as age, gender and pathological grading.3. The relation between the aberrant methylation of promoter of MGMT gene in glioma tissues and paired serum is significant. Methylated MGMT is found in serum DNA of glioma patients, with a good correlation between serum and primary tumor tissue. Methylation-specific PCR assay in serum
DNA could be a good predictive tool for selecting glioma patients to be treated with alkylating agents.
引文
[1] Dolan ME, Schilsky RL. Silence is golden: gene hypermethylation and survival in large-cell lymphoma [J]. National Cancer Institute, 2002, 94(1): 6.
[2] Pegg A. Repair of O~6-alkylguainne by alkyltransferases [J]. Mutat Res, 2000, 462(2-3): 82.
[3] Bearzatto A, Szadkowski M, Macpherson P, et al. Epgenetic regulation of the MGMT and hMSH6 DNA repair genes in cells resistant to methylating agents [J]. Cancer Res, 2000, 60(12): 3262.
[4] Andratschke N, Grosu AL, Molls M, et al. Perspectives in the treatment of malignant gliomas in adults [J]. Anticancer Research, 2001, 21(5): 3541-3550.
[5] 章扬培.甲基转移酶与肿瘤耐药预见性、个体化化疗的研究[J].癌症,2004,23(6):724-734.
[6] Day RS 3rd, Ziolkowski CH, Scudiero DA, et al. Defective repair of alkylated DNA by human tumor and SV402transformed human cell strains [J]. Nature, 1980, 288: 724-727.
[7] Fornace AJ Jr, Papathanasiou MA, Hollander MC, et al. Expression of the O~6-methylguanine-DNA methyltransferase gene MGMT in MER~+ and MER~- human tumor cells [J]. Cancer Res, 1990, 50: 7908-7911.
[8] Pieper RO, Futscher BW, Dong Q, et al. Comparison of O~6-Methylguanine-DNA methyltransferase (MGMT) mRNA levels in Mer~+ and Mer~- human tumor cell lines containing the MGMT gene by the
??polymerase chain reaction technique [J]. Cancer Commun, 1990, 2:132-201
[9] Kroes RA, Erickson LC. The role of mRNA stability and transcription in O~6-methylguanine-DNA methyltransferase (MGMT) expression in Mer+ human tumor cells [J]. Carcinogenesis, 1995, 16:2255-2257.
[10] Dong SM, Pang JC, Poon WS, et al. Concurrent hypermethylation of multiple genes is associated with grade of oligodendroglial tumors [J]. J Neuropathol Exp Neurol, 2001, 60(8):808-816.
[11] Chen FY, Harris LC, Remack JS, et al. Cytoplasmic sequestration of an O~6-methylguanine-DNA methyltransferase enhancer binding protein in DNA repair-deficient human cells [J]. Proc Natl Acad sci, 1997, 94:4348-4353.
[12] Ali-osman F, Srivenugopal K, Sawaya R. The DNA-repair gene MGMT and the clinical response of gliomas to alkylating agents [J]. N Engl J Med, 2001,344:687.
[13] Leon SA , Shapiro B , Sklaroff DM, et al. Free DNA in the serum of cancer patients and the effect of therapy [J]. Cancer Res, 1977, 37(3):646 -650.
[14] Lee TL, Leung WK, Chan MW, et al. Detection of gene promoter hypermethylation in the tumor and serum of patients with gastric carcinoma [J]. Clin Cancer Res, 2002, 8(6): 1761 -1766.
[15] Carme B, Jose LR, Miquel T, et al. O~6-methyl-guanine-DNA methyltransferase Methylation in Serum and Tumor DNA Predicts Response to 1,3-Bis(2-Chloroethyl)-1-Nitrosourea but not to Temozolamide Plus
??Cisplatin in Glioblastoma Multiforme[J]. Clin Cancer Res.2003,9:1461-1468.
[16] Esteller M, Hamilton SR, Burger PC, Baylin SB, Herman JG. Inactivation of the DNA repair gene O~6-methylguanine-DNA methyltransferase by promoter hypermethylation is a common event in primary human neoplasia. Cancer Res, 1999 Feb 15; 59 (4): 793-7.
[17] Palmisano WA, Divine KK, Saccomanno G, et al. Predicting lung cancer by detecting aberrant promoter methylation in Sputum[J].Cancer Res,2000,60:5954-5958.
[18] Andratschke N, Grosu AL, Molls M, et al. Perspectives in the treatment of malignant gliomas in adults [J]. Anticancer Research, 2001, 21(5):3541-3550.
[19] Nutt CL, Loktionova NA, Pegg SE, et al. O~6-methylguanine DNA methyltransferase actifvity, p53 gene status and BCNU resistance in mouse astrocytes[J]. Carcinogenesis, 1999, 20(12):2361-2365.
[20] Bobola MS, Berger MS, Ellenbogen RG, et al. O~6-methylguanine DNA methyltransferase in pediatric primary brain tumors: relation to patients and tumor characteristics [J]. Clin Cancer Res, 2001, 7(3):613-619
[21] Silber JR, Bobola MS, Ghatan S, et al. O~6-methylguanine-DNA methyltransferase activity in adult gliomas: Relation to patient and tumor characteristics [J]. Cancer Research, 1998, 58(5): 1068-1073.
[22] Silber JR, Blank A, Bobola MS, et al. O~6-methylguanine DNA methyltransferase-deficient phenotype in human gliomas: frequency and time
to tumor progression after alkylating agent-based chemotherapy [J].Clin Cancer Res, 1999, 5(4): 807-814.
[23] Herman JG, Graff JR, Myohanen S, et al. Methylation-specific PCR: a novel PCR assay for methylation status of CpG islands. Proc Natl Acad Sci U S A, 1996 Sep 3; 93 (18): 9821-6.
[24] 赵迎社,张思仲.改进的甲基化特异PCR法在抑癌基因P16检测中的应用.中华医学遗传学杂志,1999,16(5):334-336.
[25] 南克俊,魏永长.肿瘤患者血清DNA甲基化的研究进展[J].癌变·畸变·突变,2003,15(4):249-254.
[26] Mattem J, Eichom U, Kaina B, et al. O~6-methylguanine DNA methyltransferase activity and sensitivity to cyclophosphamide and cisplatin in human lung tumor xenografts[J]. Int J Cancer, 1998, 77: 919-922
[27] Esteller M, Hamilton SR, Burger PC, et al. Inactivation of the DNA repair gene O~6-methylguanine-DNA methyltransferase by promoter hypermethylation is a common event in primary human neoplasia [J]. Cancer Research, 1999, 59(4): 793-797.
[28] Balana C, Ramirez JL, Taron M, et al. O~6-methyl-guanine-DNA methyltransferase Methylation in Serum and Tumor DNA Predicts Response to 1,3-Bis(2-Chloroethyl)-1-Nitrosourea but not to Temozolamide Plus Cisplatin in Glioblastoma Multiforme [J]. Clin Cancer Res, 2003, 9(4): 1464-1468.
[29] Esteller M, Garcia-Foncillas J, Andion E, et al. Inactivation of the DNA-Repair Gene MGMT and the Clinical Response of Gliomas to Alkylating Agents[J].N Engl Med,2000,343(23): 1350-1354.
[30] Hegi ME, Diserens AC, Gorlia T, et al. MGMT Gene Silencing and Benefit from Temozolomide in Glioblastoma[J]. N Engl Med. 2005, 352(10): 997-1003.
[31] 孙彦辉,张亚卓,王忠诚等.MGMT在脑胶质瘤组织中的表达及其与患者生存期的关系[J].癌症,2004,23(9),1052-1055.
[2] Pegg A. Repair of O~6-alkylguainne by alkyltransferases [J]. Mutat Res, 2000, 462(2-3): 82.
[3] Bearzatto A, Szadkowski M, Macpherson P, et al. Epgenetic regulation of the MGMT and hMSH6 DNA repair genes in cells resistant to methylating agents [J]. Cancer Res, 2000, 60(12): 3262.
[4] Andratschke N, Grosu AL, Molls M, et al. Perspectives in the treatment of malignant gliomas in adults [J]. Anticancer Research, 2001, 21(5): 3541-3550.
[5] 章扬培.甲基转移酶与肿瘤耐药预见性、个体化化疗的研究[J].癌症,2004,23(6):724-734.
[6] Day RS 3rd, Ziolkowski CH, Scudiero DA, et al. Defective repair of alkylated DNA by human tumor and SV402transformed human cell strains [J]. Nature, 1980, 288: 724-727.
[7] Fornace AJ Jr, Papathanasiou MA, Hollander MC, et al. Expression of the O~6-methylguanine-DNA methyltransferase gene MGMT in MER~+ and MER~- human tumor cells [J]. Cancer Res, 1990, 50: 7908-7911.
[8] Pieper RO, Futscher BW, Dong Q, et al. Comparison of O~6-Methylguanine-DNA methyltransferase (MGMT) mRNA levels in Mer~+ and Mer~- human tumor cell lines containing the MGMT gene by the
??polymerase chain reaction technique [J]. Cancer Commun, 1990, 2:132-201
[9] Kroes RA, Erickson LC. The role of mRNA stability and transcription in O~6-methylguanine-DNA methyltransferase (MGMT) expression in Mer+ human tumor cells [J]. Carcinogenesis, 1995, 16:2255-2257.
[10] Dong SM, Pang JC, Poon WS, et al. Concurrent hypermethylation of multiple genes is associated with grade of oligodendroglial tumors [J]. J Neuropathol Exp Neurol, 2001, 60(8):808-816.
[11] Chen FY, Harris LC, Remack JS, et al. Cytoplasmic sequestration of an O~6-methylguanine-DNA methyltransferase enhancer binding protein in DNA repair-deficient human cells [J]. Proc Natl Acad sci, 1997, 94:4348-4353.
[12] Ali-osman F, Srivenugopal K, Sawaya R. The DNA-repair gene MGMT and the clinical response of gliomas to alkylating agents [J]. N Engl J Med, 2001,344:687.
[13] Leon SA , Shapiro B , Sklaroff DM, et al. Free DNA in the serum of cancer patients and the effect of therapy [J]. Cancer Res, 1977, 37(3):646 -650.
[14] Lee TL, Leung WK, Chan MW, et al. Detection of gene promoter hypermethylation in the tumor and serum of patients with gastric carcinoma [J]. Clin Cancer Res, 2002, 8(6): 1761 -1766.
[15] Carme B, Jose LR, Miquel T, et al. O~6-methyl-guanine-DNA methyltransferase Methylation in Serum and Tumor DNA Predicts Response to 1,3-Bis(2-Chloroethyl)-1-Nitrosourea but not to Temozolamide Plus
??Cisplatin in Glioblastoma Multiforme[J]. Clin Cancer Res.2003,9:1461-1468.
[16] Esteller M, Hamilton SR, Burger PC, Baylin SB, Herman JG. Inactivation of the DNA repair gene O~6-methylguanine-DNA methyltransferase by promoter hypermethylation is a common event in primary human neoplasia. Cancer Res, 1999 Feb 15; 59 (4): 793-7.
[17] Palmisano WA, Divine KK, Saccomanno G, et al. Predicting lung cancer by detecting aberrant promoter methylation in Sputum[J].Cancer Res,2000,60:5954-5958.
[18] Andratschke N, Grosu AL, Molls M, et al. Perspectives in the treatment of malignant gliomas in adults [J]. Anticancer Research, 2001, 21(5):3541-3550.
[19] Nutt CL, Loktionova NA, Pegg SE, et al. O~6-methylguanine DNA methyltransferase actifvity, p53 gene status and BCNU resistance in mouse astrocytes[J]. Carcinogenesis, 1999, 20(12):2361-2365.
[20] Bobola MS, Berger MS, Ellenbogen RG, et al. O~6-methylguanine DNA methyltransferase in pediatric primary brain tumors: relation to patients and tumor characteristics [J]. Clin Cancer Res, 2001, 7(3):613-619
[21] Silber JR, Bobola MS, Ghatan S, et al. O~6-methylguanine-DNA methyltransferase activity in adult gliomas: Relation to patient and tumor characteristics [J]. Cancer Research, 1998, 58(5): 1068-1073.
[22] Silber JR, Blank A, Bobola MS, et al. O~6-methylguanine DNA methyltransferase-deficient phenotype in human gliomas: frequency and time
to tumor progression after alkylating agent-based chemotherapy [J].Clin Cancer Res, 1999, 5(4): 807-814.
[23] Herman JG, Graff JR, Myohanen S, et al. Methylation-specific PCR: a novel PCR assay for methylation status of CpG islands. Proc Natl Acad Sci U S A, 1996 Sep 3; 93 (18): 9821-6.
[24] 赵迎社,张思仲.改进的甲基化特异PCR法在抑癌基因P16检测中的应用.中华医学遗传学杂志,1999,16(5):334-336.
[25] 南克俊,魏永长.肿瘤患者血清DNA甲基化的研究进展[J].癌变·畸变·突变,2003,15(4):249-254.
[26] Mattem J, Eichom U, Kaina B, et al. O~6-methylguanine DNA methyltransferase activity and sensitivity to cyclophosphamide and cisplatin in human lung tumor xenografts[J]. Int J Cancer, 1998, 77: 919-922
[27] Esteller M, Hamilton SR, Burger PC, et al. Inactivation of the DNA repair gene O~6-methylguanine-DNA methyltransferase by promoter hypermethylation is a common event in primary human neoplasia [J]. Cancer Research, 1999, 59(4): 793-797.
[28] Balana C, Ramirez JL, Taron M, et al. O~6-methyl-guanine-DNA methyltransferase Methylation in Serum and Tumor DNA Predicts Response to 1,3-Bis(2-Chloroethyl)-1-Nitrosourea but not to Temozolamide Plus Cisplatin in Glioblastoma Multiforme [J]. Clin Cancer Res, 2003, 9(4): 1464-1468.
[29] Esteller M, Garcia-Foncillas J, Andion E, et al. Inactivation of the DNA-Repair Gene MGMT and the Clinical Response of Gliomas to Alkylating Agents[J].N Engl Med,2000,343(23): 1350-1354.
[30] Hegi ME, Diserens AC, Gorlia T, et al. MGMT Gene Silencing and Benefit from Temozolomide in Glioblastoma[J]. N Engl Med. 2005, 352(10): 997-1003.
[31] 孙彦辉,张亚卓,王忠诚等.MGMT在脑胶质瘤组织中的表达及其与患者生存期的关系[J].癌症,2004,23(9),1052-1055.