巯基嘌呤甲基转移酶活性和硫鸟嘌呤核苷酸浓度检测在6-MP个体化化疗中的意义

Significance of TPMT activity and TGNs level detection for individualizing 6-mercaptopurine chemotherapy

目的 探讨巯基嘌呤甲基转移酶 (TPMT)活性、基因型和硫鸟嘌呤核苷酸 (TGNs)浓度检测对 6 巯基嘌呤 (6 MP)化疗个体化的意义。方法 用放射性核素标记方法测定红细胞TPMT活性 ,用特异引物序列 PCR和限制性片段长度多态性 PCR方法检测低活性者的基因型 ,通过高效液相色谱法(HPLC)检测急性淋巴细胞白血病 (ALL)患儿在服用 6 MP后红细胞内的TGNs浓度。结果 371名受检者的平均TPMT活性为 (16 .6± 4.5 )U mlpRBCs ,其中≤ 10U mlpRBCs的低活性比例为 8.1%,男性和女性的平均TPMT活性分别为 (16 .8± 5 .0 )U mlpRBCs和 (16 .5± 4.4)U mlpRBCs ,汉族人TPMT活性不存在性别、年龄差异 ,健康志愿者与白血病患儿之间差异亦无显著性 ;30名TPMT活性低下者的DNA中包括TPMT 2型 5例 ,TPMT 3A型 4例 ,TPMT 3B型 6例 ,TPMT 3C型 10例 ,另有 5例未出现上述基因型 ;ALL患儿治疗前红细胞TPMT活性与服用 6 MP 7～ 14d的红细胞内TGNs稳态浓度呈负相关。TGNs浓度与测定后第 14天的白细胞计数呈负相关。结论 服用 6 MP前测定TPMT活性和服药时监测TGNs浓度能够有助于预防抗嘌呤代谢药物的不良反应 ,指导其化疗个体化 ,改善疗效。

Objective To evaluate the activity and genotype of thiopurine methyltransferase (TPMT) and the concentration of thioguanine nucleotides (TGNs) as parameters for individualizing mercaptopurine (6-MP) therapy. Methods Erythrocyte TPMT activity was measured by means of radiochemical assay. Sequence specific primer(SSP) PCR and restriction fragment length polymorphism(RFLP)- were used to determine the mutations in TPMT genomic DNAs. Erythrocyte TGNs concentration in acute lymphoblastic leukemia (ALL) patients after 6-MP treatment was detected by high-performance liquid chromatography (HPLC). Results The erythrocyte TPMT activity in Han population was 16.6±4.5U/ml pRBCs (man 16.8±5.0 U/ml pRBCs, woman 16.5±4.4 U/ml pRBCs), the activity in 8.1% of the samples was lower than 10 U/ml pRBCs. There was no difference for TPMT activity by gender, age, and between healthy donors and ALL patients. For TPMT genotypes, there were 5 cases of TPMT*2,4 TPMT*3A,6 TPMT*3B, 10 TPMT*3C and 5 unknown in 30 subjects who had low TPMT activity. In children with ALL, the TGNs level did show a negative correlation with TPMT activity at diagnosis and 7～14 days after 6-MP therapy and with WBC count 14 days after the determination of TGNs. Conclusion Detection of TPMT activity before 6-MP therapy and TGNs level during 6-MP therapy may be helpful for preventing side effects from antipurine metabolic drug overdose, and individualizing 6-MP chemotherapy in children with ALL.