急性T淋巴细胞白血病微小残留病实时荧光定量聚合酶链反应检测的意义

A tal-1 deletion as real-time quantitative polymerase chain reaction target for detection of minimal residual disease in T-lineage acute lymphoblastic leukemia

目的 研究采用实时荧光定量聚合酶链反应 (RQ-PCR)技术检测具有tal-1缺失的急性T淋巴细胞白血病(T ALL)患儿骨髓微小残留病 (MRD)水平的可行性,并探讨不同时间点MRD水平在预后和临床治疗干预上的意义。方法 采用最常见的tal 1缺失断裂点sildb1-tal1db1,对 50例T-ALL患儿初治标本进行阳性筛选;应用RQ-PCR技术检测所有阳性患儿初治标本的敏感度,并对这些患儿化疗达完全缓解(CR)及其后不同时间点的骨髓标本进行MRD定量检测,并以极限稀释法检测结果进行比较;对上述两种方法分别检测出的结果进行相关回归分析。结果 ( 1 )在 50例T-ALL患儿中,共检测出 10例阳性患儿; (2)采用RQ-PCR技术和极限稀释法分别检测患儿CR期及其后各个时间点的 28份标本,有 24份标本两种方法检测结果均大于 10-5,两种方法检测结果的相关性很好(r=0 898,P<0.001); (3)在规律治疗的 8例患儿中,CR时骨髓MRD水平高于 10-4的 3例患儿皆在化疗过程中复发,而低于 10-4的 5例一直未复发。结论 RQ-PCR技术是一项特异性强,重现性好、精确快速的MRD定量检测手段。不同时间点的MRD水平升高对预后的意义不同,对及时调整治疗方案、改善预后有重要价值。

Objective Hematologic relapse remains the greatest obstacle to the cure of acute lymphoblastic leukemia (ALL), especially T-lineage acute lymphoblastic leukemia (T-ALL) in children. Recent studies have shown that patients with increased risk of relapse can be identified by measuring residual leukemic cells, called minimal residual disease (MRD), during clinical remission. Current polymerase chain reaction(PCR) methods, however, for measuring MRD are cumbersome and time-consuming. To improve and simplify MRD assessment, the author developed a real-time quantitative PCR (RQ-PCR) assay for the detection of leukemic cells that harbor the tal-1 deletion. In addition, the author discussed the significance of MRD levels at different stages in treatment and prognosis of children with T-ALL. Methods(A total) of 50 consecutively enrolled patients with T-ALL were analysed for detection of leukemic cells harboring the most common tal-1 deletion. Serial dilutions of leukemic DNA were studied to find the sensitivity of detection with RQ-PCR assay. The MRD of 28 samples in clinical remission from 10 patients were quantified by RQ-PCR assay and limiting dilution assay. The results detected by both methods were compared statistically with correlation analysis.Results (1) A total of 10 patients presented tal-1 deletion involving the sildb1 breakpoint rearranged to tal1db1 in 50 cases with T-ALL. The breakpoints of relapsed samples are the same as those of the corresponding diagnostic samples; (2) The RQ-PCR assay had a sensitivity of detection of one leukemic cell among 100 000 normal cells. In 24 samples, MRD levels>10^(-5) could be detected with both methods. The percentages of leukemic cells measured by the two methods correlated well (r=0.898, P<0.001); (3)The MRD levels of 3 patients out of the 8 cases undergoing disciplinary regimen were over 10^(-4) at the end of induction chemotherapy. They all relapsed in bone marrow during chemotherapy. The higher the MRD levels, the earlier the replapse. The other 5 patients with MRD levels<10^(-4) had been relapse-free survival(RFS) for 4-59 months, one of whom with increased MRD levels>10^(-4) for twice at the continuation stage had been RFS for 27 months till now.Conclusions The sildb1-taldb1 deletion presents in 20% of T-ALL, and is an ideal PCR marker for its specificity, uniform and stability; The tal-1 RQ-PCR can be used for the rapidly, sensitively and accurately quantitative assessment of MRD in T-ALL with the tal-1 deletion. MRD levels at different stages of chemotherapy have different significance in prognosis and treatment.