实时定量RT-PCR检测急性早幼粒细胞白血病PML-RARa融合基因

Detection of PML/RARa Transcripts in Acute Promyelocytic Leukemia by Real-time Quantitative Reverse Transcription Polymerase Chain Reaction

本研究旨在建立用实时定量RT-PCR检测急性早幼粒细胞白血病(APL)PML-RARa mRNA的方法,探讨APLPML-RARa融合基因表达水平与疗效的关系。用RT-PCR扩增培养的NB4细胞的PML-RARa融合基因,取1μgNB4细胞的总cDNA进行10倍的梯度稀释,作为标准品,建立荧光定量RT-PCR方法,对方法的灵敏性、稳定性、重复性进行了测定。定量检测4例急性早幼粒细胞白血病(APL)患者治疗前后骨髓内PML-RARa融合基因转录本水平,并对1例经治疗完全缓解后又复发的患者PML-RARa转录本水平(拷贝数)进行动态监测。结果表明:用本研究建立的实时定量RT-PCR方法可检测出10-5μgNB4细胞cDNA中的PML-RARa融合基因,其重复性的CT值,管间、批间变异系数(CV)分别为2.1%、3.8%。4例患者初治骨髓PML-RARa基因转录本水平的分别为1884、5533、1803、4677拷贝,平均为3475拷贝。经ATRA+化疗治疗后其PML-RARa基因转录水平下降至40、135、79、229拷贝,平均为121拷贝。还有1例患者治疗前PML-RARa基因转录本水平为8600拷贝,经过4个月治疗,虽然此时患者处于完全缓解期,但其转录水平拷贝数仍有730。3个月后患者出现复发,转录本水平升至为11000拷贝。经过ATRA+化疗治疗后转录本水平又逐渐下降至1200拷贝。结论;建立的实时定量RT-PCR灵敏、重复性好。治疗后APL患者的PML-RARa融合基因转录本水平明显下降,复发时基因转录本水平又升高。融合基因表达水平的改变与临床疾病进展关系一致,这有助于监测白血病微小残留病,评价疗效及判断预后。

Tihs study was purposed to establish a real-time quantitative reverse transcription polymerase chain reaction （RT-PCR） for detection of PML/RARa fusion gene in patients with acute promyelocytic leukemia （APL） and to explore the relationship between the expression level of PML/RARa fusion gene transcript and the clinical status or efficacy of the therapy in APL. The conventional RT-PCR was used to amplify PML/RARa gene from cultured NB4 cells. Standard curves were constructed by modified real-time PCR on standard template after 10-fold serial dilutions of cDNA of 1 μg NB4 cells. The sensitivity, stability and repeatability of this method was determined. The PML/RARa gene transcripts of bone marrows in 4 APL patients before and after treatment and in 1 APL patient relapsed after complete remission were dynamically detected by modified real-time quantitative RT-PCR. The results indicated that the sensitivity of real-time quantitative RT-PCR for detecting PML/RARa fusion gene was about 10^-5 μg cDNA from NB4 cells, the repeatability and reproducibility of this method were satisfactory, intra-and inter-assay coefficients of variation were 2.1% and 3.8%. The copy numbers of PML/RARa transcripte reflecting PML/RARa fusion gene expression level in 4 newly diagnosed patients with APL were 1884, 5533, 1803, 4677 and the median was 3 475. After ATRA ＋ chemotherapy copy numbers of PML/RARa transcript decreased to 40, 135, 79, 29, and mean was 121. Another patient＇s PML/RARa gene copy number was 8600 at diagnosis, the gene copy number was 730 after therapy for 4 months, although he was in complete remission, but copy number increased to 11 000 when APL relapsed 3 months later. The copy number efficiently reduced to 1200 after ATRA ＋ chemotherapy. It is concluded that the established realreal-time quantitative RT-PCR method is sensitive, reliable, accurate and repeatable. The efficiency of method was finally tested for patient samples, showing a PML/RARa transcript copy number in APL patients significantly decrease after therapy, and increase at the time of relapse which indicate that changes of fusion gene expression levels coincide with clinical progress of disease. This method can be used to detect the minimal residual disease, assess response to treatment and evaluate prognosis of disease.