Grimwade D, Howe K, Langabeer S, Davies L, Oliver F, Walker H, Swirsky D, Wheatley K, Goldstone A, Burnett A, Solomon E
Somatic Cell Genetics Laboratory, Imperial Cancer Research Fund, London.
Br J Haematol. 1996 Sep;94(3):557-73.
Detection of the t(15;17) or its molecular consequence, the PML-RAR alpha rearrangement, is critical for meaningful analysis of clinical trials involving patients with suspected acute promyelocytic leukaemia (APL). Its presence remains the best predictor of a favourable response to retinoids, such as ATRA, which in combination with chemotherapy confer significant improvements in disease-free survival. We have evaluated the relative efficacy of RT-PCR, cytogenetics and PML immunofluorescence staining to identify the existence of the translocation in 100 patients entered into the Medical Research Council (M.R.C.) ATRA trial. RT-PCR successfully identified PML-RAR alpha rearrangements in 93/100 patients, including 65 where only peripheral blood or post-induction marrow samples were available for analysis and in 12 patients in whom cytogenetic assessment failed to demonstrate t(15;17) due to poor-quality metaphases (10/12) or as a reflection of cryptic PML-RAR alpha rearrangements (2/12). Parallel employment of the RAR alpha-PML assay confirmed expression of del(17q)-derived transcripts in 81% and permitted determination of the PML breakpoint (a potential independent prognostic variable) in all 93 cases. Sequencing of RT-PCR products derived from 50 patients with 3' PML breakpoints revealed five bcr 2 cases, including a novel exon 5 breakpoint. 35/81 (43%) patients with cytogenetic evidence of t(15;17) possessed additional karyotypic abnormalities. In four patients with available buffy coat smears, lack of cytogenetic or molecular evidence of the t(15;17) was confirmed by a wild-type PML immunofluorescence nuclear staining pattern, in contrast to the characteristic microparticulate distribution detected in 14 patients with RT-PCR evidence of the rearrangement. However, although PML immunofluorescence staining is suitable for rapid determination of patients likely to benefit from ATRA, this approach does not obviate the need for cytogenetic and RT-PCR analysis of all patients entered into APL clinical trials, because both techniques provide additional information which may prove to be of independent prognostic significance.
检测t(15;17)或其分子学结果即PML-RARα重排，对于涉及疑似急性早幼粒细胞白血病（APL）患者的临床试验进行有意义的分析至关重要。其存在仍然是对维甲酸（如全反式维甲酸，ATRA）产生良好反应的最佳预测指标，ATRA与化疗联合使用可显著提高无病生存率。我们评估了逆转录聚合酶链反应（RT-PCR）、细胞遗传学和PML免疫荧光染色在确定参与医学研究委员会（M.R.C.）ATRA试验的100例患者中该易位存在情况的相对效能。RT-PCR成功在93/100例患者中鉴定出PML-RARα重排，其中包括65例仅有外周血或诱导后骨髓样本可供分析的患者，以及12例因中期相质量差（10/12）或作为隐匿性PML-RARα重排的反映（2/12）而细胞遗传学评估未能证实t(15;17)的患者。同时采用RARα-PML检测法证实81%的患者中存在源自del(17q)的转录本表达，并在所有93例病例中确定了PML断点（一个潜在的独立预后变量）。对50例具有3' PML断点的患者的RT-PCR产物进行测序，发现5例bcr 2病例，包括一个新的外显子5断点。35/81（43%）具有t(15;17)细胞遗传学证据的患者存在额外的核型异常。在4例有血沉棕黄层涂片的患者中，野生型PML免疫荧光核染色模式证实缺乏t(15;17)的细胞遗传学或分子学证据，与之形成对比的是，在14例有RT-PCR重排证据的患者中检测到特征性的微粒分布。然而，尽管PML免疫荧光染色适用于快速确定可能从ATRA中获益的患者，但这种方法并不能消除对所有参与APL临床试验患者进行细胞遗传学和RT-PCR分析的必要性，因为这两种技术都能提供可能具有独立预后意义的额外信息。
