Bose S, Deininger M, Gora-Tybor J, Goldman J M, Melo J V
LRF Centre for Adult Leukaemia, Department of Haematology, Imperial College School of Medicine, Hammersmith Hospital, London, UK.
Blood. 1998 Nov 1;92(9):3362-7.
The number of genetic lesions necessary to generate leukemia in humans is unknown, but it is possible that certain specific abnormalities, eg, fusion genes, known to be associated with acute and chronic leukemia are produced relatively frequently in human cells but require other events to occur before the leukemia becomes manifest. We investigated this possibility by studying peripheral blood leukocytes from normal individuals and various hematopoietic cell lines for the presence and expression of the p210 and the p190 types of the BCR-ABL gene associated with chronic myeloid leukemia (CML) and acute lymphoblastic leukemia. We used two-step reverse transcriptase-polymerase chain reaction (RT-PCR) assays in which batches of 10(8) cells per sample were tested in 40 replicate reactions. We estimate that this assay is 1.5 logs more sensitive than the two-step RT-PCR assays that we use routinely to assess minimal residual disease. BCR-ABL fusion gene transcripts of various configurations were found in circulating leukocytes from 12 of the 16 healthy adults analyzed. Transcripts with an e1a2 junction (p190 BCR-ABL) were present in 11 and p210-type transcripts with b2a2 and/or b3a2 junctions were detected in 4 individuals. The same RT-PCR assays in non-CML cell lines showed the presence of classical or aberrant p210-type mRNA in 3 of 7 lines and of p190-type transcripts in all 7 lines of hematopoietic origin (HL60, KG1, U937, Kasumi, Jurkat, JVM13, and JVM25), whereas the NIH3T3 murine fibroblast line was reproducibly negative for these fusion genes. These findings confirm and extend previous reports on the detection of leukemia-associated genes in normal leukocytes and suggest that certain fusion genes are generated relatively frequently in hematopoietic cells, but only infrequently do the cells acquire the additional changes necessary to produce leukemia in humans. Although there is only a small probability that such innocent BCR-ABL-carrying leukocytes are detected by conventional RT-PCR assays, they may be the source of some sporadically positive tests in leukemia patients in long-term remission.
引发人类白血病所需的基因损伤数量尚不清楚，但有可能某些特定的异常情况，例如已知与急慢性白血病相关的融合基因，在人类细胞中相对频繁地产生，但在白血病显现之前还需要其他事件发生。我们通过研究正常个体的外周血白细胞和各种造血细胞系，来调查这种可能性，检测其中与慢性粒细胞白血病（CML）和急性淋巴细胞白血病相关的p210和p190类型的BCR-ABL基因的存在和表达情况。我们使用了两步逆转录聚合酶链反应（RT-PCR）检测方法，每个样本中每批10⁸个细胞在40次重复反应中进行检测。我们估计该检测方法比我们常规用于评估微小残留病的两步RT-PCR检测方法灵敏度高1.5个对数级。在分析的16名健康成年人中，有12人的循环白细胞中发现了各种构型的BCR-ABL融合基因转录本。11人存在具有e1a2连接（p190 BCR-ABL）的转录本，4人检测到具有b2a2和/或b3a2连接的p210型转录本。在非CML细胞系中进行的相同RT-PCR检测显示，7个细胞系中有3个存在经典或异常的p210型mRNA，所有7个造血来源的细胞系（HL60、KG1、U937、Kasumi、Jurkat、JVM13和JVM25）中都存在p190型转录本，而NIH3T3小鼠成纤维细胞系对这些融合基因始终呈阴性。这些发现证实并扩展了先前关于在正常白细胞中检测白血病相关基因的报道，表明某些融合基因在造血细胞中相对频繁地产生，但细胞很少获得在人类中产生白血病所需的额外变化。尽管通过传统RT-PCR检测方法检测到这种携带BCR-ABL的无辜白细胞的可能性很小，但它们可能是长期缓解的白血病患者中一些偶尔出现阳性检测结果的来源。
