Stirewalt D L, Pogosova-Agadjanyan E L, Tsuchiya K, Joaquin J, Meshinchi S
Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA.
1] Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA [2] Department of Pathology, Seattle Children's Hospital, Seattle, WA, USA [3] Department of Laboratory Medicine, University of Washington Medical Center, Seattle, WA, USA.
Blood Cancer J. 2014 May 2;4(5):e208. doi: 10.1038/bcj.2014.27.
Patients with high FLT3 internal tandem duplication allelic ratios (FLT3/ITD-ARs) have a poor prognosis. Single-nucleotide polymorphism/comparative genomic hybridization, single-cell PCR and colony-forming assays were used to evaluate genotypic evolution of high FLT3/ITD-ARs in 85 acute myeloid leukemia (AML) patients. Microarrays were used to examine molecular pathways disrupted in leukemic blasts with high FLT3/ITD-ARs. Copy-neutral loss of heterozygosity (CN-LOH) was identified at the FLT3 locus in diagnostic samples with high FLT3/ITD-ARs (N=11), but not in samples with low FLT3/ITD-ARs (N=24), FLT3-activating loop mutations (N=11) or wild-type FLT3 (N=39). Single-cell assays showed that homozygous FLT3/ITD genotype was present in subsets of leukemic blasts at diagnosis but became the dominant clone at relapse. Less differentiated CD34(+)/CD33(-) progenitor colonies were heterozygous for FLT3/ITD, whereas more differentiated CD34(+)/CD33(+) progenitor colonies were homozygous for FLT3/ITD. Expression profiling revealed that samples harboring high FLT3/ITD-ARs aberrantly expressed genes within the recombination/DNA repair pathway. Thus, the development of CN-LOH at the FLT3 locus, which results in high FLT3/ITD-ARs, likely represents a late genomic event that occurs after the acquisition of the FLT3/ITD. Although the etiology underlying the development of CN-LOH remains to be clarified, the disruption in recombination/DNA repair pathway, which is present before the development of LOH, may have a role.
FLT3内部串联重复等位基因比率（FLT3/ITD-ARs）高的患者预后较差。采用单核苷酸多态性/比较基因组杂交、单细胞PCR和集落形成试验评估85例急性髓系白血病（AML）患者中高FLT3/ITD-ARs的基因型演变。利用微阵列检测高FLT3/ITD-ARs的白血病原始细胞中被破坏的分子途径。在诊断时FLT3/ITD-ARs高的样本（N=11）中，FLT3基因座处鉴定出杂合性拷贝中性缺失（CN-LOH），但在FLT3/ITD-ARs低的样本（N=24）、FLT3激活环突变样本（N=11）或野生型FLT3样本（N=39）中未发现。单细胞试验表明，白血病原始细胞亚群在诊断时存在纯合FLT3/ITD基因型，但在复发时成为优势克隆。分化程度较低的CD34(+)/CD33(-)祖细胞集落对于FLT3/ITD是杂合的，而分化程度较高的CD34(+)/CD33(+)祖细胞集落对于FLT3/ITD是纯合的。表达谱分析显示，携带高FLT3/ITD-ARs的样本在重组/DNA修复途径内异常表达基因。因此，FLT3基因座处CN-LOH的发生导致高FLT3/ITD-ARs，这可能代表在获得FLT3/ITD之后发生的晚期基因组事件。虽然CN-LOH发生的病因仍有待阐明，但在LOH发生之前就存在的重组/DNA修复途径的破坏可能起了作用。
