BackgroundAcute myeloid leukemia (AML) is characterized by clonal heterogeneity, leading to frequent relapses and drug resistance despite intensive clinical therapy. Although AML's clonal architecture has been addressed in many studies, practical monitoring of dynamic changes in those subclones during relapse and treatment is still understudied.MethodFifteen longitudinal bone marrow (BM) samples were collected from three relapsed and refractory (R/R) AML patients. Using droplet digital polymerase chain reaction (ddPCR), the frequencies of patient's leukemic variants were assessed in seven cell populations that were isolated from each BM sample based on cellular phenotypes. By quantifying mutant clones at the diagnosis, remission, and relapse stages, the distribution of AML subclones was sequentially monitored.ResultsMinimal residual (MR) leukemic subclones exhibit heterogeneous distribution among BM cell populations, including mature leukocyte populations. During AML progression, these subclones undergo active phenotypic transitions and repopulate into distinct cell population regardless of normal hematopoiesis hierarchic order. Of these, MR subclones in progenitor populations of patient BM predominantly carry MR leukemic properties, leading to more robust expansion and stubborn persistence than those in mature populations. Moreover, a minor subset of MR leukemic subclones could be sustained at an extremely low frequency without clonal expansion during relapse.ConclusionsIn this study, we observed treatment persistent MR leukemic subclones and their phenotypic changes during the treatment process of R/R AML patients. This underscores the importance of preemptive inhibition of clonal promiscuity in R/R AML, proposing a practical method for monitoring AML MR subclones.

中文翻译：

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常规治疗期间复发难治性急性髓系白血病最小残留白血病亚克隆的动态研究

背景急性髓系白血病（AML）具有克隆异质性的特点，尽管经过强化的临床治疗，仍会导致频繁的复发和耐药性。尽管许多研究已经解决了 AML 的克隆结构，但对这些亚克隆在复发和治疗过程中动态变化的实际监测仍在研究中。方法从三名复发难治性 (R/R) AML 患者中收集了 15 个纵向骨髓 (BM) 样本。使用液滴数字聚合酶链式反应 (ddPCR)，根据细胞表型从每个 BM 样本中分离出七个细胞群，评估患者白血病变异的频率。通过量化诊断、缓解和复发阶段的突变克隆，连续监测 AML 亚克隆的分布。结果最小残留 (MR) 白血病亚克隆在 BM 细胞群（包括成熟白细胞群）中表现出异质分布。在 AML 进展过程中，这些亚克隆经历活跃的表型转变，并重新填充为不同的细胞群，无论正常的造血层次顺序如何。其中，患者 BM 祖细胞群中的 MR 亚克隆主要携带 MR 白血病特性，导致比成熟群体中的那些更强劲的扩张和顽固的持久性。此外，一小部分MR白血病亚克隆可以以极低的频率持续存在，在复发期间不会出现克隆扩增。结论在本研究中，我们观察了R/R AML患者治疗过程中持续存在的MR白血病亚克隆及其表型变化。这强调了在 R/R AML 中抢先抑制克隆混乱的重要性，提出了一种监测 AML MR 亚克隆的实用方法。