Data_Sheet_1_The Second Oncogenic Hit Determines the Cell Fate of ETV6-RUNX1 Positive Leukemia.pdf

ETV6-RUNX1 is almost exclusively associated with childhood B-cell acute lymphoblastic leukemia (B-ALL), but the consequences of ETV6-RUNX1 expression on cell lineage decisions during B-cell leukemogenesis are completely unknown. Clinically silent ETV6-RUNX1 preleukemic clones are frequently found in neonatal cord blood, but few carriers develop B-ALL as a result of secondary genetic alterations. The understanding of the mechanisms underlying the first transforming steps could greatly advance the development of non-toxic prophylactic interventions. Using genetic lineage tracing, we examined the capacity of ETV6-RUNX1 to instruct a malignant phenotype in the hematopoietic lineage by cell-specific Cre-mediated activation of ETV6-RUNX1 from the endogenous Etv6 gene locus. Here we show that, while ETV6-RUNX1 has the propensity to trigger both T- and B-lymphoid malignancies, it is the second hit that determines tumor cell identity. To instigate leukemia, both oncogenic hits must place early in the development of hematopoietic/precursor cells, not in already committed B-cells. Depending on the nature of the second hit, the resulting B-ALLs presented distinct entities that were clearly separable based on their gene expression profiles. Our findings give a novel mechanistic insight into the early steps of ETV6-RUNX1+ B-ALL development and might have major implications for the potential development of ETV6-RUNX1+ B-ALL prevention strategies.

ETV6-RUNX1与儿童B细胞急性淋巴细胞白血病（B-ALL）几乎具有唯一相关性，然而，ETV6-RUNX1在B细胞白血病发生过程中对细胞谱系决策的影响尚完全未知。ETV6-RUNX1前白血病克隆在新生儿脐带血中常呈临床隐匿状态，但携带者中仅有少数因次级基因变异而发展为B-ALL。对导致首次转化步骤的机制的理解，将极大推动非毒性预防干预措施的开发。通过遗传谱系追踪，我们考察了ETV6-RUNX1通过Cre介导的细胞特异性激活，从内源性Etv6基因位点的细胞特异激活，指导造血谱系中恶性表型的能力。本研究表明，尽管ETV6-RUNX1具有引发T和B淋巴系恶性肿瘤的倾向，但肿瘤细胞身份的决定在于第二次打击。要引发白血病，两种致癌打击必须在造血/前体细胞发育的早期阶段发生，而不是在已经分化的B细胞中。根据第二次打击的性质，由此产生的B-ALL表现出不同的实体，这些实体根据其基因表达谱可以明显区分。我们的发现为ETV6-RUNX1+ B-ALL发展的早期步骤提供了新的机制性见解，并可能对ETV6-RUNX1+ B-ALL预防策略的开发具有重大意义。