Cre-recombinase expression cooperates with FLT3ITD/ITD to induce acute myeloid leukemia [RNASeq_SclCre_BM]. Cre-recombinase expression cooperates with FLT3ITD/ITD to induce acute myeloid leukemia [RNASeq_SclCre_BM]

Animal models offer a valuable tool to recapitulate genetically defined subtypes of AML, and to assess the potential of compound mutations and clonal evolution during disease progression. This is of utmost importance for difficult to treat leukemias such as FLT3-ITD positive AML. While conditional gene targeting by Cre-recombinase is a powerful technology that has revolutionized biomedical research, consequences of Cre-expression such as lack of fidelity, toxicity or off-target effects need to be taken into consideration. We report on a transgenic murine model of FLT3-ITD induced disease, where Cre-recombinase expression alone, and in the absence of a conditional allele, gives rise to an aggressive leukemia phenotype. Here, expression of various Cre-recombinases leads to polyclonal expansion of FLT3ITD/ITD progenitor cells, induction of a differentiation block and activation of Myc-dependent gene expression programs. Our report is intended to alert the scientific community of potential risks associated with using this specific mouse model and of unexpected effects of Cre-expression when investigating cooperative oncogenic mutations in murine models of cancer. Overall design: Scl-CreERT:Flt3ITD/ITD and control mice were treated 2 weeks with tamoxifen to induce Cre expression. After 2 weeks post treatment bone marrow was extracted and cells FACS sorted for haematopoietic stem and progenitor cells (LSKs; Lineage-Sca1+Kit+).

动物模型是重现急性髓系白血病 (Acute Myeloid Leukemia，AML) 基因定义亚型的宝贵工具，同时可用于评估疾病进展过程中复合突变与克隆进化的潜在影响。对于FLT3-ITD (FMS-like tyrosine kinase 3 internal tandem duplication) 阳性AML这类难治性白血病而言，这一点尤为关键。
尽管由Cre重组酶 (Cre-recombinase) 介导的条件性基因靶向技术是一项革新了生物医学研究的强大技术，但仍需考虑Cre表达所带来的保真度缺失、毒性或脱靶效应等后果。
本研究报道了一种由FLT3-ITD诱导发病的转基因小鼠模型：该模型中仅表达Cre重组酶且不存在条件性等位基因时，即可引发侵袭性白血病表型。在此模型中，不同Cre重组酶的表达可导致FLT3ITD/ITD祖细胞发生多克隆扩增、诱导分化阻滞，并激活依赖于MYC的基因表达程序。
本研究旨在提醒科学界：使用该特定小鼠模型存在潜在风险，且在癌症小鼠模型中研究协同致癌突变时，Cre表达可能产生未预期的效应。
整体实验设计：将Scl-CreERT:Flt3ITD/ITD小鼠与对照小鼠经他莫昔芬处理2周以诱导Cre表达。处理后2周，提取骨髓细胞，并通过荧光激活细胞分选 (Fluorescence-Activated Cell Sorting，FACS) 分选出造血干祖细胞 (LSKs；Lineage-Sca1+Kit+)。