Genotype and phenotype of chemoresistant AML

描述（由申请人提供）：AML的治疗进展来自对该疾病分子遗传学的更好理解。现在有新的建议，使用影响结果的疾病相关细胞遗传学和分子变化，既用于一般实践目的，也用于临床试验标准。然而，这些分子变化影响缓解诱导、复发和长期生存的确切机制在很大程度上是未知的，并且在每个细胞遗传学风险类别中，结果存在很大的个体差异，这些差异知之甚少。人类AML的总体结果仍然令人沮丧，大多数患者在相对较短的时间内死于耐药疾病。白血病研究的一个目标是了解驱动这些变异的潜在分子机制，以便更好地对患者进行分层，并对可能适合靶向治疗的信号通路提供额外的见解。MLL-AF 9（MA 9）是AML中常见的染色体异常，是影响染色体11 q23的易位的结果，与标准化疗的中间结果相关。我们已经证明，这种蛋白质在原代人脐带血（CB）CD 34+细胞中的表达诱导AML，中位潜伏期为10周。发现遗传畸变FLT 3-ITD（与不良结局相关）和活化N-ras（对患者结局无明显影响）均与人类原发性11 q23（+）样本相关。我们有数据显示FLT 3-ITD和N-Ras都与MA 9有效合作，并加速人类细胞中的白血病发生。我们已经建立了一个体内诱导化疗方案，使用两个主要的AML治疗，阿糖胞苷和阿霉素，并显示，我们有效地靶向白血病细胞的异种移植模型。有趣的是，MA 9 + FLT 3-ITD白血病对化疗难治，而MA 9 +N-ras白血病对化疗敏感，在某些方面模拟了临床AML患者中观察到的反应。最近的数据表明，在白血病异种移植实验中存活的细胞通常是在人类患者复发中占主导地位的克隆，这表明异种移植方法具有鉴定那些在人类疾病中构成最大风险的克隆的显著潜力。这些克隆的基因表达谱（GEP）可能是关于与耐药性相关的特定信号级联的高度信息。我们假设可以识别出一个标志，它将预测化疗反应和复发的可能性。我们将使用原代患者AML样本和我们自己的诱导型人AML异种移植模型来研究与AML治疗应答和失败相关的不同化疗敏感性，以确定确定的协同突变对化疗耐药性的基因型贡献。这个高风险/高收益的项目是基于我的实验室开发的坚实的实验方法，具有巨大的潜力，可以快速转化为临床的高影响力的发现。

DESCRIPTION (provided by applicant): Therapeutic advances in AML have come through a better understanding of the molecular genetics of the disease. New recommendations are now in place that use disease-associated cytogenetic and molecular changes that impact outcome, both for general practice purposes as well as standards for clinical trials. However, the precise mechanisms whereby these molecular changes impact on remission induction, relapse and long-term survival are unknown for the most part, and within each cytogenetic risk category, there are large individual variations in outcome that are poorly understood. Overall outcome in human AML is still dismal, with most patients succumbing to chemoresistant disease within a relatively short time. One goal in leukemia research is to understand the underlying molecular mechanisms driving these variations, to allow better stratification of patients and to give additional insight into those signaling pathways that could be amenable to targeted therapy. MLL-AF9 (MA9) is a frequent chromosomal abnormality in AML, a result of translocations affecting chromosome 11q23, and is associated with an intermediate outcome in response to standard chemotherapy. We have demonstrated that expression of this protein in primary human cord blood (CB) CD34+ cells induces AML with a median latency of 10 weeks. The genetic aberrations FLT3-ITD (associated with a poor outcome) and activated N-ras (no clear effect on outcome in patients) are both found associated with primary 11q23(+) samples in humans. We have data showing that both FLT3-ITD and N-Ras cooperate efficiently with MA9 and accelerate leukemogenesis in human cells. We have established an in vivo induction chemotherapy regimen using the two mainstays of AML treatment, cytarabine and doxorubicin, and show that we effectively target leukemia cells in the xenograft model. Interestingly, the MA9+FLT3-ITD leukemia is refractory to chemotherapy while the MA9+N-ras leukemia is chemosensitive, mimicking in some respects the response seen in AML patients in the clinic. Recent data has demonstrated that the surviving cell in leukemia xenograft experiments is frequently the clone that presides in human patient relapse, indicating that a xenograft approach has significant potential to identify those clones that pose the greatest risk in human disease. The gene expression profiles (GEP) of these clones could be highly informative with regard to the specific signaling cascades that correlate with chemoresistance. We hypothesize that a signature can be identified that will predict chemotherapeutic response and the potential for relapse. We will use both primary patient AML samples and our own inducible human AML xenograft models to study the varying chemosensitivity associated with therapy response and failure in AML, to identify the genotypic contribution of defined cooperating mutations to chemoresistance. This high-risk/high-yield project is based on solid experimental approaches developed in my lab and has great potential for high impact findings with rapid translation to the clinic.