Role of PGDH in leukemia pathogenesis

描述(申请人提供)：本申请中提出的研究的总体目标是调查维持白血病干细胞的分子途径，最终目标是确定新的癌症生物标记物和治疗靶点。建议的研究建立在我们最近的发现基础上，PGDH(NAD+依赖的15-羟基前列腺素脱氢酶)是参与前列腺素代谢失活的关键酶，与急性白血病的一个主要亚群的发病有关。它在白血病干细胞中高度表达，并在调节白血病干细胞自我更新的MLL/HOX途径中发挥重要的中介作用。与早先提出的保护作用不同的是，PGDH的作用是非常意想不到的，因为它以前并没有与癌症病因有关。更令人意想不到的是，我们观察到PGDH在白血病发病中的作用不依赖于它的酶活性，从而推断PGDH具有以前未知的非规范和新的生化功能。我们假设PGDH定性地调节自我更新以诱导异常的干细胞和/或祖细胞扩张，这一假设将在三个具体目标中得到解决。在特定的目标#1中，我们将确定前列腺素脱氢酶在白血病发病机制中的非典型作用机制。我们将在小鼠模型系统中使用功能获得遗传学方法，进行结构/功能研究，以确定PGDH的白血病特异性功能结构域。这将指导后续的生化研究，以确定与PGDH致癌贡献所需的必要结构域具体相关的蛋白质。具体目标#2的研究将利用急性白血病的小鼠模型以及人类白血病细胞系和细胞的组合来确定PGDH在白血病干细胞中所维持的分子通路。将使用高通量表达谱技术，结合高端生物信息学来表征受PGDH影响的分子通路，以确定其在人类白血病亚型中的作用。在具体目标#3中，我们将使用遗传学方法确定PGDH在正常造血中的作用，特别强调在PGDH条件性基因敲除小鼠中造血干细胞的维持和自我更新。与正常干细胞相比，更多地了解PGDH在癌症中的非规范功能将提供一个独特的生物标志物，并通过选择性靶向白血病干细胞而不使用造血干细胞来促进实现更有效的治疗。

DESCRIPTION (provided by applicant): The overall objectives of the studies proposed in this application are to investigate the molecular pathways that sustain leukemia stem cells with the ultimate goal of defining novel cancer biomarkers and therapeutic targets. The proposed studies build on our recent discoveries that PGDH (NAD+-dependent 15-hydroxyprostaglandin dehydrogenase), a key enzyme involved in metabolic inactivation of prostaglandins, is implicated in the pathogenesis of a major subset of acute leukemia. It is highly expressed in leukemia stem cells, and serves as a crucial mediator in the MLL/HOX pathway that regulates leukemia stem cell self-renewal. The implicated role of PGDH is highly unexpected, as it has not previously been associated with contributing to cancer causation, which contrasts with earlier proposed protective roles. Even more unexpected, is our observation that the contributions of PGDH to leukemia pathogenesis are independent of its enzymatic activity, thus inferring that PGDH has a previously unknown non-canonical and novel biochemical function. We hypothesize that PGDH qualitatively regulates self-renewal to induce aberrant stem cell and/or progenitor expansion, a hypothesis that will be addressed in three specific aims. In Specific Aim #1, we will determine the mechanism for the non-canonical role of PGDH in leukemia pathogenesis. Using gain-of-function genetic approaches in mouse model systems, we will perform structure/function studies to identify leukemia-specific functional domains of PGDH. This will direct subsequent biochemical studies to identify proteins that specifically associate with essential domains required for PGDH oncogenic contributions. Studies in Specific Aim #2 will define the molecular pathways sustained by PGDH in leukemia stem cells using a combination of mouse models of acute leukemia as well as human leukemia cell lines and cells. The molecular pathways affected by PGDH will be characterized using high throughput expression profiling techniques, in conjunction with high-end bioinformatics to establish its role in human leukemia subtypes. In Specific Aim #3 we will define the role of PGDH in normal hematopoiesis using a genetic approach with a particular emphasis on hematopoietic stem cell maintenance and self-renewal in PGDH conditional knockout mice. A greater understanding of the non-canonical functions of PGDH in cancer versus normal stem cells will provide a unique biomarker and facilitate efforts to achieve more efficacious therapies by selectively targeting leukemia stem cells while sparing hematopoietic stem cells.