Bone Marrow Microenvironmental Expression of Cytochrome P450 Enzymes

 描述(由申请人提供)：本提案描述了一项关于骨髓微环境在调节维甲酸动态平衡中的作用的研究计划，以及将首席研究员Gabriel Ghiaur博士从初级教员发展为独立内科科学家的培训计划。Dr。 吉奥尔在大卫·威廉姆斯博士的实验室读研究生时研究正常的造血，然后在辛辛那提儿童医院的何塞·坎塞拉斯博士的实验室做博士后研究员。作为约翰·霍普金斯大学理查德·琼斯博士实验室的血液学研究员，他专注于维甲酸(RA)在造血中的作用。琼斯博士是第一个将视黄醛脱氢酶确定为正常和恶性造血干细胞的标志物的研究人员，他是该领域公认的专家。在完成临床和研究奖学金后，吉奥尔博士于2013年7月加入约翰霍普金斯大学血液恶性病学部担任讲师，最近被提升为肿瘤学和医学系助理教授。这一基于实验室的终身制职位保证了吉奥尔博士80%的受保护的研究时间，这笔赠款将支持他追求以实验室为基础的恶性血液病翻译研究人员的职业目标。无论是在稳态条件下还是在疾病状态下，造血干细胞(HSC)功能的调节都是一个密集的研究领域。多种细胞内在和环境因素已被提出将生理需求和干细胞行为联系起来。将HSC与其更坚定的祖细胞进行比较的研究表明，RA是HSC功能的潜在调节因子。为此，HSC似乎被认为是分化的，如果没有受到RA代谢酶CyP26基质表达维持的RA低生态位的保护。因此，例如，炎症信号对CYP26表达的调节可以改变壁龛中的RA水平，从而调整HSC的行为，以应对血液压力。更重要的是，由于RA疗法使急性早幼粒细胞白血病的治疗发生了革命性变化，但不幸的是对其他血液系统恶性肿瘤没有影响，因此结合间质CYP保护机制可以扩大分化疗法的临床应用。更好地了解利基药物 在开发CYP抑制剂作为血液学的临床工具之前，需要了解代谢特性以及它们在血液应激和治疗过程中的变化。这项研究的主要假设是，不同造血微环境表达的P450酶在骨髓中创建无药物庇护所，调节HSC动态平衡和化疗耐药性。该建议旨在：1)确定骨髓生态位如何控制RA的生物利用度以改变HSC的行为；具体地说，哪些干细胞生态位(内皮细胞、间充质干细胞或骨内膜干细胞)依赖细胞色素P26活性来维持人的HSC，局部(生态位)控制RA水平与全身(肝脏)代谢的比较，以及血液应激期间RA代谢的变化。2)研究间质细胞色素P450在耐药中的作用，首先是与耐药RA治疗有关，然后是与一般化疗有关。研究人员假设，对局部药物代谢的深入了解将有助于设计最佳策略，绕过间质药物代谢酶构成的化学屏障，从而为全身化疗打开恶性干细胞的利基。

 DESCRIPTION (provided by applicant): This proposal describes a research plan into the role of bone marrow microenvironment in modulating retinoid homeostasis with implications for both normal as well as malignant hematopoiesis and a training program to develop the principal investigator, Dr. Gabriel Ghiaur from a junior faculty into an independent physician-scientist. Dr. Ghiaur studied normal hematopoiesis as a graduate student in the laboratory of Dr. David Williams and then as a post-doctoral fellow in the laboratory of Dr. Jose Cancelas at Cincinnati Children's Hospital. As a hematology fellow in the laboratory of Dr. Richard Jones, Johns Hopkins University, he focused on the role of retinoic acid (RA) in hematopoiesis. Dr. Jones was the first investigator to identify retinaldehyde dehydrogenase as a marker of normal and malignant hematopoietic stem cell and is a recognized expert in the field. Upon completion of his clinical and research fellowship, Dr. Ghiaur has joined the Hematological Malignancies division, at Johns Hopkins in July 2013 as an Instructor and was recently promoted to Assistant Professor of Oncology and Medicine. This laboratory based tenure track position assure Dr. Ghiaur 80% protected time for research and this grant will support his goal of pursuing a career as a laboratory based translational researcher in hematologic malignancies. Regulation of hematopoietic stem cell (HSC) function during steady state conditions as well as during disease states is an area of intense research. Multiple cell-intrinsic and environmental cues have been proposed to connect physiological needs and stem cell behavior. Studies comparing HSC with their more committed progenitor cells, revealed RA as a potential regulator of HSC function. To this end, HSCs appear posed to differentiate if not protected by a RA-low niche maintained via stromal expression of CYP26, a RA- metabolizing enzyme. Thus, modulations of CYP26 expression by inflammatory signals for instance could change RA levels in the niche and thus, adjust HSC behavior to respond to hematological stress. More so, since RA therapies have revolutionized the treatment of acute promyelocytic leukemia but unfortunately had no impact on other hematological malignancies, tempering with stromal CYP protective mechanisms could expand the clinical applications of differentiation therapies. A better understanding of niche drug metabolizing properties and how they change during hematological stress and during therapy is needed to before the develop CYP inhibitors as clinical tools in hematology. The overarching hypothesis of the proposed research is that P450 enzymes expressed by various hematopoietic microenvironments create drug-free sanctuaries in the bone marrow and modulate HSC homeostasis as well as chemotherapy resistance. This proposal aims to: 1) Determine how the bone marrow niche controls RA bioavailability to modify HSC behavior; specifically what stem cell niche (endothelial, mesenchymal or endosteal) depends on CYP26 activity to maintain human HSC, how the local (niche) control of RA levels compares to systemic (hepatic) metabolism and how RA metabolism changes during hematological stress. 2) Study the effects of stromal cytochrome P450 on drug resistance, initially as it relates to resistance RA therapy and then as it relates to chemotherapy in general. The investigators hypothesize that a sophisticated understanding of local drug metabolism will aid in designing optimal strategies to bypass the chemical barriers posed by stromal drug metabolizing enzymes and thus, opening the malignant stem cell niche to systemic chemotherapy.