Role of constitutive androstane receptor in cyclophosphamide-based chemotherapy

说明(申请人提供)：环磷酰胺(CPA)是一种烷基化前药，已被广泛用于治疗血液系统恶性肿瘤，特别是作为非霍奇金淋巴瘤和慢性淋巴细胞白血病一线方案的重要组成部分。不幸的是，尽管进行了积极的化疗，但仍有相当数量的患者由于产生耐药性和/或无法耐受的毒性而未被治愈。显然，有必要进一步优化目前的治疗方案。这项提案的总体目标是 目的是通过促进CPA通过细胞色素P42B6代谢转化为具有药理活性的4-羟基环磷酰胺(4-OH-CPA)，而不是通过细胞色素P3A4代谢转化为N-十氯乙基环磷酰胺和有毒的氯乙醛，从而提高CPA类化疗的疗效。为此，我们已经证明，激活人的结构性雄烷受体(HCAR)优先诱导肝脏CYP2B6的表达，而不是CYP3A4，并增加4-OH-CPA的形成。我们还建立了一种独特的人类原代肝细胞(HPH)-白血病共培养模型，并证明了CPA与选择性HCAR激活剂共同给予CPA可显著增强白血病细胞的凋亡，而不会增加肝脏毒性。在这一应用中，我们假设HCAR的激活可以选择性地增加全身4-OH-CPA的暴露，并增加基于CPA的淋巴瘤和白血病治疗的疗效：毒性比。这一中心假说将通过以下特定目的来验证：目的1.评估Hcar在HPH和淋巴瘤/白血病细胞中CPA的生物激活中的作用；目的2.在HPH-淋巴瘤/白血病共培养模型中评估CPA的代谢和抗癌活性；以及目的3.在Hcar转基因小鼠模型中检测Hcar激活对基于CPA的淋巴瘤/白血病治疗的影响。这一结果有望使HCAR成为一个新的治疗靶点，促进以CPA为基础的血液系统恶性肿瘤的化疗。更好地理解HCAR介导的CPA抗癌活性相关的潜在机制(S)，可能最终有助于新治疗策略的开发。

DESCRIPTION (provided by applicant): Cyclophosphamide (CPA), an alkylating prodrug, has been used extensively in the treatment of hematologic malignancies, in particular, as an important component in the front-line regimens for non-Hodgkin lymphoma and chronic lymphocytic leukemia. Unfortunately, despite aggressive chemotherapy, a significant number of patients remain uncured due to development of drug resistance and/or intolerable toxicities. The need for further optimization of the current regimens is evident. The overall goal of this proposal is to improve the therapeutic efficacy of CPA-based chemotherapy by enhancing metabolic conversion of CPA to the pharmacologically active 4-hydroxylcyclophosphamide (4-OH-CPA) via CYP2B6, but not to the N- dechloroethyl-cyclophosphamide and the toxic chloroacetaldehyde by CYP3A4. Towards this end, we have shown that activation of the human constitutive androstane receptor (hCAR) preferentially induced the expression of hepatic CYP2B6 over CYP3A4 and increased the formation of 4-OH-CPA. We have also developed a unique human primary hepatocyte (HPH)-leukemia coculture model and demonstrated that co- administration of CPA with a selective hCAR activator leads to significantly enhanced apoptosis in leukemia cells without increasing hepatotoxicity. In this application, we hypothesize that activation of hCAR can selectively enhance systemic exposure to 4-OH-CPA and increase the efficacy:toxicity ratio of CPA-based treatment for lymphoma and leukemia. This central hypothesis will be tested by the following specific aims: Aim #1. Evaluate the role of hCAR in the bioactivation of CPA in HPH and lymphoma/leukemia cells; Aim #2. Assess the metabolism and anticancer activity of CPA in the HPH-lymphoma/leukemia coculture model; and Aim #3. Examine the influence of hCAR activation on CPA-based treatment of lymphoma/leukemia in an hCAR-transgenic mouse model. The outcomes are expected to establish hCAR as a novel therapeutic target facilitating the CPA-based chemotherapy for hematopoietic malignancies. Improved understanding of the underlying mechanism(s) associated with hCAR-mediated enhancement of the anticancer activity of CPA may ultimately benefit the development of new therapeutic strategies.