Identification of glioma tumor-initiating cells

描述（由申请人提供）：恶性胶质瘤是最常见的原发性脑肿瘤，其特点是侵袭性生长和对当前治疗的抗性。在胶质瘤细胞类型中，多能CD133+细胞具有在免疫缺陷小鼠中引发疾病的能力（Singh等，2004）。脑肿瘤中肿瘤启动细胞类型的鉴定表明，与血液系统恶性肿瘤一样，胶质瘤的细胞异质性代表了分化状态的分层排列（Clarke et al., 2006）。根据这种模式，消除肿瘤启动细胞可能提供最大的治疗效益（Park等人，2009）。研究胶质瘤生物学中这一基本概念的主要障碍是缺乏表征胶质瘤肿瘤起始细胞表型异质性的细胞标记物。我们在原发性异种移植模型中的背景数据表明，CD133表达包括具有不同生物学特性的胶质瘤细胞的离散亚群。为了研究CD133表达所包含的细胞异质性，我们提出用恶性胶质瘤亚型分离的CD133+细胞免疫七鳃鳗，产生针对胶质瘤祖细胞的单克隆可变淋巴细胞受体（VLR）抗体。与我们的抗体结构不同的七鳃鳗抗体，将在直接原位异种移植模型中分析其识别肿瘤起始细胞及其谱系的潜力。原理验证研究表明，重组单克隆VLR抗体可用于B淋巴细胞分化不同阶段的人肿瘤细胞。我们假设，在无颌脊椎动物的VLR抗体的其他独特优势中，由于自身耐受性，哺乳动物抗体库不允许的细胞表位将被七鳃鳗抗体所利用（Herrin等，2008）。

DESCRIPTION (provided by applicant): Malignant gliomas are the most common primary brain tumors and are characterized by invasive growth and recalcitrance to current therapies. Among glioma cell types, multipotent CD133+ cells have the capacity to initiate disease in immunodeficient mice (Singh et al., 2004). The identification of a tumor-initiating cell type in brain tumors suggests that, like hematological malignancies, the cellular heterogeneity of gliomas represents a hierarchical arrangement of differentiation states (Clarke et al., 2006). According to this paradigm, elimination of tumor-initiating cells may provide the greatest therapeutic benefit (Park et al., 2009). A primary impediment to investigating this fundamental concept in glioma biology is the lack of cell markers for characterizing the phenotypic heterogeneity of glioma tumor-initiating cells. Our background data in a primary xenotransplantation model suggest that CD133 expression encompasses discrete subpopulations of glioma cells with different biological characteristics. To study the cellular heterogeneity encompassed by CD133 expression, we propose to generate monoclonal variable lymphocyte receptor (VLR) antibodies for glioma progenitor cells by immunizing lampreys with CD133+ cells isolated from malignant glioma subtypes. The lamprey antibodies, which are structurally different proteins than our antibodies, will be analyzed for their potential to identify tumor-initiating cells and their lineages in a direct orthotopic xenotransplantation model. Proof-of-principle studies demonstrate that recombinant monoclonal VLR antibodies can be made against human tumor cells representative of different stages in B lymphocyte differentiation. We postulate that among other advantages unique to the VLR antibodies of jawless vertebrates, cellular epitopes otherwise impermissible to a mammalian antibody repertoire, because of self-tolerance, will be accessible to lamprey antibodies (Herrin et al., 2008). PUBLIC HEALTH RELEVANCE: Malignant gliomas are recalcitrant to current therapies and patients with this disease currently have a poor prognosis. The identification of cell types responsible for tumor growth and recurrence may lead to the development of more effective therapies. In this proposal a novel method, the adaptive immune system of jawless vertebrates, will be used to identify glioma tumor-initiating cells and their lineages in a direct orthotopic xenotransplantation model.