Sten Cell Gene Therapy of Breast Cancer

描述（由申请人提供）：尽管在IV期乳腺癌患者中发现了肿瘤特异性免疫细胞，但它们不能控制肿瘤生长。这部分是由于肿瘤间质紧密地包裹着肿瘤巢。肿瘤基质至少在两个关键方面有助于乳腺癌的免疫逃避；通过制造物理屏障，防止肿瘤浸润性免疫细胞和恶性细胞之间的直接接触，并通过产生免疫抑制细胞因子，直接阻断免疫细胞的激活和/或吸引/激活免疫抑制细胞，如调节性t细胞。在这个提议中，我们将测试一种新的干细胞基因治疗方法，该方法针对肿瘤基质细胞，目的是使现有的免疫细胞能够控制肿瘤的生长。特定的肿瘤微环境以及肿瘤细胞产生的细胞因子/生长因子触发肿瘤浸润的造血肿瘤细胞分化为一种独特类型的巨噬细胞（即肿瘤相关巨噬细胞-“tam”），其基因表达特征与组织巨噬细胞和骨髓细胞不同。tam是常见的基质细胞类型，tam的数量与乳腺癌恶性肿瘤直接相关。我们的主要假设是：1)骨髓来源的TAM祖细胞可用于向肿瘤基质传递治疗性转基因；2)TAM独特的mRNA和microRNA表达谱可用于构建TAM特异性转基因表达系统；3)药物控制、转基因介导的基质细胞杀伤和/或基质蛋白降解能够长期控制癌症。我们提供了一系列初步数据来支持我们战略的可行性。我们将在涉及大鼠新转基因小鼠（new -tg）和同基因乳腺癌细胞（MMC）的乳腺癌小鼠模型中验证我们的假设。关键发现将在涉及4T1细胞和BALB/c小鼠的第二种乳腺癌模型中得到验证。公共卫生相关性：在肿瘤细胞中，肿瘤相关巨噬细胞（tumor-associated macrophages, tam）是最常见的细胞类型，其数量与乳腺癌恶性肿瘤直接相关。tam是一种巨噬细胞群，其表型不同于其他组织巨噬细胞和骨髓细胞。我们的中心假设是，骨髓来源的TAM祖细胞可用于向肿瘤基质传递治疗性转基因。具体来说，在乳腺癌小鼠模型中，我们计划对离体骨髓干细胞进行基因修饰，并将其移植到条件受体中，在那里它们植入并提供TAM祖细胞的连续来源，从而实现对癌症的长期控制。在这个建议中，我们将集中在转基因消除障碍，自然存在的抗肿瘤免疫细胞，由肿瘤基质产生。

DESCRIPTION (provided by applicant): Although tumor-specific immune cells are found in stage IV breast cancer patients, they are not able to control tumor growth. This is in part due to tumor stroma that tightly surrounds tumor nests. Tumor stroma contributes to immune evasion of breast cancer in at least two critical ways; by creating a physical barrier that prevents direct contact between tumor infiltrating immune cells and malignant cells, and by producing immunosuppressive cytokines that directly block activation of immune cells and/or attract/activate immuno-suppressive cells such as regulatory T-cells. In this proposal, we will test a new stem cell gene therapy approach that targets tumor stroma cells with the goal to enable existing immune cells to control tumor growth. The specific tumor microenvironment as well as cytokines/growth factors produced by tumor cells trigger differentiation of tumor-infiltrating hematopoietic tumor cells into a unique type of macrophages (so called tumor-associated macrophages -"TAMs"), with a gene expression signature that is distinct from that of tissue macrophages and myeloid cells. TAMs are the prevalent stroma cell type and the number of TAMs directly correlates with breast cancer malignancy. Our central hypotheses are that i) bone marrow derived TAM progenitors can be used to deliver therapeutic transgenes to the tumor stroma, ii) the unique mRNA and microRNA expression profile of TAMs can be used to construct TAM-specific transgene expression systems, and iii) that drug controlled, transgene mediated killing of stroma cells and/or degradation of stroma protein enable long-term control of cancer. We provide a series of preliminary data that support the feasibility of our strategy. We will test our hypotheses in a mouse model of breast cancer involving rat neu-transgenic mice (neu-tg) and syngeneic mammary carcinoma cells (MMC). Key findings will be validated in a second breast cancer model that involves 4T1 cells and BALB/c mice. PUBLIC HEALTH RELEVANCE: Among the tumor stoma cells, tumor-associated macrophages (TAMs) are the prevalent cell type and the number of TAMs directly correlates with breast cancer malignancy. TAMs are a macrophage population that is phenotypically different from other tissue macrophages and bone marrow cells. Our central hypothesis is that bone marrow derived TAM progenitors can be used to deliver therapeutic transgenes to the tumor stroma. Specifically, in a mouse model of breast cancer, we plan to genetically modify, ex vivo, bone marrow stem cells and transplant them into conditioned recipients where they engraft and provide a continuous source of TAM progenitor cells, thereby enabling long-term control of cancer. In this proposal we will focus on transgenes that eliminate obstacles to naturally existing anti-tumor immune cells, created by tumor stroma.