DIRECT INTRATUMORAL ADMINISTRATION OF DENDRITIC CELLS

树突状细胞（DC）增加的外观在人实体瘤肿块原位已间接与较好的预后相关。未成熟DC可以有效地从凋亡细胞体中获取抗原，并诱导MHC i类限制性抗原特异性细胞毒性T淋巴细胞。这一发现进一步支持了DC可能在体内引发免疫反应的“交叉启动”事件中起主导作用的概念。我们之前的研究表明，早期培养的DC在体外摄取高分子量葡聚糖颗粒和整个肿瘤裂解物方面非常活跃。由于这些发现，可以想象DC可能为触发肿瘤内的免疫反应提供了一种有效的手段，特别是在那些含有大量凋亡细胞体基线水平的肿块中。事实上，我们已经发现直接瘤内注射“非脉冲”（即非肿瘤抗原负载或脉冲）DC可以介导小鼠乳腺肿瘤结节的消退。这种抗肿瘤作用似乎与局部给药前肿瘤块内测量的基线细胞凋亡水平直接相关。重要的是，远离dc注射肿瘤结节的肿瘤结节也发生了消退。在这种小鼠乳腺肿瘤模型中，IT注射DC引起的免疫治疗效果严重依赖于局部和全身宿主源性T细胞（CD8+）免疫应答的激活。推动RO1应用的假设是，在体内诱导肿瘤细胞凋亡的方法将增强DC的治疗效果和免疫刺激能力。我们建议开发新的实验和临床策略来治疗乳腺癌，利用有效的抗原呈递DC与体内选择性诱导肿瘤凋亡的药物联合使用。我们的基本原理是基于我们在小鼠和人类肿瘤系统中开发的实验数据和方法。我们建议的具体目标是：1。实验研究DC单独或联合肿瘤细胞凋亡诱导剂对相关小鼠乳腺肿瘤模型（MT-901）的作用；2. 在II期临床试验中研究晚期乳腺癌患者直接给予DC的临床应用。我们的转化研究工作的总体目标是开发一种新的、创新的策略来治疗晚期乳腺癌，该策略将肿瘤凋亡诱导剂与DC联合使用。

Increased appearance of dendritic cells (DC) within human solid tumor masses in situ has been associated indirectly with better prognosis. Immature DC can efficiently acquire antigen from apoptotic cell bodies and induce MHC class I-restricted, antigen- specific cytotoxic T lymphocytes. This finding adds additional support to the concept that DC may play the predominant role in "cross-priming" events for the elicitation of an immune response in vivo. Our previous studies demonstrated that DC in early culture are highly active at uptaking high molecular weight dextran particles as well as whole tumor lysates in vitro. Because of these findings, it is conceivable that DC may offer an efficient means for triggering immune responses within tumors, particularly in those masses containing a significant baseline level of apoptotic cell bodies. Indeed, we have found that direct intratumoral (IT) injections of "unpulsed" (i.e. not tumor antigen-loaded or pulsed) DC can mediate the regression of established breast tumor nodules in mice. This antitumor effect appears to be directly correlated with the level of baseline apoptosis measured within the tumor mass before the local delivery of DC. Of importance, tumor nodules at distant sites from the DC-injected tumor nodule also underwent regression. The immunotherapeutic effect elicited by IT injections of DC in this murine breast tumor model is critically dependent upon activation of a host-derived T cell (CD8+) immune response, both locally and systemically. The hypothesis driving this RO1 application is that approaches that elicit enhanced apoptosis of tumors in vivo will augment both the therapeutic efficacy and immune stimulatory capacity of DC. We propose to develop new experimental and clinical strategies for the treatment of breast cancer that utilize potent antigen presenting DC combined with agents that can selectively elicit tumor apoptosis in vivo. Our rationale is based on experimental data and methodologies that we have developed in both murine and human tumor systems. The Specific Aims of our proposal are to: 1. Investigate experimentally the direct IT administration of DC alone and combined with tumor cell apoptosis-inducing agents in a relevant murine breast (MT-901) tumor model; 2. Investigate clinically in phase II trials the direct IT administration of DC in patients with advanced breast cancer. The overall goal of our translational research effort will be to develop a new, innovative strategy for the treatment of advanced breast cancer that employs tumor apoptosis-inducing agents combined with DC.