DIRECT INTRATUMORAL ADMINISTRATION OF DENDRITIC CELLS

树突状细胞(DC)在原位人类实体瘤中的出现增多与更好的预后间接相关。未成熟的DC可以有效地从凋亡的细胞体中获得抗原，并诱导MHC-I类限制性的、抗原特异性的细胞毒T淋巴细胞。这一发现进一步支持了DC可能在体内激发免疫反应的“交叉启动”事件中发挥主导作用的概念。我们以前的研究表明，早期培养的DC在体外摄取高相对分子质量的葡聚糖颗粒以及整个肿瘤裂解物方面具有很高的活性。由于这些发现，可以想象，DC可能提供一种有效的手段来触发肿瘤内的免疫反应，特别是在那些含有显著基线水平的凋亡细胞体的肿块中。事实上，我们已经发现，瘤内直接注射“非脉冲”(即不负载肿瘤抗原或脉冲的)DC可以介导小鼠已建立的乳腺肿瘤结节的消退。这种抗肿瘤作用似乎与在局部注射DC之前在肿瘤内测量的基线细胞凋亡水平直接相关。重要的是，DC注射肿瘤结节远处的肿瘤结节也经历了消退。在这个小鼠乳腺肿瘤模型中，IT注射DC所产生的免疫治疗效果严重依赖于宿主来源的T细胞(CD8+)免疫反应的激活，无论是局部还是全身。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。我们建议开发新的治疗乳腺癌的实验和临床策略，利用强大的抗原提呈DC和能够选择性地在体内诱导肿瘤细胞凋亡的药物相结合。我们的理论基础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。我们建议的具体目的是：1.在相关的小鼠乳腺(MT-901)肿瘤模型中，通过实验研究DC单独和联合肿瘤细胞凋亡诱导剂的直接IT给药；2.在II期临床试验中，研究DC对晚期乳腺癌患者的直接IT给药。我们转译研究工作的总体目标将是开发一种新的、创新的策略来治疗晚期乳腺癌，该策略使用肿瘤凋亡诱导剂和DC相结合。

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.