Immunophysiological Mechanisms in the Biological Therapy of Cancer

癌症免疫治疗新方法的成功开发需要理解复杂的、相互依赖的早期先天反应元素的活动，以及随后强大的适应性免疫反应。我们正在采用几种新方法来最大限度地提高宿主产生有效抗肿瘤反应的能力。这些方法包括通过使用CD40来优化抗原提呈能力，CD40是一种TNF超家族受体，可作为树突状细胞的有效触发因子，在先天和适应性反应之间提供关键接口。当与IL-2联合使用时，激动剂CD40抗体刺激树突状细胞的效力增强，并且激动剂抗CD40与IL-2联合使用对小鼠转移性肾癌的抗肿瘤活性增强。由于CD40存在于各种造血源性细胞、内皮细胞和一些肿瘤本身，我们也进行了研究，以明确确定CD40刺激和IL-2的抗肿瘤作用是否主要由CD40+造血源性细胞介导。我们已经开发了一种方法，只有肿瘤细胞表达功能性CD40；具体来说，我们使用的模型是将仅对抗人CD40有反应的CD40+人类肿瘤植入仅表达小鼠CD40且对抗人CD40无反应的SCID小鼠。这两个模型使我们能够证明肿瘤细胞对激动剂CD40的结扎确实有反应，并且这种反应确实有助于限制肿瘤的生长。此外，靶向破坏肿瘤微环境中的其他事件可能最终揭示将免疫治疗与其他分子靶向策略相结合的新方法。为此，我们制作了与人IgG1恒定区连接的VEGF受体（vegfr）可溶性形式Flk-1和Flt-1的表达载体，并通过高效流体动力学注射将这些质粒传递给Balb/c小鼠，该策略在小鼠血清中产生高达0.1mg/ml的合适基因产物，并成功抑制了含VEGF基质中的血管生成。Balb/c小鼠肾癌的体内生长也被同样的处理阻断，特别是可溶性Flt-1。总的来说，这些类型的互补方法寻求触发几种途径，通过这些途径宿主可以识别或损害肿瘤生长，同时也针对肿瘤细胞提高自身存活或抑制抗肿瘤宿主反应的能力。

Successful development of new approaches for the immunotherapy of cancer requires an understanding of complex, interdependent activities of early innate response elements with subsequent powerful adaptive immune responses. We are taking several novel approaches to maximize the host's ability to mount an effective antitumor response. These approaches include optimizing antigen presenting capability through the use of CD40, a TNF superfamily receptor that serves as a potent trigger for dendritic cells which provide a key interface between innate and adaptive responses. The potency of dendritic cell stimulation by agonist CD40 antibodies is enhanced when used in conjunction with IL-2 and the combination of agonist anti-CD40 plus IL-2 shows enhanced antitumor activity against metastatic kidney cancer in mice. Because CD40 is present on various hematopoietic-derived cells, endothelial cells, and some tumors themselves, we have also performed studies to definitively determine if the antitumor effects of CD40 stimulation and IL-2 were primarily mediated by CD40+ hematopoietic-derived cells. We have developed an approach where only tumor cells express functional CD40; specifically we have used models where CD40+ human tumors that respond only to anti-human CD40 were implanted in SCID mice that express only mouse CD40 and do not respond to the administration of the anti-human CD40. These two models have allowed us to show that tumor cells do respond to ligation with agonist CD40 and this response does contribute to limiting tumor growth. In addition, targeted disruption of other events in the tumor microenvironment may ultimately reveal new approaches for combining immunotherapy with other molecularly targeted strategies. In this regard, we have made expression vectors encoding the soluble forms of the VEGF receptors (VEGFRs), Flk-1 and Flt-1, linked to the constant region of human IgG1, and delivered these plasmids to Balb/c mice by highly efficient hydrodynamic injection, this strategy resulted in up to 0.1mg/ml of the appropriate gene products in mouse serum and successfully inhibited angiogenesis in VEGF-containing matrigel. Growth in vivo of a Balb/c mouse renal cancer was also blocked by the same treatment, particularly with soluble Flt-1. Overall, these types of complementary approaches seek to trigger several pathways through which the host can recognize or impair tumor growth, while also targeting the ability of tumor cells to enhance their own survival or inhibit antitumor host responses.