Combination gene therapy for metastatic colon cancer

描述（由申请人提供）：目前转移性结肠癌的治疗选择有限。我们的临床前研究表明，免疫调节基因治疗可能是治疗晚期转移性结直肠癌的有效方法。使用原位小鼠模型预先建立的肝结肠癌，我们已经表明，肿瘤内注射腺病毒载体表达鼠白细胞介素-12（Adv/mIL-12）和4-1BB，一种共刺激分子通常发现在活化的树突状细胞和T细胞，可以诱导树突状细胞和CD 8 + T细胞的活化和增殖。这导致肿瘤消退和治疗小鼠的存活期延长。然而，这种治疗效果因肿瘤负荷大（>8x8- 10 x10 mm 2）而显着受损。骨髓抑制细胞（MSC）和调节性T细胞（Treg）的显着积累被发现在动物携带大肿瘤。缺乏适当的抗原呈递和Treg介导的免疫抑制是肿瘤细胞逃避免疫系统的两种主要手段，并且是癌症免疫治疗的主要障碍。我们发现，当与IL-12 +抗4- 1BB组合疗法联合使用时，CD 40接合大大提高了携带大肿瘤的小鼠的长期存活率。此外，激动性抗CD 40抗体阻止MSC介导的Treg诱导。我们推测CD 40激活或Ig-CD 40配体融合蛋白激活可通过多种机制增强抗肿瘤反应：1）CD 40连接可通过CD 40信号传导抑制MSC上Treg的诱导; 2）CD 40活化可诱导MSC向树突状细胞分化，并下调抑制性受体PIR-B（配对Ig样受体B）和gp 49 B，其在MSC和未成熟DC上高度表达。本研究的主要目的是探讨CD 40介导的MSC功能调节和免疫抑制逆转的机制：1）研究抗CD 40抗体阻断MSC诱导的Treg形成的机制; 2）研究负受体信号作为对协同IL-12和4-羟色胺的无效抗肿瘤应答背后的潜在机制。3）确定阻断负抑制性受体和通过共刺激分子逆转免疫抑制对大肿瘤携带宿主中免疫活化后有效抗肿瘤应答的持续性的治疗效果。这些研究的完成不仅将为肿瘤介导的抑制和耐受机制提供新的见解，还将促进我们的免疫增强疗法的有效临床转化。

DESCRIPTION (provided by applicant): The current treatment options for metastatic colon carcinoma are limited. Our preclinical research indicates that immune-modulatory gene therapy may be effective for the treatment of advanced metastatic colorectal cancer. Using an orthotopic murine model for pre-established hepatic colon carcinoma, we have shown that intratumoral injection of an adenoviral vector expressing murine interleukin-12 (Adv/mIL-12) and 4-1BB, a co-stimulatory molecule normally found on activated dendritic and T cells, can induce dendritic cell and CD8+ T cell activation and proliferation. This leads to tumor regression and prolonged survival of treated mice. However, this therapeutic effect is significantly compromised by large tumor burdens (>8x8-10x10mm2). Significant accumulation of myeloid suppressor cells (MSC) and T regulatory cells (Treg) were found in animals bearing large tumors. The lack of proper antigen presentation and Treg mediated immune suppression are two of the main means by which tumor cells evade the immune system and present the major obstacles for cancer immune therapy. We found that CD 40 engagement greatly improved the long-term survival rate of mice bearing large tumors when used in conjunction with IL-12 + anti-4-lBB combination therapy. Furthermore, agonistic anti-CD40 antibody prevented MSC-mediated Treg induction. We hypothesize that CD40 activation by agonistic antibody or Ig-CD40 ligand fusion protein can enhance anti-tumor responses through multiple mechanisms: 1) CD40 ligation can prevent Treg induction through CD40 signaling on MSC; 2) CD40 activation can induce the differentiation of MSC into dendritic cells and downregulate the inhibitory receptors, PIR-B (paired Ig-like receptor B) and gp49b, which are highly expressed on MSC and immature DCs. Three specific aims will be pursued in order to understand the mechanisms underlying the CD40 mediated regulation of MSC function and reversion of immune suppression in the large tumor setting: 1) Study the mechanisms underlying the prevention of MSC-induced Treg development by anti-CD40 ligation; 2) Investigate the negative receptor signals as the potential mechanism behind the ineffective anti-tumor response to synergistic IL-12 and 4-1BB activation in mice with large tumor burdens; 3) Determine the therapeutic effect of blocking negative inhibitory receptors and reversing immune suppression by co-stimulatory molecules on the persistence of an effective anti-tumor response following immune activation in the large tumor bearing host. The completion of these studies will not only provide a new insight into the mechanisms of tumor mediated suppression and tolerance, but also facilitate effective clinical translation of our immune enhancing therapy.