Using Targeted Immunotherapy to Enhance Chemotherapy of Colorectal Cancer

描述(申请人提供)：预计2005年美国将新增145,290例结直肠癌病例和超过54,290例死亡病例。大约20%的患者在最初诊断时存在转移性结肠癌，另有25%的患者最终发展为远处转移。虽然联合化疗的进展改善了预后，但化疗(5-氟尿嘧啶(5-FU)/亚叶酸钙与伊立替康或奥沙利铂)后不能切除的转移性结直肠癌患者的中位总生存期约为2年。绝大多数结直肠癌存在基因改变[P53的丢失/失活；表皮生长因子受体(EGFR)的表达/激活增加]，这些改变干扰了DNA损伤后的死亡信号，限制了化疗药物的抗肿瘤效果。我们的研究表明，化疗药物(伊立替康、奥沙利铂)可诱导自然杀伤(NK)细胞使用的刺激性受体NKG2D、D-TCR+T细胞和α-TCR+T细胞的P53非依赖性配体的表达，以用于肿瘤的免疫监视。我们发现，这些药物还与NK细胞和T细胞介导的免疫细胞毒的关键效应分子APO2配体/肿瘤坏死因子相关的凋亡诱导配体(Apo2L/TRAIL)协同诱导结肠癌细胞P53非依赖的凋亡。具体目的1旨在确定免疫系统在体内化疗药物治疗结直肠癌的抗肿瘤疗效中的作用。建议的研究将检验DNA损伤诱导的NKG2D配体上调增强肿瘤细胞对免疫系统的敏感性并有助于体内化疗药物抗肿瘤疗效的假设，以及在多周期化疗过程中自然杀伤(NK)细胞或其他免疫效应分子的累积耗尽是否削弱化疗药物的抗肿瘤效果。具体目标2将确定是否可以通过利用树突状细胞(DC)-NK细胞相互作用来激活免疫系统[合成CpG寡脱氧核苷酸(CpG ODN)或感染减毒单核细胞增生性李斯特菌(Lm)]的策略来增强化疗的有效性。我们的前提是，DC-NK细胞的串扰不仅可以利用先天免疫系统来提高化疗的疗效，还可以促进对肿瘤杀伤过程中产生的肿瘤抗原产生持久的适应性免疫反应。虽然CpG ODN或减毒的LM可以诱导抗肿瘤免疫反应，但我们的研究表明，结肠癌细胞通过EGFR诱导的干扰线粒体死亡信号的生存蛋白来增强其抵御细胞毒性免疫效应细胞攻击的能力。针对EGFR的单抗(西妥昔单抗)可以通过将系统产生的免疫反应集中到EGFR+的肿瘤细胞，并使其对免疫细胞毒敏感，从而增强CpG ODN或减毒的LM的抗肿瘤效果和肿瘤特异性。这项拟议的研究试图揭示免疫系统在决定对化疗的反应中的工具作用，并确定CpG ODN或减毒的LM与西妥昔单抗联合使用的靶向免疫疗法是否可以用于改善结直肠癌对化疗的反应。

DESCRIPTION (provided by applicant): An estimated 145,290 new cases and more than 54,290 deaths attributed to colorectal cancer are expected in the United States in the year 2005. Approximately 20% of patients present with metastatic colon cancer at initial diagnosis, and another 25% ultimately develop distant metastases. Although advances in combination chemotherapy have improved outcome, median overall survival of patients with unresectable metastatic colorectal cancer following chemotherapy (5-fluorouracil (5-FU)/leucovorin with either irinotecan or oxaliplatin) is approximately 2 years. The vast majority of colorectal cancers harbor genetic alterations [loss/inactivation of p53; increased expression/activation of the epidermal growth factor receptor (EGFR)] that interfere with death signaling in response to DNA damage and limit the antitumor efficacy of chemotherapeutic agents. Our studies indicate that chemotherapeutic agents (irinotecan, oxaliplatin) induce p53-independent expression of ligands for NKG2D, a stimulatory receptor used by natural killer (NK) cells, ?d-TCR+ T cells and a¿-TCR+ T cells for immune surveillance of tumors. We find that these agents also cooperate with Apo2 Ligand/ Tumor necrosis factor- related apoptosis-inducing ligand (Apo2L/TRAIL), a key effector of NK cell- and T cell-mediated immunologic cytotoxicity, to induce p53-independent apoptosis of colon cancer cells. Specific Aim 1 seeks to establish a role of the immune system in the in vivo antitumor efficacy of chemotherapeutic agents in the treatment of colorectal cancers. The proposed studies will test the hypothesis that DNA damage-induced upregulation of NKG2D ligands enhances the sensitivity of tumor cells to the immune system and contributes to the in vivo antitumor efficacy of chemotherapeutic agents, and examine whether the cumulative depletion of natural killer (NK) cells or other immune effectors during the course of multi-cycle chemotherapy impairs the antitumor efficacy of chemotherapeutic agents. Specific Aim 2 will determine whether the efficacy of chemotherapy can be enhanced via strategies that exploit dendritic cell (DC)-NK cell interactions to activate the immune system [synthetic CpG oligodeoxynucleotides (CpG ODN) or infection with attenuated Listeria Monocytogenes (LM)]. Our premise is that DC-NK cell crosstalk may not only harness the innate immune system to improve the efficacy of chemotherapy, but also facilitate the generation of long-lasting adaptive immune responses to tumor antigens that are generated in the process of tumor killing. Although CpG ODN or attenuated LM can elicit antitumor immune responses, our studies indicate that colon cancer cells enhance their ability to withstand an attack by cytotoxic immune effector cells via EGFR-induced survival proteins that interfere with mitochondrial death signaling. Specific Aim 3 will test the hypothesis that a monoclonal antibody targeting EGFR (cetuximab) can enhance the antitumor efficacy and tumor-specificity of CpG ODN or attenuated LM by focusing systemically generated immune responses to EGFR+ tumor cells and sensitizing them to immunologic cytotoxicity. The proposed research seeks to uncover an instrumental role of the immune system in determining responses to chemotherapy and determine whether targeted immunotherapy with either CpG ODN or attenuated LM in combination with cetuximab can be used to improve the response of colorectal cancers to chemotherapy.