STRATEGIES TO ENHANCE VIROTHERAPY FOR BREAST CANCER

描述(申请人提供)：乳腺癌是美国女性最常见的癌症。尽管最近常规治疗有所改善，但晚期乳腺癌的预后仍然非常差，仅在美国每年就导致超过4.5万人死亡。因此，开发新的治疗方式是非常重要的。这项提案中概述的研究的长期目标是开发一种有效和安全的转移性乳腺癌病毒疗法。核心假设是，溶瘤单纯疱疹病毒(HSV)的抗肿瘤活性可以通过将细胞-膜融合功能整合到病毒中而显著增强，这将在肿瘤中产生合胞体，从而直接增强病毒的破坏力，并即使在宿主的抗病毒免疫存在的情况下也促进其在肿瘤内的扩散。第二个假设是融合溶瘤单纯疱疹病毒体内杀伤肿瘤的独特机制可以诱导强大的抗肿瘤免疫反应，从而进一步促进肿瘤的清除。特定目的1旨在确定通过将两个独立的细胞-膜融合机制整合到病毒中而构建的双融合溶瘤HSV是否能够为乳腺癌的远处器官转移提供有效的长期治疗。为了实现这一目标，还将充分评估这种病毒的安全性。目的2探讨融合溶瘤单纯疱疹病毒诱导抗肿瘤免疫的能力。首先，在小鼠乳腺肿瘤模型中，将直接比较融合基因和非融合基因溶瘤HSV诱导的抗肿瘤效果和伴随的抗肿瘤免疫。然后，免疫细胞(例如，CD4+和CD8+T细胞)的抗体耗竭将被用来确定肿瘤特异性免疫反应是否直接有助于肿瘤的根除，以及哪些免疫细胞负责抗肿瘤免疫。实验还将对融合溶瘤单纯疱疹病毒增强抗肿瘤免疫的机制进行剖析。在目的3中，将检测预先存在的抗病毒免疫对融合基因和非融合基因HSV在转移性乳腺中传播和抗肿瘤效果的影响。然后，将进行实验，以确定通过脂质体形式的病毒DNA或通过细胞载体系统地传递溶瘤HSV是否可以逃避宿主的抗病毒免疫。建议的研究将为使用融合溶瘤HSV治疗转移性乳腺癌建立强有力的临床前理论基础，并将作为人类临床试验的必要基础。最后，如果在乳腺癌中取得成功，这种治疗策略可能也适用于其他实体肿瘤。

DESCRIPTION (provided by applicant): Breast cancer is the most common cancer of women in the United States. Despite recent improvements in conventional treatments, advanced breast cancer still has an extremely poor prognosis, resulting in more than 45,000 deaths each year in the US alone. The development of new therapeutic modalities is therefore of great importance. The long-term goal of the research outlined in this proposal is to develop an effective and safe virotherapy for metastatic breast cancer. The central hypothesis is that the antitumor activity of an oncolytic herpes simplex virus (HSV) can be significantly enhanced by incorporating a cell-membrane fusion function into the virus, which will produce syncytia formation in the tumor, thereby directly enhancing the destructive power of the virus and promoting its intratumor spread even in the presence of host's antiviral immunity. The second hypothesize is that the unique mechanism of tumor destruction in vivo by the fusogenic oncolytic HSV can induce strong antitumor immune responses, which can further facilitate tumor eradication. Specific Aim 1 seeks to determine if a doubly fusogenic oncolytic HSV, which was constructed by incorporating two independent cell-membrane fusion mechanisms into the virus, can provide effective and long-term therapy to distant organ metastases of breast cancer. The safety of this virus will also be fully assessed in this aim. Specific Aim 2 sets to explore the ability of tumor destruction by the fusogenic oncolytic HSV to induce antitumor immunity. First, the antitumor effect and the accompanying antitumor immunity induced by fusogenic and nonfusogenic oncolytic HSVs will be directly compared in a murine mammary tumor model. Then antibody depletion of immune cells (e.g., CD4+ and CD8+ T cells) will be used to determine if the tumor-specific immune response directly contributes to tumor eradication and which immune cells are responsible for the antitumor immunity. Experiments will also be conducted to dissect the mechanism of enhancement of antitumor immunity by fusogenic oncolytic HSVs. In Aim 3, the influences of pre-existing antiviral immunity on spread and antitumor effect of fusogenic and non-fusogenic HSVs in metastastic breast will be examined. Then experiments will be conducted to determine if systemic delivery of oncolytic HSV through liposome-formulation of viral DNA or through cell-carriers can evade host's antiviral immunity. The proposed studies will establish a strong preclinical rationale for using the fusogenic oncolytic HSV to treat metastatic breast cancer and will serve as the necessary foundation for a human clinical trial. Finally, if successful in breast cancer, this therapeutic strategy may be applicable to other solid tumors.