STRATEGIES TO ENHANCE VIROTHERAPY FOR BREAST CANCER

描述（由申请人提供）：乳腺癌是美国女性最常见的癌症。尽管传统治疗方法最近有所改进，但晚期乳腺癌的预后仍然非常差，仅在美国，每年就有超过4.5万人死于乳腺癌。因此，发展新的治疗方式是非常重要的。这项研究的长期目标是为转移性乳腺癌开发一种有效和安全的病毒疗法。核心假设是溶瘤性单纯疱疹病毒（HSV）的抗肿瘤活性可以通过在病毒中加入细胞膜融合功能而显著增强，从而在肿瘤中产生合胞体形成，从而直接增强病毒的破坏力并促进其在宿主抗病毒免疫存在的情况下在肿瘤内扩散。第二种假设是，融合性溶瘤HSV在体内独特的肿瘤破坏机制可以诱导强烈的抗肿瘤免疫反应，从而进一步促进肿瘤的根除。特异性目的1旨在确定通过将两种独立的细胞膜融合机制整合到病毒中构建的双重融合性溶瘤性HSV是否可以为乳腺癌远处器官转移提供有效和长期的治疗。为此目的，还将充分评估该病毒的安全性。特异性目的2旨在探讨融合性溶瘤性HSV破坏肿瘤诱导抗肿瘤免疫的能力。首先，在小鼠乳腺肿瘤模型中直接比较融合性和非融合性溶瘤性单纯疱疹病毒的抗肿瘤作用和伴随的抗肿瘤免疫。然后利用免疫细胞（如CD4+和CD8+ T细胞）的抗体耗竭来确定肿瘤特异性免疫反应是否直接有助于肿瘤根除，以及哪些免疫细胞负责抗肿瘤免疫。本实验还将探讨融合性溶瘤单纯疱疹病毒增强抗肿瘤免疫的作用机制。在第3期研究中，我们将研究预先存在的抗病毒免疫对转移性乳腺中融合性和非融合性单纯疱疹病毒扩散和抗肿瘤作用的影响。然后将进行实验，以确定溶瘤性HSV通过病毒DNA脂质体制剂或通过细胞载体的全身递送是否可以逃避宿主的抗病毒免疫。拟议的研究将为使用融合性溶瘤性HSV治疗转移性乳腺癌建立强有力的临床前理论基础，并将作为人体临床试验的必要基础。最后，如果在乳腺癌中成功，这种治疗策略可能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.