Oncolytic VSV for Hepatocellular Carcinoma

描述（由申请人提供）：肝细胞癌（HCC）是世界上第三大癌症死亡原因，未经治疗的患者中位生存期仅为7.8个月。靶向肿瘤的有条件复制病毒作为一类新的肿瘤治疗溶瘤剂正在被开发。水疱性口炎病毒（VSV）是一种细胞质RNA病毒，由于其抗病毒反应较弱，在肿瘤细胞中具有固有的复制特异性。我们证明VSV在培养的大鼠和人HCC细胞中具有强大的复制和细胞病变作用，而正常大鼠和人肝细胞则是难治性的。我们构建了一种融合性rVSV载体，并表明通过肝动脉输注，rVSV能够到达并复制同基因和免疫能力强的大鼠肝脏中大的多灶性HCC病变，导致肿瘤大量破坏和生存期延长，且无肝脏病理。虽然令人鼓舞，但瘤内病毒复制仅在一天后达到峰值，并且只有一小部分治疗动物实现了长期存活。肿瘤内病毒滴度超过一天的对数下降与NK细胞、中性粒细胞和巨噬细胞在肿瘤部位的浸润和积累是一致的，并且在病毒治疗之前，抗体介导的这些炎症细胞的消耗大大增强了肿瘤溶解。我们假设，通过抑制NK细胞活性和炎症细胞趋化性的异源病毒基因的载体介导表达，VSV的溶瘤效力可以显著提高，因此瘤内病毒的复制将从宿主产生中和抗体反应所需的1天延长到数天，这将导致强大的溶瘤作用并大大延长生存期。此外，当病毒剂量超过最大耐受剂量时，一些治疗大鼠表现出神经病理症状，表现为肢体瘫痪，并且在脑和脊髓的神经元中检测到病毒。我们假设可以通过分子工程VSV基因组来抑制神经元病毒的复制和传播，从而使相关病毒mrna的翻译在异源病毒的内部核糖体进入位点的指导下进行，这些异源病毒在神经元中无功能，但在HCC细胞中有活性。该研究的成功进行可能会导致未来开发强效和神经减毒的rVSV载体，作为治疗晚期HCC和其他癌症患者的有效和安全的溶瘤药物。

DESCRIPTION (provided by applicant): Hepatocellular Carcinoma (HCC) is the third leading cause of cancer deaths in the world with a median survival time of only 7.8 months in untreated patients. Conditionally replicating viruses targeted to tumors are being developed as a novel class of oncolytic agents for cancer treatment. Vesicular Stomatitis Virus (VSV) is a cytoplasmic RNA virus with inherent specificity for replication in tumor cells due to their attenuated anti- viral responses. We demonstrated robust VSV replication and cytopathic effects in cultured rat and human HCC cells, while normal rat and human hepatocytes were refractory. We have constructed a fusogenic rVSV vector and showed that through hepatic artery infusion, it reached and replicated in large multi-focal HCC lesions in the livers of syngeneic and immune-competent rats that led to massive tumor destruction and survival prolongation, and without liver pathology. While encouraging, intratumoral virus replication peaked after only one day and long-term survival was achieved in only a minor fraction of the treated animals. The logarithmic decline in intratumoral virus titers beyond one-day was co-incidental with the infiltration and accumulation of NK cells, neutrophils and macrophages at the tumor sites, and oncolysis was substantially enhanced by antibody-mediated depletion of these inflammatory cells prior to virus treatment. We hypothesize that the oncolytic potency VSV can be significantly elevated by vector-mediated expression of genes from heterologous viruses that suppress NK cell activity and chemotaxis of inflammatory cells, so that intratumoral virus replication will be extended from one to several days needed by the host to mount a neutralizing antibody response, which will lead to robust oncolysis and substantially prolonged survival. Additionally, at virus dosages above the maximum tolerated dose some treated rats exhibited signs of neuro-pathology manifested by limb paralysis, and virus was detected in neurons in the brain and spinal cord. We hypothesize that neuronal virus replication and spread can be inhibited by molecularly engineering the VSV genome so that the translation of pertinent viral mRNAs will be under the direction of internal ribosome entry sites of heterologous viruses that are non-functional in neurons but active in HCC cells. The successful conduct of the proposed research may lead to the future development of potent and neuro-attenuated rVSV vectors as effective and safe oncolytic agents to treat patients with advanced HCC and other cancers.