Combining STAT3-silencing and oncolytic vaccinia virus to enhance anti-tumor therapeutic activity

 描述（由申请人提供）：该提案的主要焦点将是设计和测试表达STAT 3沉默肽如PIAS 3的溶瘤牛痘载体，以直接增强载体的溶瘤和免疫活性，增加额外的治疗机制并使肿瘤对其他疗法敏感。转录因子STAT 3（信号转导和转录激活因子3）与多种癌症类型的不良预后密切相关。活化的STAT 3促进细胞生长并防止转化细胞中的凋亡，维持肿瘤驻留白细胞中的免疫抑制状态，并与CSC分化和EMT相关。因此，靶向STAT 3具有巨大的治疗潜力。因此，STAT 3的抑制已显示触发细胞凋亡，促进抗肿瘤免疫，使肿瘤对进一步的治疗敏感，并增强对癌症疫苗的免疫原性。溶瘤病毒是活病毒癌症疗法，其复制限于恶性细胞。由于几项随机临床试验的成功，对该平台的兴趣最近又重新抬头。多种溶瘤痘苗病毒（VACV）载体已进入临床试验，包括一种表达GM-CSF作为免疫转基因的载体，该载体最近在随机化IIb期临床试验中达到了其主要终点。这突出了这些载体作为免疫疗法的潜力，并支持将STAT 3沉默与溶瘤VACV疗法相结合以产生有效的癌症治疗的假设。我们已经证明，STAT 3抑制可以增强一组肾癌和胰腺癌细胞系中病毒诱导的细胞杀伤。因此，据信， 表达人PIAS 3（活化的STAT 3的蛋白质抑制剂）的牛痘将作为一种强有力的癌症治疗剂，已知人PIAS 3阻断STAT 3与DNA结合，从而抑制其作为转录因子的功能。这得到了以下观察结果的支持：转染以表达PIAS 3功能结构域的细胞对病毒诱导的细胞死亡敏感，同时增加VACV复制。我们的初步数据还表明，抑制STAT 3可以使肿瘤相关巨噬细胞（TAM）对病毒复制敏感，因此也增强了这种组合的免疫活性。因此，我们的初步体外数据强烈表明，通过与STAT 3抑制剂组合，VACV溶瘤和免疫抑制活性均得到治疗性增强。在这里，我们将设计和测试表达PIAS 3或其他STAT 3沉默肽的溶瘤牛痘载体。这些新型治疗载体的有效性将使用人肿瘤细胞系和在小鼠肿瘤模型中进行体内检查。据信，这里生产的载体不仅提供优于当前临床载体的治疗优势，而且还可以与其他疗法协同作用，以进一步增加其肿瘤杀伤潜力。

 DESCRIPTION (provided by applicant): The main focus of this proposal will be on the design and testing of oncolytic vaccinia vectors expressing STAT3-silencing peptides such as PIAS3 in order to directly enhance the oncolytic and immunotherapeutic activity of the vectors, to add additional therapeutic mechanism and to sensitize tumors to other therapies. The transcription factor STAT3 (signal transducer and activator of transcription 3) is strongly associated with a poor prognosis in multiple cancer types. Activated STAT3 promotes cell growth and prevents apoptosis in transformed cells, maintains an immunosuppressive state in tumor-resident leukocytes and has been associated with CSC differentiation and EMT. Thus, targeting of STAT3 has tremendous therapeutic potential. As such, inhibition of STAT3 has been shown to trigger apoptosis, promote anti-tumor immunity, sensitize tumors to further therapies, and to enhance immunogenicity to cancer vaccines. Oncolytic viruses are live viral cancer therapies that have their replication restricted to malignant cells. Interest in this platform has recently sen a resurgence due to success in several randomized clinical trials. Multiple oncolytic vaccinia virus (VACV) vectors have entered clinical testing, including one expressing GM-CSF as an immunotherapeutic transgene that recently reached its primary endpoints in randomized Phase IIb clinical testing. This highlights the potential of these vectors to act as immunotherapies and supports the hypothesis for combining STAT3-silencing with oncolytic VACV therapy to create potent cancer treatments. We have demonstrated that STAT3 inhibition can enhance viral-induced cell killing in a panel of renal and pancreatic cancer cell lines. It is therefore believed that vaccinia expressing human PIAS3 (protein inhibitor of activated STAT3), which is known to block STAT3 from binding to DNA and thus inhibit its function as a transcription factor, would act as a powerful cancer therapeutic. This was supported by the observation that cells transfected to express functional domains of PIAS3 were sensitized to virus-induced cell death and simultaneously increased VACV replication. Our initial data has also indicated that inhibition of STAT3 could sensitize tumor-associated macrophages (TAMs) to viral replication, so also enhancing the immunotherapeutic activity of this combination. Our preliminary in vitro data therefore strongly suggest a therapeutic enhancement to both VACV oncolytic and immunotherapeutic activity through combination with STAT3 inhibition. Here we will design and test oncolytic vaccinia vectors expressing PIAS3 or other STAT3-silencing peptides. The effectiveness of these novel therapeutic vectors will be examined using human tumor cell lines and in vivo in mouse tumor models. It is believed that vectors produced here would not only provide therapeutic advantages over the current clinical vectors but could also synergize with other therapies to further increase their tumor-killing potential.