RNA-Based Immunotherapy Targeting Antigens Unique to Brain Tumor Stem Cells

描述（由申请人提供）：NOT-OD-09-058：NIH宣布为竞争性修订申请提供恢复法案基金多形性胶质母细胞瘤（GBM）中的一个细胞亚群已被鉴定为具有独特的肿瘤再生能力。这些脑肿瘤干细胞（BTSC）已被神经干细胞标记物CD 133分离，并被广泛认为是负责对常规疗法产生抗性的细胞。特异性消除这些细胞的有效方法可以减少对密集和非特异性常规治疗的需求，并降低肿瘤复发的风险。在我们最初的提议中，我们提供了由负载有来自BTSC的扩增的总肿瘤RNA的树突状细胞（DC）组成的疫苗，作为诱导针对这些BTSC的细胞和体液抗肿瘤免疫应答的创新策略。 最近，替莫唑胺（TMZ），骨髓抑制化疗，已显示出生存与GBM患者的好处。不幸的是，预计TMZ诱导的淋巴细胞减少会减少此类疫苗诱导的有效抗肿瘤免疫应答。然而，在淋巴细胞减少期之后，例如由TMZ诱导的淋巴细胞减少期，存在宿主剩余淋巴细胞的稳态增殖，其具有降低的活化阈值。因此，在该恢复期期间遇到其同源抗原的抗肿瘤淋巴细胞（可能以疫苗的形式）可能具有竞争优势，并且在恢复的淋巴细胞群体中变得过度代表。 我们的初步数据表明，靶向肿瘤特异性抗原的肽疫苗，当在TMZ诱导的淋巴细胞减少症的恢复过程中给予时，在小鼠和人中产生显著增强的体液应答和增加的抗原特异性T细胞频率。此外，增加TMZ的剂量或用TMZ的连续循环处理产生了对疫苗接种的响应的逐渐更高的T细胞频率。这些结果强调了在从连续TMZ造血恢复期间接种疫苗作为增强抗肿瘤免疫的新策略，需要在靶向BTSC的疫苗的背景下进行研究。我们的竞争性补充建议然后研究TMZ对由负载有源自BTSC的TTRNA的DC组成的疫苗的功效的影响。 与美国复苏和再投资法案的目标相一致，该补充将加快我们在这一领域的研究克里思，并允许创造和保留就业机会。PHS 398/2590（Rev. 11/07）第1页 公共卫生相关性：恶性原发性脑肿瘤是儿童死亡的最常见原因，在成人中的死亡人数比黑色素瘤多，目前在美国提供的每质量调整生命年节省的医疗费用最高。恶性原发性脑肿瘤细胞（BTSC）的一个子集，称为脑肿瘤干细胞，具有再生肿瘤和抵抗常规治疗的独特能力。在该提案中，我们将观察在化疗诱导的骨髓抑制的背景下，BTSC优先或唯一表达的靶向抗原是否会增强免疫治疗的疗效而不诱导自身免疫。PHS 398/2590（Rev. 11/07）第1页

DESCRIPTION (provided by applicant): NOT-OD-09-058: NIH Announces the Availability of Recovery Act Funds for Competitive Revision Applications A subset of cells in glioblastoma multiforme (GBM) have been identified that enjoy a unique capacity to regenerate tumors. These brain tumor stem cells (BTSC) have been segregated by the neural stem cell marker, CD133, and are widely believed to be the cells responsible for resistance to conventional therapies. An effective means of specifically eliminating these cells may reduce the need for intensive and non-specific conventional therapy and lower the risk of tumor recurrence. In our original proposal, we offered vaccines consisting of dendritic cells (DCs) loaded with amplified total tumor RNA derived from BTSCs as an innovative strategy to induce cellular and humoral antitumor immune responses against these BTSCs. Recently, temozolomide (TMZ), a myelosuppressive chemotherapy, has shown a survival benefit in patients with GBM. Unfortunately, the lymphopenia induced by TMZ would be predicted to curtail the induction of productive antitumor immune responses by such vaccines. However, following periods of lymphopenia, such as those induced by TMZ, there is a homeostatic proliferation of the host's remaining lymphocytes, which enjoy a lowered threshold for activation. As a result, anti-tumor lymphocytes that encounter their cognate antigen during this recovery phase, perhaps in the form of a vaccine, may have a competitive advantage and become over-represented in the recovering lymphocyte population. Our preliminary data demonstrate that peptide vaccines targeting a tumor-specific antigen, when given during the recovery from TMZ-induced lymphopenia, produced dramatically enhanced humoral responses and increased antigen-specific T-cell frequencies in mice and humans. Furthermore, increasing the dose of TMZ or treating with serial cycles of TMZ generated progressively higher T-cell frequencies in response to vaccination. These results highlight vaccination during hematopoietic recovery from serial TMZ as a novel strategy for enhancing antitumor immunity that needs to be investigated in the context of vaccines targeting BTSCs. Our Competitive Supplement would propose then to investigate the effects of TMZ on the efficacy of vaccines consisting of DCs loaded with TTRNA derived from BTSCs. Consistent with the goals of the American Recovery and Reinvestment Act, this Supplement would accelerate the tempo of our research in this area and allow for job creation and retention. PHS 398/2590 (Rev. 11/07) Page 1 Continuation Format Page PUBLIC HEALTH RELEVANCE: Treatment for malignant primary brain tumors, which are the most common cause of death among children and account for more deaths in adults than melanoma, currently represents the most expensive medical therapy per quality-adjusted life-year saved currently provided in the United States. A subset of malignant primary brain tumor cells (BTSCs), called brain tumor stem cells, enjoy a unique capacity to regenerate tumors and to resist conventional therapies. In this proposal we will see if targeting antigens preferentially or uniquely expressed by BTSCs in the context of chemotherapy-induced myelosuppression will enhance the efficacy of immunotherapy without inducing autoimmunity. PHS 398/2590 (Rev. 11/07) Page 1 Continuation Format Page