BASE TITLE: PREVENT CANCER PRECLINICAL DRUG DEVELOPMENT PROGRAM: PRECLINICAL EFFICACY AND ENDPOINT BIOMARKERS; TASK ORDER TITLE: EFGR AND KRAS VACCINE

肺癌作为癌症相关死亡的主要原因，在全球范围内代表着显著的临床负担，占所有癌症相关死亡的19.4%。 肺癌疾病控制的一个关键概念是预防癌前病变患者的肺癌进展，并预防既往接受过治疗的肺癌患者的肺癌复发。 最近的研究结果强烈支持在所有非小细胞肺癌（NSCLC）患者中进行EGFR突变检测，并表明针对EGFR进行预防将对控制这种疾病产生重大影响。 肺癌患者中最常见的EGFR突变（>90%）是外显子19的缺失和/或外显子21的点突变（L 858 R）。 KRAS突变是肺癌的另一个主要驱动因素，存在于大约30%的肺癌患者中。 KRAS突变也是包括胰腺癌和结肠癌在内的其他几种人类癌症的主要驱动因素，但针对KRAS的预防或治疗努力一直不成功。 由于使用小分子抑制剂抑制RAS的治疗努力已经无效，针对RAS的肿瘤特异性突变形式的肽疫苗接种已经受到显著关注。 这种免疫干预对于高风险个体特别重要，例如前/当前吸烟者和具有复发高风险的切除原发性肺癌的那些人。 研究表明，Th 1辅助细胞免疫对于免疫疗法介导的癌症根除至关重要。 MHC II限制性肽疫苗引发肿瘤抗原特异性Th 1免疫，其协调免疫抑制细胞因子环境的逆转、CD 8+细胞毒性T淋巴细胞（CTL）的募集以及通过表位扩散的应答的升级。 重要的是，虽然MHC I-表位是高度HLA-DR限制性的，但MHC II表位可以被设计为结合多个HLA-DR等位基因，因此适用于更广泛的癌症患者群体。 You等人设计了针对EGFR和KRAS的MHC II限制性多肽疫苗，并表明当在癌蛋白诱导之前接种疫苗时，这些疫苗可以显著（约80%）减少相应的肺癌转基因小鼠模型中癌蛋白驱动的肺肿瘤发生。 然而，当在癌蛋白诱导后两周给予疫苗时，观察到效力降低，表明癌基因激活后不久肿瘤微环境中存在免疫抑制机制。 高风险个体可能在肺肿瘤发生之前很久就已经具有活性致癌突变，这可能显著有助于免疫抑制微环境，从而阻碍疫苗诱导的免疫应答。 因此，测试疫苗与可以抑制免疫抑制微环境的药剂组合的功效是非常重要的。 乙酰辅酶A乙酰转移酶（ACAT）抑制剂Avasimibe（AVA）是一种抗炎药物，在治疗动脉粥样硬化的临床试验中具有良好的安全性。 最近的研究表明，AVA通过增加肿瘤特异性CD 8+细胞毒性T细胞的效应功能来促进抗肿瘤免疫应答。 活化的CD 8 + T细胞经历胆固醇代谢和合成的改变以支持快速细胞增殖。 AVA抑制胆固醇酯化，上调质膜胆固醇水平，增强T细胞受体（TCR）聚集，并促进CD 8 + T细胞中免疫突触的形成。 You等人最近的工作表明，AVA和其多肽KRAS疫苗的组合可以在肺癌的同系移植和转基因小鼠模型中引起改善的抗肿瘤功效，其中KRAS激活在接种疫苗之前很久就开始了。 基于这些数据，可以想象，当在存在亚临床疾病的情况下接种疫苗时，化学免疫预防策略（例如AVA和癌症疫苗的组合）可能是预防肺癌的合理方法。 假定该组合促进同时的CD 4+和CD 8 + T细胞应答，从而提供增强的益处以改善抗肿瘤适应性免疫应答。

Lung cancer represents a significant clinical burden worldwide as the leading cause of cancer-related mortality, accounting for 19.4% of all cancer-related deaths. A key concept in lung cancer disease control is to prevent lung cancer progression in patients bearing premalignant lesions and to prevent lung cancer recurrence in those with previously treated lung cancer. Recent findings strongly support EGFR mutation testing in all patients with non-small cell lung cancer (NSCLC) and suggest that targeting EGFR for prevention will have significant impact in controlling this disease. The most common EGFR mutations (>90%) in lung cancer patients are deletions in exon 19 and/or point mutations in exon 21 (L858R). Mutations in KRAS, another major driver of lung cancer, are present in approximately 30% of lung cancer patients. KRAS mutations are also the major driver for several other human cancers including pancreatic and colon cancer, but efforts to target KRAS preventively or therapeutically have been unsuccessful. Since therapeutic efforts to inhibit RAS using small molecule inhibitors have been ineffective, peptide vaccination against tumor-specific mutant forms of RAS have received significant attention. Such immunological interventions are particularly important for high-risk individuals, for example former/current smokers and those with resected primary lung cancer at a high risk for relapse. Studies have shown that the Th1 helper cellular immunity is critical for immunotherapy-mediated cancer eradication. MHC II-restricted peptide vaccines elicit tumor antigen-specific Th1 immunity that orchestrates the reversal of immunesuppressive cytokine environment, recruitment of CD8+ Cytotoxic T lymphocytes (CTL), and escalation of the response via epitope spreading. Importantly, while MHC I–epitopes are highly HLA-DR restricted, MHC II epitopes can be designed to bind to multiple HLA-DR alleles and are thus applicable for broader populations of cancer patients. You et al designed MHC II-restricted multi-peptide vaccines against EGFR and KRAS, and showed that these vaccines can significantly (~80%) decrease oncoprotein-driven lung tumorigenesis in corresponding transgenic murine models of lung cancer when vaccinated before oncoprotein induction. However, diminished efficacy was observed when the vaccines were given two weeks after the oncoprotein induction, suggesting the presence of immunosuppressive mechanisms in the tumor microenvironment soon after the oncogene activation. High-risk individuals may already have active oncogenic mutations long before the onset of lung tumorigenesis, which could contribute significantly to an immune suppressive microenvironment, thereby hampering the vaccine-induced immune responses. Therefore, testing efficacy of a vaccine in combination with agents that can inhibit the immune suppressive microenvironment is highly significant. The Acetyl-CoA acetyltransferase (ACAT) inhibitor, Avasimibe (AVA), is an anti-inflammatory drug that has a good safety profile in clinical trials for treating atherosclerosis. Recent studies show that AVA promotes anti-tumor immune responses by increasing the effector function of tumor specific CD8+ cytotoxic T cells. Activated CD8+ T cells undergo alterations in cholesterol metabolism and synthesis to support rapid cell proliferation. AVA inhibits cholesterol esterification, upregulates plasma membrane cholesterol levels, enhances T-cell receptor (TCR) clustering, and promotes formation of the immunological synapse in CD8+ T cells. Recent work by You et al. demonstrated that the combination of AVA and their multipeptide KRAS vaccine could elicit improved anti-tumor efficacy both in a syngraft and transgenic mouse models of lung cancer, where KRAS activation was initiated long before vaccination. Based on these data, it is conceivable that chemo-immunoprevention strategies such as combination of AVA and cancer vaccines may be a rational approach to lung cancer prevention when the vaccine is administrated in the presence of subclinical disease. The combination is postulated to promote concurrent CD4+ and CD8+ T cell responses thereby providing an enhanced benefit to improve anti-tumor adaptive immune responses.