Neoantigen-specific T cell responses for Fibrolamellar Hepatocellular Carcinoma

项目摘要 纤维板层状肝细胞癌(FLC)是一种罕见且通常致命的肝癌，主要影响 无肝硬变的儿童和青壮年。目前还没有批准的系统性治疗FLC的方法，通常是 对为其他形式的肝癌开发的治疗方法无效。一份相互嵌合的文字记录 DNAJB1和PRKACA被确定为FLC中的标志性基因组事件，并导致结构性激活 但用传统的小分子抑制剂对FLC的PKAc有药理抑制作用。 由于靶标毒性，这是不可行的。我们小组和其他人之前的工作已经证明，新抗原 来源于基因融合，包括FLC中的DNAJB1-PRKACA融合，可以刺激强烈的T细胞反应。 此外，所有FLC患者在融合连接处共享相同的氨基酸序列，从而允许 单一的“现成”新抗原特异性疫苗将几乎普遍用于这种癌症。新抗原- 特定疫苗与包括ICIS在内的其他免疫调节剂结合使用最有效 防止T细胞耗尽。我们的总体假设是，针对DNAJB1的新抗原特异性疫苗- PRKACA嵌合体将与ICIS协同作用，在FLC中诱导特异性抗肿瘤免疫反应。我们将进行 靶向DNAJB1-PRKACA嵌合体疫苗(FLC-Vac)联合尼伏卢单抗的临床试验 和ipilimumab，用于不能切除的FLC患者。我们将进一步确定FLC-VAC是否与ICIS相结合 增加DNAJB1-PRKACA嵌合体的新表位特异性T细胞的数量 输送到肿瘤的外周血液。配对前处理和后处理的多重免疫组织化学(IHC) 治疗活检将进一步确定免疫反应和免疫治疗抵抗的机制 FLC。我们将使用这些样本来鉴定FLC融合蛋白在小鼠体内的特异性T细胞受体(TCR) 患者的人类白细胞抗原的背景。使用来自我们试验的TCR和来自未治疗的内源性反应 标本，我们将使用人源化的小鼠原位模型来确定处理的相对效率 以及在不同的MHC环境中提供DNAJB1-PRKACA融合的特定表位。这些型号将 涉及我们将用原代细胞治疗的肿瘤系内的FLC融合的内源性呈现 与我们识别的TCR进行转换，使我们能够比较针对特定TCR的靶向效率 相应的融合表位。这项工作可能会为FLC提供一种新的治疗模式，FLC是一种 目前尚无标准或有效的系统治疗方法，这对防治复发具有重要意义。 在其他免疫抵抗型肿瘤中，“无法用药”的驱动基因。筛选最佳多肽--人类白细胞抗原-TCR 靶向DNAJB1-PRKACA融合的组合也将为下一代奠定基础 FLC的临床试验，包括对DNAJB1-PRKACA融合具有特异性的过继细胞疗法。

Project Abstract Fibrolamellar hepatocellular carcinoma (FLC) is a rare and often lethal form of liver cancer that primarily affects children and young adults without cirrhosis. There are no approved systemic therapies for FLC, and it is usually refractory to treatment approaches developed for other forms of liver cancer. A chimeric transcript between DNAJB1 and PRKACA was identified as a signature genomic event in FLC and leads to constitutive activation of PKAc, but pharmacological inhibition of PKAc for FLC with traditional small molecule inhibitors has been infeasible due to on-target toxicity. Prior work from our group and others has demonstrated that neoantigens derived from gene fusions, including the DNAJB1-PRKACA fusion in FLC, can stimulate strong T cell responses. Furthermore, all patients with FLC share an identical amino acid sequence at the fusion junction, allowing a single “off the shelf” neoantigen-specific vaccine to be utilized nearly universally for this cancer. Neoantigen- specific vaccines are most effective in combination with other immunomodulatory agents including ICIs to prevent T cell exhaustion. Our overall hypothesis is that a neoantigen-specific vaccine targeting the DNAJB1- PRKACA chimera will synergize with ICIs to elicit a specific antitumor immune response in FLC. We will conduct a clinical trial of a vaccine targeting the DNAJB1-PRKACA chimera (FLC-Vac), in combination with nivolumab and ipilimumab, in patients with unresectable FLC. We will further determine if FLC-Vac combined with ICIs increases the number of neoepitope-specific T cells with specificity for the DNAJB1-PRKACA chimera in the peripheral blood that traffic to the tumor. Multiplex immunohistochemistry (IHC) on paired pretreatment and on- treatment biopsies will further define the mechanisms of immune response and resistance to immunotherapy in FLC. We will use these samples to identify T cell receptors (TCRs) specific for the FLC fusion protein in the context of the patient's HLA. Using TCRs from our trial and from endogenous responses identified in untreated specimens, we will use humanized mouse orthotopic models to determine the relative efficiency of processing and presenting specific epitopes from the DNAJB1-PRKACA fusion in diverse MHC contexts. These models will involve the endogenous presentation of the FLC fusion within tumor lines that we will treat with primary cells transduced with our identified TCRs, allowing us to compare the targeting efficiency of TCRs specific for the corresponding fusion epitopes. This work may advance a novel treatment paradigm for FLC, a tumor for which there is no standard or effective systemic therapy, and will have important implications for targeting recurrent ”undruggable” driver genes in other immune-resistant tumor types. Identifying optimal peptide-HLA-TCR combinations for targeting the DNAJB1-PRKACA fusion will also lay the groundwork for the next generation clinical trials for FLC, including adoptive cell therapies with specificity for the DNAJB1-PRKACA fusion.