Chronic stress as a survival tactic Most patients with pancreatic ductal adenocarcinoma (PDA) develop liver metastases after surgical removal of their primary tumor. These metastases are thought to potentially arise from quiescent disseminated cancer cells, likely present at the time of surgery, which evade elimination by the immune system. Pommier et al. explored how these quiescent cells survive by analyzing mouse models and tissue samples from patients with PDA. They found that disseminated cancer cells do not express a cell surface molecule that triggers killing by T cells. This phenotypic feature is linked to their inability to resolve endoplasmic reticulum stress. When this stress is resolved, the disseminated cells begin proliferating and form metastases. Science, this issue p. eaao4908 Chronic endoplasmic reticulum stress allows disseminated cancer cells that form metastases to evade immune control. INTRODUCTION Pancreatic ductal adenocarcinoma (PDA) is the fourth most common cause of death from cancer worldwide and has a 5-year survival rate of 6%. Patients who have had their primary PDA surgically resected often develop metastatic disease, despite intra-operative examination of the liver confirming the absence of macrometastatic lesions. These observations lead to the conclusion that latent metastases, detectable only microscopically, were present in these patients and were responsible for the postoperative development of metastatic disease. RATIONALE Latent metastases with the potential for outgrowth had been considered to be lesions in which cancer cell proliferation is balanced by immune-mediated cancer cell death, but a more recent explanation invokes quiescent, single disseminated cancer cells (DCCs). Single, nonreplicating DCCs have been observed in several cancer types, but whether quiescence is enforced by the microenvironment or is cancer cell–autonomous is not known. Immunity, both innate and adaptive, also is likely to have a role in the selection and/or maintenance of latent DCCs. This has long been suspected on the basis of the clinical observation of donor-derived cancer in immune-suppressed recipients of allografts. However, there is an unexplained paradox of immunity preventing the outgrowth of latent metastases but not eliminating them. RESULTS We studied the metastatic process in the context of an ongoing adaptive immune response because of the occurrence of cancer cell–specific immunity in human and mouse PDA. Livers from patients and mice with PDA contained single DCCs with an unusual phenotype of being negative for cytokeratin 19–negative (CK19) and major histocompatibility complex class I (MHCI). The absence of the expression of MHCI in DCCs and the occurrence of cancer-specific CD8+ T cells in the genetically engineered mouse model of PDA, and possibly in patients with PDA, suggested that DCCs may be selected by an anticancer immune response during the metastatic process. To investigate this hypothesis, we created a mouse model that would allow us to determine how DCCs develop, their relationship to metastatic latency, and the role of immunity. Intraportal injection of immunogenic PDA cells into preimmunized mice seeded livers only with single, nonreplicating DCCs lacking MHCI and CK19, whereas naïve recipients of PDA cells had macrometastases. We found that a subpopulation of PDA cells with the phenotype of DCCs was present in vitro and that those cells are the precursors of DCCs in vivo. We found that T cells select DCCs by eliminating MHCI+ proliferating cancer cells. To identify the cell-autonomous “switch” regulating the developmental state of the metastases, we preformed single-cell RNA sequencing of PDA cells with the DCC phenotype. This transcriptomic analysis demonstrated an endoplasmic reticulum (ER) stress response. Moreover, DCCs showed a lack of activation of the IRE1α (inositol-requiring enzyme 1α) pathway of the unfolded protein response, whereas the PERK (protein kinase RNA-like ER kinase) pathway was activated, suggesting that DCCs cannot resolve ER stress. Relieving ER stress pharmacologically with a chemical chaperone or genetically by overexpression of spliced XBP1, in combination with T cell depletion, stimulated outgrowth of macrometastatic lesions containing PDA cells expressing MHCI and CK19. CONCLUSION We find that a PDA-specific adaptive immune response selects DCCs, in which the ER stress response accounts for both quiescence and resistance to immune elimination. Accordingly, outgrowth of DCCs to macrometastases requires not only relief from the cancer cell–autonomous ER stress response, but also suppression of systemic immunity. Thus, the ER stress response is a cell-autonomous reaction that enables DCCs to escape immunity and establish latent metastases. Unresolved ER stress allows disseminated cancer cells to escape the T cell response. Quiescent cancer cells that exhibit unresolved ER stress lack expression of MHCI. They avoid killing by T cells and become latent disseminated cancer cells (DCCs). Resolution of ER stress allows DCCs to regain proliferative capacities and grow as overt metastases, only if the T cell response is disrupted, because they also regain the expression of MHCI. Ecad, E-cadherin. The majority of patients with pancreatic ductal adenocarcinoma (PDA) develop metastatic disease after resection of their primary tumor. We found that livers from patients and mice with PDA harbor single disseminated cancer cells (DCCs) lacking expression of cytokeratin 19 (CK19) and major histocompatibility complex class I (MHCI). We created a mouse model to determine how these DCCs develop. Intraportal injection of immunogenic PDA cells into preimmunized mice seeded livers only with single, nonreplicating DCCs that were CK19– and MHCI–. The DCCs exhibited an endoplasmic reticulum (ER) stress response but paradoxically lacked both inositol-requiring enzyme 1α activation and expression of the spliced form of transcription factor XBP1 (XBP1s). Inducible expression of XBP1s in DCCs, in combination with T cell depletion, stimulated the outgrowth of macrometastatic lesions that expressed CK19 and MHCI. Thus, unresolved ER stress enables DCCs to escape immunity and establish latent metastases.

中文翻译：

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未解决的内质网应激导致免疫抵抗、潜在的胰腺癌转移

慢性压力作为生存策略 大多数胰腺导管腺癌 (PDA) 患者在手术切除原发肿瘤后会发生肝转移。这些转移被认为可能是由静止的播散性癌细胞引起的，很可能出现在手术时，这些癌细胞逃避了免疫系统的清除。波米尔等人。通过分析 PDA 患者的小鼠模型和组织样本，探索了这些静止细胞如何存活。他们发现播散的癌细胞不表达触发 T 细胞杀伤的细胞表面分子。这种表型特征与其无法解决内质网应激有关。当这种压力得到解决时，播散的细胞开始增殖并形成转移。科学，这个问题 p。eaao4908 慢性内质网应激允许形成转移的播散癌细胞逃避免疫控制。引言 胰腺导管腺癌 (PDA) 是全球第四大癌症死亡原因，5 年生存率为 6%。手术切除原发性 PDA 的患者通常会发生转移性疾病，尽管术中肝脏检查证实没有大转移灶。这些观察得出的结论是，这些患者中存在仅在显微镜下可检测到的潜在转移，并且是转移性疾病的术后发展的原因。基本原理 具有生长潜力的潜在转移被认为是癌细胞增殖被免疫介导的癌细胞死亡平衡的病变，但最近的解释是静止的、单播散的癌细胞 (DCC)。已经在几种癌症类型中观察到了单一的、非复制的 DCC，但静止是由微环境强制执行还是癌细胞自主的尚不清楚。先天性和适应性免疫也可能在潜在 DCC 的选择和/或维持中发挥作用。根据对免疫抑制的同种异体移植受者中供体来源癌症的临床观察，人们一直怀疑这一点。然而，存在一个无法解释的免疫悖论，即免疫会阻止潜在转移的生长，但不能消除它们。结果 我们在持续的适应性免疫反应背景下研究了转移过程，因为人和小鼠 PDA 中癌细胞特异性免疫的发生。来自 PDA 患者和小鼠的肝脏含有单个 DCC，具有不寻常的表型，即细胞角蛋白 19 阴性（CK19）和主要组织相容性复合体 I 类（MHCI）呈阴性。DCCs 中 MHCI 的表达缺失和 PDA 基因工程小鼠模型中以及可能在 PDA 患者中出现癌症特异性 CD8+ T 细胞，表明 DCCs 可能在转移过程中被抗癌免疫反应选择. 为了研究这一假设，我们创建了一个小鼠模型，可以让我们确定 DCC 如何发展、它们与转移潜伏期的关系以及免疫的作用。将免疫原性 PDA 细胞门静脉内注射到预先免疫的小鼠中，仅用缺乏 MHCI 和 CK19 的单个非复制 DCC 接种肝脏，而 PDA 细胞的幼稚受体具有大转移。我们发现体外存在具有 DCC 表型的 PDA 细胞亚群，并且这些细胞是体内 DCC 的前体。我们发现 T 细胞通过消除 MHCI+ 增殖的癌细胞来选择 DCC。为了确定调节转移灶发育状态的细胞自主“开关”，我们对具有 DCC 表型的 PDA 细胞进行了单细胞 RNA 测序。这种转录组学分析证明了内质网 (ER) 应激反应。此外，DCC 显示未折叠蛋白反应的 IRE1α（需要肌醇的酶 1α）途径缺乏激活，而 PERK（蛋白激酶 RNA 样 ER 激酶）途径被激活，表明 DCC 不能解决内质网应激。用化学伴侣或通过过度表达剪接的 XBP1 来缓解内质网应激，结合 T 细胞耗竭，刺激含有表达 MHCI 和 CK19 的 PDA 细胞的大转移性病变的生长。结论 我们发现 PDA 特异性适应性免疫反应选择 DCC，其中 ER 应激反应解释了静止和对免疫消除的抵抗。因此，DCC 向大转移瘤的生长不仅需要缓解癌细胞自主内质网应激反应，还需要抑制全身免疫。因此，内质网应激反应是一种细胞自主反应，使 DCC 能够逃避免疫并建立潜伏转移。未解决的内质网应激允许播散的癌细胞逃避 T 细胞反应。表现出未解决的内质网应激的静止癌细胞缺乏 MHCI 的表达。它们避免被 T 细胞杀死并成为潜伏的播散性癌细胞 (DCC)。只有当 T 细胞反应被破坏时，内质网应激的解决才能使 DCC 重新获得增殖能力并作为明显的转移瘤生长，因为它们也重新获得了 MHCI 的表达。Ecad，E-钙粘蛋白。大多数胰腺导管腺癌 (PDA) 患者在切除原发肿瘤后发展为转移性疾病。我们发现 PDA 患者和小鼠的肝脏含有缺乏细胞角蛋白 19 (CK19) 和主要组织相容性复合体 I 类 (MHCI) 表达的单一播散性癌细胞 (DCC)。我们创建了一个小鼠模型来确定这些 DCC 如何发展。将免疫原性 PDA 细胞门静脉内注射到预先免疫的小鼠中，仅用 CK19 和 MHCI 的单个非复制 DCC 接种肝脏。DCCs 表现出内质网 (ER) 应激反应，但矛盾的是缺乏需要肌醇的酶 1α 激活和转录因子 XBP1 (XBP1s) 剪接形式的表达。XBP1s 在 DCC 中的诱导表达，结合 T 细胞耗竭，刺激了表达 CK19 和 MHCI 的大转移性病变的生长。因此，未解决的 ER 应激使 DCC 能够逃避免疫并建立潜伏转移。