DKK3 in pancreatic cancer–Elucidating the roles of a double-edged sword

胰腺导管腺癌（PDAC）是发达国家癌症相关死亡的主要原因之一，其5年生存率低于10%。尽管进行了广泛的研究，但仍然缺乏可靠的早期疾病检测和病理生理学的生物标志物。因此，对PDAC不同区室之间肿瘤内相互作用的密切分子机制的详细描述变得至关重要。DKK3 （Dickkopf-3）是参与Wnt信号传导的Dickkopf蛋白家族的成员，是一种相当独特的蛋白：在PDAC中，trp53缺失的情况下抑制DKK3会对肿瘤进展产生负面影响，并延长生存期。值得注意的是，DKK3过表达使PDAC对吉西他滨治疗敏感。我们之前确定DKK3是胰腺炎期间器官再生的一个新因素，并通过涉及一组体内模型的最新研究，描绘了DKK3与经典wnt -和刺猬信号之间的直接的，以前未知的联系。考虑到胰腺炎是胰腺癌的一个危险因素，这促使我们研究DKK3在PDAC发展中的潜在作用。我们的初步研究结果表明，DKK3在PDAC进展过程中发挥分期、室甚至转录特异性功能。有趣且具有挑战性的是，DKK3在胰腺癌发生过程中表现为“朋友”或“敌人”，这取决于其时空表达。目前的提案旨在精确表征DKK3在PDAC起始和进展过程中的相反功能，并在kras驱动的肿瘤发生的不同阶段（从早期发育不良到癌症阶段）采用尖端的体内、体外和离体实验设置。对基因工程小鼠进行复杂的研究，包括时间分辨表型和单细胞转录组测序，将有助于(i)捕获DKK3肿瘤抑制功能的微小动态；（ii）揭示随着时间的推移对各种信号级联的干扰；（iii）阐明基质和肿瘤上皮间室之间潜在的旁分泌和自分泌串扰。涉及RNA干扰和基因拯救策略的体外和离体3D共培养实验将进一步证实DKK3的隔室和转录特异性作用。同时，一个多功能的体外器官培养平台将能够长期评估早期发育不良事件和肿瘤进展。重要的是，模拟肿瘤启动事件的复杂干细胞衍生的胰管样器官不仅将巩固，而且将我们的发现转化为相关的人类模型。总之，这项研究将提供关于DKK3的关键和基本知识，DKK3是一种在癌变过程中具有双刃剑作用的蛋白质，作为一种新的真正的生物标志物和一种有希望的PDAC治疗策略而上升。

Pancreatic ductal adenocarcinoma (PDAC) is one of the leading causes of cancer-associated mortality in developed countries with a 5-year survival rate of less than 10%. Despite extensive research, there is still a lack of reliable biomarkers for early disease detection and pathophysiology. Therefore, the minute delineation of intimate molecular mechanisms involved in the intratumoral interplay between different compartments of PDAC became of paramount importance. DKK3 (Dickkopf-3), a member of the Dickkopf protein family involved in Wnt signaling, is a rather unique protein: in PDAC, suppression of DKK3 in a Trp53-deficient context negatively impacts tumor progression and prolongs survival. Notably, DKK3 overexpression sensitizes PDAC towards gemcitabine therapy. We previously identified DKK3 as a novel factor for organ regeneration during pancreatitis and, through state-of-the-art investigations involving a set of in vivo models, delineated a direct, previously unknown link between DKK3 and the canonical-Wnt- and Hedgehog-signaling. This, and given that pancreatitis renders as a risk factor for pancreatic cancer, prompted us to investigate the potential role of DKK3 in PDAC development. Our preliminary findings suggest that DKK3 exerts stage, compartment, and even transcript-specific functions during PDAC progression. Intriguingly and challenging at the same time, DKK3 appears to operate either as a "friend" or as a "foe", depending on the spatiotemporal expression during pancreatic carcinogenesis. The current proposal aims at precise characterization of opposing functions of DKK3 during PDAC initiation and progression, and employs cutting-edge in vivo, in vitro, and ex vivo experimental settings at different stages of KRAS-driven tumorigenesis (from early dysplasia to cancer stage). Sophisticated investigations on genetically engineered mice involving time-resolved phenotyping and single-cell transcriptomic sequencing will aid in (i) capturing the minute dynamic of the DKK3 tumor suppressive functions; (ii) reveal ist interference with various signaling cascades over time and (iii) elucidate potential paracrine and autocrine crosstalks between stromal and tumor epithelial compartments. In vitro and ex vivo 3D co-culture experiments involving RNA interference and gene-rescue strategies will further substantiate the compartment and transcript-specific roles of DKK3. At the same time, a versatile ex vivo organ culture platform will enable long-term assessment of both early dysplastic events and tumor progression. Importantly, complex stem cell-derived pancreatic duct-like organoids mimicking tumor-initiating events will not only consolidate, but also translate our findings into a relevant human model. Altogether, the findings of this proposal will provide crucial and essential knowledge about DKK3, a protein featuring a double-edged sword role in carcinogenesis, that rises as a novel genuine biomarker and a promising therapeutic strategy in PDAC.