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率的主要原因之一，5年生存率低于10%。尽管进行了广泛的研究，但仍然缺乏用于早期疾病检测和病理生理学的可靠生物标志物。因此，详细描述PDAC不同区室之间肿瘤内相互作用的密切分子机制变得至关重要。DKK 3（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质：在PDAC中，在Trp 53缺陷的情况下抑制DKK 3会对肿瘤进展和肿瘤存活产生负面影响。值得注意的是，DKK 3过表达使PDAC对吉西他滨治疗敏感。我们先前将DKK 3鉴定为胰腺炎期间器官再生的新因子，并且通过涉及一组体内模型的最新研究，描绘了DKK 3与经典Wnt和Hedgehog信号传导之间的直接的、先前未知的联系。鉴于胰腺炎是胰腺癌的危险因素，这促使我们研究DKK 3在PDAC发展中的潜在作用。我们的初步研究结果表明，DKK 3在PDAC进展过程中发挥阶段，区室，甚至转录特异性功能。有趣和具有挑战性的是，DKK 3似乎既可以作为“朋友”也可以作为“敌人”，这取决于胰腺癌发生过程中的时空表达。目前的提案旨在精确表征PDAC启动和进展期间DKK 3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，体外和离体实验环境。涉及时间分辨表型分析和单细胞转录组测序的基因工程小鼠的复杂研究将有助于（i）捕获DKK 3肿瘤抑制功能的微小动态;（ii）揭示随时间推移对各种信号级联的干扰，以及（iii）阐明基质和肿瘤上皮隔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DKK 3的区室和转录特异性作用。同时，多功能的离体器官培养平台将能够长期评估早期发育异常事件和肿瘤进展。重要的是，复杂的干细胞衍生的胰管样类器官模拟肿瘤启动事件不仅会巩固，而且会将我们的发现转化为相关的人类模型。总而言之，这项提案的发现将提供关于DKK 3的关键和基本知识，DKK 3是一种在致癌作用中具有双刃剑作用的蛋白质，它将成为PDAC中一种新的真正的生物标志物和有前途的治疗策略。

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.