The role of the EMT-inducer Zeb1 in the invasive tumor stroma during colon cancer progression

恶性肿瘤的进展依赖于侵袭性细胞特征的(瞬时)获得，但我们仍然不完全了解潜在的调控机制。转化生长因子在结直肠癌的发生发展中起着不同的作用，可能是早期的肿瘤抑制因子，也可能是晚期侵袭转移的控制因子。此外，转化生长因子通过募集肿瘤相关成纤维细胞(CAF)对肿瘤微环境产生重要影响。成纤维细胞含量高与肿瘤预后不良有关，CAF可通过免疫抑制直接或间接促进肿瘤生长。然而，目前尚不清楚哪些特殊的成纤维细胞群参与其中，以及它们的形成和可塑性是如何控制的。ZEB1被认为是转化生长因子β的关键下游因子，是肿瘤细胞上皮-间充质转化的主要调节因子。此外，ZEB1在CAF的一个子集中也有显著的表达。在这里，我们建立了组织特异性基因敲除和共培养/移植模型，以解决ZEB1在CAF中的作用。我们的初步结果表明，在结肠炎相关癌症模型中，成纤维细胞特异性缺失ZEB1通过减弱肿瘤抑制环境来促进原发肿瘤的生长。用肿瘤类器官进行的共培养实验显示，ZEB1缺陷的成纤维细胞的壁龛功能发生了变化，可塑性受损。我们将利用侵袭性小鼠结肠癌模型来表征间质ZEB1对肿瘤微环境的影响。成纤维细胞亚型和免疫细胞募集将通过单细胞RNA测序进行研究。器官共培养和移植模型将用于旁分泌细胞相互作用的机械解剖。随后，我们将使用人类结直肠癌样本和临床数据集来测试ZEB1依赖的成纤维细胞可塑性的调节是否可能提供一种治疗选择。

Malignant tumor progression depends on the (transient) acquisition of invasive cellular traits, but we still do not fully understand the underlying regulatory mechanisms. TGFß signaling plays diverse roles during colorectal carcinoma (CRC) progression and may act as an early tumor suppressor or later control invasion and metastasis. In addition, TGFß critically influences the tumor microenvironment, e.g. by recruitment of cancer-associated fibroblasts (CAFs). A high fibroblast content is associated with poor tumor prognosis and CAFs may promote tumor growth directly or indirectly by causing immunosuppression. However, it is currently unknown, which specialized fibroblast populations are involved, and how their formation and plasticity is controlled. Zeb1 has been identified as key downstream factor of TGFβ and master regulator of epithelial-mesenchymal transition (EMT) in tumor cells. In addition, Zeb1 shows prominent expression in a subset of CAFs. Here, we have established tissue-specific knock-out and co-culture/transplantation models to address the role of Zeb1 in CAFs. Our preliminary results show that fibroblast-specific depletion of Zeb1 enhances primary tumor growth by attenuating a tumor-suppressive environment in a colitis-associated cancer model. Co-culture experiments using tumor organoids showed altered niche function and impaired plasticity of Zeb1 deficient fibroblasts. We will characterize the impact of stromal Zeb1 on the tumor microenvironment using invasive mouse models of colon cancer. Fibroblast subtypes and immune cell recruitment will be studied by single cell RNA sequencing. Organoid co-culture and transplantation models will be used for mechanistic dissection of the paracrine cell interactions. Subsequently we will use human CRC samples and clinical data sets to test whether modulation of ZEB1-dependent fibroblast plasticity may offer a therapeutic option.