Function of p73 in stemness/differentiation equilibrium and intratumoral cellular heterogeneity: mechanistic insights and anti-metastatic targeting

肿瘤是包含处于几种分化状态的异质细胞亚群的病理结构。能够自我更新和分化的大多数去分化和多能亚群是癌症干细胞（CSC）。最新的研究结果表明，CSC是一个多功能的亚群，未分化的干细胞样肿瘤细胞和分化的亚群之间的相互转化发生在肿瘤内，建立一个动态平衡。这种细胞身份的可塑性是由上皮-间充质转化（EMT）级联介导的，EMT级联在非CSC和CSC状态之间切换以促进癌症侵袭。靶向控制肿瘤的干性/分化平衡和燃料细胞异质性的机制是防止向转移阶段进展的有吸引力的策略。p73基因是一种p53同源基因，可产生抗癌（TAp 73）和致癌（DNp 73）亚型。我们提供了DNp 73以基于转录因子的作用模式诱导EMT介导的干性和攻击性的第一个证据。这是否是由分化的同时调节协调的，DNp 73如何改变肿瘤微环境以有利于转移，以及TAp 73是否拮抗这种作用，都是未知的。我们的初步数据预测，DNp 73驱动的干性伴随着神经分化的调节，支持最近认识到的，但仍然是谜一样的神经癌细胞串扰引起神经发生。这种DNp 73效应似乎严重依赖于一种未充分研究的基于蛋白质-蛋白质相互作用的机制，其中p73亚型可能与分化/神经发育因子相互作用，以p73反应元件依赖和独立的方式共同调节基因。在这个项目中，我们的目的是调查DNp 73对肿瘤内CSC/非CSC平衡和周围微环境相对于TAp 73的影响，并确定与侵袭性表型相关的辅助调节因子-靶基因轴。这些潜在的转移相关因子将在已建立的小鼠转移模型中进行功能表征，并在患者样品中进行验证。在结构系统药理学的帮助下，我们将重新利用或开发针对新发现的靶向复合物的药理学抑制剂。揭示p73介导的干细胞和分化的机制产生了对恶性转化过程的重要见解，并为抗转移治疗带来了巨大的希望。

Tumors are pathological structures encompassing heterogeneous cell subpopulations in several differentiation states. The most de-differentiated and pluripotent subpopulations capable of self-renewal and differentiation are cancer stem cells (CSCs). Latest findings suggest that CSCs are a versatile subpopulation and that interconversion between undifferentiated stem-like tumor cells and differentiated subpopulations occurs within the tumor establishing a dynamic balance. This plasticity in cellular identity is mediated by epithelial-mesenchymal transition (EMT) cascades, which switch between non-CSC and CSC states to facilitate cancer invasiveness. Targeting the mechanisms that control the stemness/differentiation equilibrium and fuel cellular heterogeneity of tumors is an appealing strategy to prevent progression towards metastatic stages. The p73 gene, a p53 homologue, generates both anti-oncogenic (TAp73) and oncogenic (DNp73) isoforms. We provided first evidence that DNp73 induces EMT-mediated stemness and aggressiveness in a transcription factor-based mode of action. Whether this is orchestrated by simultaneous modulation of differentiation, how DNp73 alters the tumor microenvironment in favor of metastasis, and if TAp73 antagonizes this effect, is unknown. Our preliminary data predict that DNp73-driven stemness is accompanied by regulation of neurodifferentiation, supporting a recently-recognized, but still enigmatic nerve-cancer cell cross-talk causing neoneurogenesis. This DNp73 effect seems to critically depend on an understudied protein-protein interaction-based mechanism, where p73 isoforms may interact with differentiation/neurodevelopmental factors to coregulate genes in a p73 responsive element-dependent and independent manner. In this project, we aim to investigate the effect of DNp73 on the intratumoral CSC/non-CSC equilibrium and in the surrounding microenvironment relative to TAp73 and to identify the coregulator-target gene axes associated with the aggressive phenotype. These potentially metastasis-relevant factors will be functionally characterized in established mouse metastasis models and validated on patient samples. Aided by structural systems pharmacology, we will repurpose or develop pharmacological inhibitors against newly uncovered target complexes. Unveilling the mechanisms of p73-mediated stemness and differentiation yields important insights into the process of malignant conversion and holds great promise for anti-metastatic therapies.