微管结合蛋白HN1在未分化甲状腺癌失分化中的作用及机制研究

Anaplastic thyroid carcinoma (ATC) is one of the most deadly endocrine cancers, and its dedifferentiation is an important malignant feature, while the molecular mechanism remains unknown. Reprogramming is the key process for determining cell fate, among which acetylation modification-mediated cytoskeletal dynamic is of great significance. Based on clinical proteomics analysis, we found that the microtubule associated protein HN1 was highly expressed in ATC tissues. HN1 knockout can induce the differentiation of ATC cells, and attenuated their migration and invasion. Moreover, suppressing the expression of HN1 also reduced the ability of tumor formation in vivo. Further study showed that HN1 could interact with microtubule depolymerized protein STMN1, inhibiting HN1 expression significantly upregulated microtubule acetylation and promoted microtubule stabilization. These results suggest that HN1 is a key protein regulating the dedifferentiation of ATC and may be a potential target for the treatment of ATC. Thus, the project will further study the correlation between HN1 expression and microtubule acetylation levels based on clinical samples. Secondly, we will also elucidate that HN1 regulates microtubule depolymerization is the key to maintaining ATC dedifferentiation. Finally, the mechanism of HN1-STMN1 interaction and its role in inhibition of α-tubulin acetylation will be researched at the molecular and cellular levels. Our results aim at revealing the intrinsic mechanisms of HN1 in maintaining ATC dedifferentiation, and providing potential target for the treatment of ATC.

未分化甲状腺癌（ATC）是恶性程度最高的内分泌肿瘤之一，失分化是其重要恶性特征，但分子机制未明。重编程是细胞命运改变的关键过程，乙酰化介导的细胞骨架重排在该过程中具有重要意义。项目组前期基于临床的蛋白组学比对分析发现，微管结合蛋白HN1在ATC组织特异高表达。敲降HN1可促进ATC细胞分化，抑制其迁移和侵袭，降低体内成瘤能力。生化研究显示HN1与微管解聚蛋白STMN1相互作用，且抑制HN1表达显著上调微管乙酰化，促微管稳定。所获结果提示HN1是调控ATC失分化的关键蛋白，且可能是治疗ATC的潜在靶点。基于此，项目组将基于临床样本进一步明确HN1表达和微管乙酰化水平的相关性；并确证HN1调控微管解聚是维持ATC失分化的关键；进而从机制角度阐述HN1-STMN1相互作用及在微管乙酰化中的调控作用。研究预期阐明HN1维持ATC失分化的作用与机制，为ATC治疗靶点发现提供理论基础和实验依据。

未分化甲状腺癌（ATC）是恶性程度最高的内分泌肿瘤，失分化是其重要恶性特征，但分子机制未明。越来越多的研究表明重新诱导ATC分化是其治疗的重要策略之一。重编程是细胞命运改变的关键过程，乙酰化介导的细胞骨架重排在该过程中具有重要意义，寻找细胞重编程的关键驱动因子有望逆转ATC失分化状态。本项目围绕HN1如何调控微管蛋白稳态进行系统的研究，旨在揭示HN1介导ATC失分化作用及机制。项目研究结果表明，HN1在甲状腺癌组织中高表达，并与患者预后负相关。基因芯片分析确证HN1表达与甲状腺功能蛋白及甲状腺分化转录因子存在显著负相关。敲降HN1可显著恢复ATC细胞的甲状腺功能蛋白及甲状腺分化转录因子表达水平。进一步研究表明，HN1与维持甲状腺癌细胞侵袭、迁移等恶性表型相关，且敲除HN1可显著抑制TGFβ诱导的EMT进程。动物实验表明敲除HN1可显著抑制ATC成瘤，并诱导ATC肿瘤细胞重新分化，抑制EMT标志物及MMP9等迁移相关标志物的表达。机制研究显示，HN1敲除后可显著上调ATC细胞微管乙酰化水平，反之亦然。进一步研究发现HN1与STMN1存在相互作用，且HN1与STMN1的结合随甲状腺癌的恶性程度逐渐增加，其中HN1(1-80aa)及HN1(81-154aa)截短片段均可与STMN1结合。深入研究提示，HN1通过稳定STMN1，减少UBQLN1介导的STMN1泛素化，进而调控微管蛋白乙酰化。本项目阐明了微管结合蛋白HN1可通过结合STMN1，下调微管蛋白α-tubulin乙酰化水平，进而抑制微管蛋白聚合，最终诱导ATC细胞形态改变及分化标志物丢失，促使ATC失分化。所获结果可望为逆转ATC失分化治疗策略提供理论依据，也为ATC的治疗提供潜在新靶点。