乙酰化酶NAT10调节p120-catenin在乳腺癌侵袭转移机制中的研究

Invasion and metastasis become the top causes of death for breast cancer as the female malignant tumor with the character of highest mortality. The remodeling and assembly of cytoskeletal proteins induced by RhoGTPases activation is a key step in promoting the invasion and metastasis of tumor cells, in which protein modifications such as phosphorylation and acetylation (and/or de-acetylation) play an important regulatory role. Some studies showed that HER2/ErbB2-induced breast cancer cell migration and invasion required p120 catenin activation of RhoGTPases and p120 catenin may be regulated by protein modification at this time, however, the details of regulation mechanisms are still unknown. In previous studies, we have reported that NAT10 as an acetyltransferase could have a redistribution from nucleolus to cytoplasm or membrane of colorectal cancer cells, which was caused by the activation of Wnt/β-catenin signaling pathway and enhance the ability of invasion and metastasis of tumor cells. Recent studies also showed that the translocation of NAT10 from nucleolus to cytoplasm or membrane existed in invasive breast cancer and promoted the p120-catenin expression in cytoplasm. We will make HER2-positive breast cancer as objects, adopt molecular biology, cell biology and molecular pathology, explore the interactions between NAT10 and p120 catenin, and their influence on the activation of RhoGTPases, and the remodeling or assembly of cellular cytoskeleton. The study is believed to provide more ideas for uncovering the molecular mechanism of cancer invasion and metastasis and more targets for anti-metastasis strategies.

乳腺癌的侵袭、转移是其成为女性致死率最高的恶性肿瘤的最主要原因。RhoGTPases激活所诱导的细胞骨架蛋白重组是促进肿瘤侵袭、转移的核心环节。研究表明HER2+乳腺癌侵袭和转移需要p120连环蛋白激活RhoGTPases介导，而p120可能受到蛋白修饰的调节作用，但具体机制不清。我们的前期工作证实，乙酰化酶NAT10在结直肠肿瘤中存在再分布现象，是由Wnt信号通路活化所导致，并且可增强肿瘤细胞侵袭与转移能力。预实验显示，NAT10在浸润性乳腺癌中也存在由核仁到胞浆胞膜的易位现象，且NAT10胞浆内聚集可增加p120表达。本研究拟在此基础上，以HER2+乳腺癌为研究对象，采用分子细胞生物学等技术，确定NAT10是否通过乙酰化p120激活RhoGTPases，调节细胞骨架蛋白重构而促进肿瘤细胞侵袭和转移。本研究将揭示NAT10调节肿瘤侵袭、转移的分子机制，并为寻找新的抗肿瘤转移靶点提供思路。

人N-乙酰转移酶10（N-acetyltransferase 10，NAT10，也称hALP：humam acetyltransferase-like protein）具有GNAT功能域，是A-型组蛋白乙酰化酶，可乙酰化组蛋白、微管蛋白及18S rRNA和tRNA。在各种肿瘤和早衰症中普遍表达。本课题主要研究NAT10在肿瘤侵袭转移中对细胞骨架的调节作用及机制。细胞骨架蛋白活动是肿瘤细胞侵袭、转移的基础。NAT10胞浆聚集可诱导微丝重构。免疫荧光显示NAT10胞浆聚集时，应力纤维和黏着斑减少，伪足增加，细胞移动性增强；当NAT10敲低时，可降低微丝重构。NAT10胞浆聚集可增加RhoGTPase表达，且体外GST-Pulldown实验证实，NAT10胞浆聚集能增加与GTP结合的活性RhoGTPase表达，证明NAT10可通过RhoGTPase调节微丝重构。但是NAT10可能并不是通过乙酰化Tiam1或GDIα调节RhoGTPase。而NAT10对p120-catenin的调节作用需要进一步深入研究证实。另一方面，NAT10胞浆聚集可增加微管蛋白乙酰化，并且其tRNA结合结构域对其乙酰化微管是必需的。被NAT10增加的乙酰化微管蛋白可以促进微触须形成。本研究发现NAT10通过调节细胞骨架蛋白，促进肿瘤细胞的侵袭和转移，为研究肿瘤侵袭、转移机制提供了线索。