Role of HDAC6 in platinum resistance of non-small cell lung cancer

描述（由申请人提供）：本项目的长期目标是阐明组蛋白去乙酰化酶6（HDAC 6）在非小细胞肺癌（NSCLC）铂类耐药中的作用。美国每年约有220，000名新的肺癌患者，这使得肺癌成为男性和女性癌症相关死亡的主要原因。肺癌治疗的两种一线方案是铂类与紫杉烷和铂类与吉西他滨。这些治疗的主要障碍之一是患者经常对铂产生耐药性。HDAC是从组蛋白和非组蛋白蛋白中去除乙酰基部分的酶，从而参与多种生物过程，包括转录调节、细胞生长/分化、凋亡等。HDAC抑制剂现在在肺癌治疗中具有很大的前景，部分原因在于它们能够恢复化学敏感性。然而，HDAC抑制剂增强化疗敏感性的机制在很大程度上是未知的。我们的初步数据表明，HDAC之一，称为HDAC 6，作为脱乙酰酶和泛素E3连接酶，以促进关键的DNA错配修复（MMR）蛋白MSH 2脱乙酰化，聚泛素化和降解。我们的研究结果还表明，MSH 2的去乙酰化下调MSH 2 MMR活性。此外，我们已经表明HDAC 6蛋白水平与15个NSCLC细胞系的顺铂耐药性呈正相关。由于MSH 2作为顺铂诱导的DNA加合物的传感器，MSH 2的缺失导致顺铂耐药，我们假设，由HDAC 6介导的脱乙酰化和泛素化控制的MSH 2蛋白水平下调及其MMR活性有助于铂耐药。因此，在本提案中，我们将首先表征HDAC 6泛素E3连接酶对MSH 2降解的活性，并研究HDAC 6介导的MSH 2脱乙酰化如何影响其MMR活性。然后，我们将在小鼠异种移植模型以及NSCLC患者的组织标本中验证HDAC 6在顺铂耐药性中的作用。我们的研究结果将确定HDAC 6作为肺癌治疗的新靶点，并表明HDAC 6和MSH 2可能作为NSCLC患者铂类耐药的生物标志物。我们的研究结果将建议临床相关的HDAC 6选择性抑制剂，抑制HDAC 6脱乙酰酶和E3连接酶的活性，用于治疗NSCLC的应用。

DESCRIPTION (provided by applicant): The long-term goal of this project is to elucidate the role of histone deacetylase 6 (HDAC6) in platinum resistance of non-small cell lung cancer (NSCLC). There are about 220,000 new lung cancer patients in the US annually which makes lung cancer the leading cause of cancer-related mortality in both men and women. Two first line regimens of lung cancer treatment are platinum with taxane and platinum with gemcitabine. One of the major obstacles of these treatments is that patients often develop resistance to platinum. HDACs are enzymes which remove acetyl moiety from histone and non-histone proteins, thereby being involved in a wide variety of biological processes including transcription regulation, cell growth/differentiation, apoptosis, etc. HDAC inhibitors now hold great promises in lung cancer treatment partly in that they are able to restore chemosensitivity. However, the mechanisms by which HDAC inhibitors enhance chemosensitivity are largely unknown. Our preliminary data has shown that one of the HDACs, termed HDAC6, acts as both a deacetylase and a ubiquitin E3 ligase to promote a key DNA mismatch repair (MMR) protein MSH2 deacetylation, polyubiquitination and degradation. Our results also indicate that deacetylation of MSH2 down-regulates MSH2 MMR activity. Moreover, we have shown that HDAC6 protein levels positively correlate with cisplatin resistance in a panel of 15 NSCLC cell lines. Given the fact that MSH2 serves as a sensor for cisplatin-induced DNA adducts and loss of MSH2 causes cisplatin resistance, we hypothesize that down-regulation of MSH2 protein level and its MMR activity governed by HDAC6-mediated deacetylation and ubiquitination contributes to platinum resistance. Therefore, in this proposal, we will first characterize HDAC6 ubiquitin E3 ligase activity towards MSH2 degradation and investigate how HDAC6-mediated deacetylation of MSH2 affects its MMR activity. We will then validate the role of HDAC6 in cisplatin resistance in a mouse xenograft model as well as in NSCLC patients' tissue specimens. The results of our research will identify HDAC6 as a novel therapeutic target in lung cancer treatment and show that HDAC6 and MSH2 may serve as biomarkers for platinum resistance in NSCLC patients. Our results will suggest the application of clinically relevant HDAC6-selective inhibitors which suppress HDAC6 deacetylase and E3 ligase activity for the treatment of NSCLC.