Epigenetic Control of HPV-associated Oral Carcinogenesis

描述（由申请人提供）：本申请的长期目标是了解表观遗传机制如何控制高危人乳头瘤病毒（HPV）相关的口腔癌发生。鳞状细胞癌（SCC）是口腔、口咽、头颈部最常见的癌症。HPV16是一种小的DNA病毒，具有鳞状上皮的亲和性，已被发现与口腔和口咽鳞状细胞癌（OSCC）的发生和进展有关。更重要的是，在过去的十年中，hpv阳性OSCC的发病率在美国有所增加。高危型HPV16表达两种主要的癌蛋白E6和E7。E6和E7的结合（E6/E7）能使人口腔角化细胞永生化并促进肿瘤的发生。虽然在了解E6/ e7介导的OSCC发展的分子控制方面取得了重大进展，但对于HPV感染与口腔角化细胞染色质动力学在OSCC发展和进展中的相互作用知之甚少。组蛋白甲基化是一个与基因表达激活和抑制相关的重要过程，因此在细胞生长控制和肿瘤发生中起着关键作用。为了探索hpv相关OSCC的表观遗传调控，我们系统地分析了表达E6/ e7的OSCC细胞中组蛋白去甲基化酶的表达。有趣的是，我们发现E6/E7在OSCC细胞中有效抑制KDM5C（也称为SMCX）的表达。KDM5C是一种组蛋白去甲基化酶，可去除赖氨酸4处三甲基化的组蛋白H3 （H3K4me3）。H3K4me3是一种激活标记物，抑制KDM5C可使H3K4me3水平升高，导致基因活化。作为基因表达谱的补充方法，我们的siRNA筛选已经发现组蛋白去甲基化酶KDM4A通过去除H3K9me3在AP-1的表观遗传激活中起重要作用。之前，我们发现AP-1在OSCC的侵袭性生长中起关键作用，这是原位癌向OSCC发展所必需的。除了控制E6/E7转录外，AP-1在hpv介导的肿瘤发生中起重要作用。基于我们令人兴奋的初步研究，在这个新的应用中，我们的新假设是KDM5C和KDM4A通过修饰H3K4me3和H3K9me3标记从表观遗传学上控制hpv阳性OSCC的发生和进展。为了验证我们的假设，提出了三个具体目标。目的1是确定高危HPV16 E6/E7癌蛋白是否通过抑制KDM5C在表观遗传学上重编程OSCC并促进OSCC进展。目的2是确定KDM4A是否通过AP-1在表观遗传学上促进E6/E7的表达。目的3：确定E6/E7是否通过KDM4A激活AP-1并促进OSCC的发展。由于组蛋白去甲基化酶是可化学修饰的，KDM5C和KDM4A可能是特异性控制hpv相关OSCC的新治疗靶点。

DESCRIPTION (provided by applicant): The long-term objectives of this application are to understand how epigenetic mechanisms control the high-risk human papillomaviruses (HPV)-associated oral carcinogenesis. Squamous cell carcinoma (SCC) is the most common cancer arising in the oral cavity, oropharynx, head and neck. The high-risk HPV16, a small DNA virus having tropism for squamous epithelia, has been found to be associated with the development and progression of oral and oropharyngeal SCC (OSCC). More importantly, the incidence of HPV-positive OSCC has increased in the USA in the last decade. The high-risk HPV16 expresses two major oncoproteins, E6 and E7. The combination of E6 and E7 (E6/E7) potently immortalizes human oral keratinocytes and promotes oncogenesis. While significant progress has been made in understanding the molecular control of E6/E7-mediated OSCC development, little is known about the interplay between HPV infection and oral keratinocyte chromatin dynamics in OSCC development and progression. Histone methylation is an important process linked to the activation and repression of gene expression, thus playing a critical role in cell growth control and oncogenesis. To explore the epigenetic regulation of HPV-associated OSCC, we systemically profiled the expression of histone demethylases in E6/E7-expressing OSCC cells. Interestingly, we found that E6/E7 potently suppressed KDM5C (also known as SMCX) expression in OSCC cells. KDM5C is a histone demethylase which removes trimethylated histone H3 at lysine 4 (H3K4me3). H3K4me3 is an activation marker, and the inhibition of KDM5C can increase the levels of H3K4me3, leading to gene activation. As a complementary approach to gene expression profiling, our siRNA screening has identified that the histone demethylase KDM4A plays an important role in the epigenetic activation of AP-1 by removing H3K9me3. Previously, we have found that AP-1 plays a critical role in the invasive growth of OSCC which is required for the progression of carcinoma in situ to OSCC. In addition to control of E6/E7 transcription, AP-1 plays an essential role in HPV-mediated oncogenesis. Based on our exciting preliminary studies, in this new application, our novel hypothesis is that KDM5C and KDM4A epigenetically control development and progression of HPV-positive OSCC by modifying H3K4me3 and H3K9me3 marks. Three specific aims are proposed to test our hypothesis. Aim 1 is to determine whether the high-risk HPV16 E6/E7 oncoproteins epigenetically reprogram OSCCs and promote OSCC progression by inhibiting KDM5C. Aim 2 is to determine whether KDM4A epigenetically promotes E6/E7 expression through AP-1. Aim 3 is to determine whether E6/E7 activate AP-1 and promote OSCC development through KDM4A. Since histone demethylases are chemically modifiable, KDM5C and KDM4A might represent novel therapeutic targets for specifically controlling HPV-associated OSCC.