The role of UTX in Epidermal Homeostasis, Carcinogenesis, and Sex Mediated Risk of Cutaneous Squamous Cell Carcinoma

摘要 组蛋白修饰剂是所有形式的癌症中最高度突变的基因之一，其中组蛋白修饰剂是一种具有高活性的基因。 脱甲基酶UTX（KDM 6A）是最常见的酶之一。UTX在几种上皮癌中发生突变 包括皮肤鳞状细胞癌（cSCC），其是所有人类肿瘤中第二常见的类型。 恶性肿瘤。UTX存在于X染色体上，是一种主要的增强子调节剂。它确立了积极的 增强子景观通过其组蛋白去甲基化酶活性以及其与其他蛋白复合的能力， 激活组蛋白修饰剂。还已知UTX逃避X失活，从而产生剂量差异。 男性和女性，这可能解释了观察到的风险和 某些类型癌症的严重程度，包括cSCC。为了支持这一点，当所有人都被淘汰时， 组织中，UTX损失导致所有雌性的胚胎死亡，而约25%的雄性存活至成年。 有趣的是，UTY，UTX的Y-连接的paraminase，保留了最小的脱甲基酶功能，但潜在的 通过其他机制补偿UTX的损失。除了涉及性别特异性， 尽管存在差异，UTX在几种上皮癌中被认为是肿瘤抑制因子。最近，UTX还 能够感知细胞内的氧气积累的数据表明，UTX对于适当的蜂窝通信至关重要。 体内平衡，并在发育和癌变中发挥重要作用。然而，尽管有这些证据 以及cSCC中UTX突变的高发生率，实际上还不了解这种酶如何 在表皮稳态和癌变过程中起作用。为了研究这一点，我们已经产生了小鼠， 表皮特异性Utx缺失，其中仅雌性Utx敲除小鼠显示任何明显异常。 具体来说，纯合子基因敲除雌性小鼠的体型缩小，皮肤粗糙，鳞状 与同窝对照相比。从这些小鼠收集的皮肤的H&E染色显示癌前病变 表皮增生等变化。当在原代人角质形成细胞中被敲除时，UTX损失导致 到戏剧性的转录变化。低血糖反应基因和参与氧化磷酸化的基因是 是最有差异的表达之一。这些数据引发了这样的假设，即UTX对于适当的 稳态基因表达，当丢失时会导致代谢改变和更高的癌症风险。为了验证这一 假设，我将实现以下目标：在目标1中，我将确定Utx损失如何影响表皮 体内稳态，并研究其在表皮缺氧和代谢中的作用。在Aim 2中，我将使用UV- 在我们的Utx基因敲除小鼠模型中诱导肿瘤发生，以确定Utx是否作为肿瘤 表皮中的抑制因子。我还将评估肿瘤风险和严重程度如何受到Utx损失的影响， 男性和女性收集关于UTX拷贝基因剂量驱动的性别特异性差异的见解。 此外，鉴于表观遗传变化的内在可逆性，这些研究有望提供新的 深入了解表观遗传疗法治疗这些极其常见的癌症的潜力。

ABSTRACT Histone modifiers are amongst the most highly mutated genes in all forms of cancer, with the histone demethylase UTX (KDM6A) being one of the most frequent. UTX is mutated in several epithelial cancers including cutaneous squamous cell carcinoma (cSCC), the second most common type of all human malignancies. UTX is found on the X chromosome and is a major enhancer regulator. It establishes the active enhancer landscape through its histone demethylase activity as well as its ability to complex with other activating histone modifiers. UTX is also known to escape X inactivation creating a dosage disparity between males and females that may account for some of the sex specific differences observed for both the risk and severity of certain types of cancer, including cSCC. In support of this, when constitutively knocked out in all tissues, UTX loss results in embryonic lethality in all females, while ~25% of males survive to adulthood. Interestingly, UTY, the Y-linked paralog of UTX, retains minimal demethylase function but potentially compensates for loss of UTX through other mechanisms. In addition to its involvement in sex specific differences, UTX is implicated as a tumor suppressor in several epithelial cancers. Recently, UTX has also been shown to sense cellular oxygen. Accumulating data suggests that UTX is critical for proper cellular homeostasis and plays fundamental roles in development and carcinogenesis. However, despite this evidence and the high incidence of UTX mutations in cSCC, there is virtually no understanding of how this enzyme functions during epidermal homeostasis and carcinogenesis. To investigate this, we have generated mice with epidermal specific deletions of Utx where only female Utx knockout mice display any obvious abnormalities. Specifically, homozygous knockout female mice present with reduced size as well as erythematous, scaly skin compared to littermate controls. H&E staining of the skin harvested from these mice reveals premalignant changes such as epidermal hyperplasia. When knocked down in primary human keratinocytes UTX loss leads to dramatic transcriptional changes. Hypoxic response genes and those involved oxidative phosphorylation are among the most differentially expressed. These data provoke the hypothesis that UTX is critical for the proper homeostatic gene expression, and when lost lead to altered metabolism and higher cancer risk. To test this hypothesis, I will carry out the following aims: In Aim1 I will determine how Utx loss affects epidermal homeostasis in vivo and investigate its role in hypoxia and metabolism in the epidermis. In Aim2 I will use UV- radiation to induce tumorigenesis in our Utx knockout mouse model to determine if Utx acts as a tumor suppressor in the epidermis. I will also assess how tumor risk and severity is affected by Utx loss between males and females to glean insights about sex specific differences driven by UTX copy gene dosage. Furthermore, given the inherent reversibility of epigenetic changes, these studies hold promise to provide new insight into the potential for epigenetic therapies for these incredibly common cancers.