Project 2: Tumor Suppessive Role of ACER1 in Skin Cancer

项目摘要 皮肤鳞状细胞癌（CSCC）是最具侵袭性的非黑色素瘤皮肤癌， 在美国和全世界最常见的癌症。头颈部鳞状细胞癌（HNSCC）是癌症的主要原因 在美国，癌症占所有癌症的3 - 5%。这些癌症（SCC）共同促成了 发病率和死亡率。我们的长期目标是开发预防SCC的新方法 并在深入了解其发病机制的基础上进行治疗。此应用程序的具体目标是 定义了碱性神经酰胺酶1（ACER 1）的新型肿瘤抑制作用，该酶是碱性神经酰胺酶中的一员 神经酰胺酶家族，我们最初从酿酒酵母中鉴定，然后从 哺乳动物，在SCC的发展和进展。鳞状细胞癌起源于角质形成细胞或鳞状细胞， 包括肿瘤促进在内的多阶段过程。肿瘤促进改变控制细胞的基因表达 细胞增殖、分化和凋亡，这些基因的鉴定为化学预防提供了靶点 和/或治疗通过基因表达谱分析，我们发现12-O-十四酰基佛波醇-13-乙酸酯（TPA）， 典型的肿瘤促进剂，抑制正常表皮角质形成细胞中的ACER1表达。重要的是， 我们证明了在小鼠表皮中过表达人类ACER1转基因会增加肿瘤的发生， 潜伏期和减少肿瘤负荷的两阶段皮肤癌模型开始与7，12- 二甲基苯并（a）蒽（DMBA）和TPA促进，表明ACER1下调 有助于肿瘤的促进。与这一观点一致，我们发现ACER1的表达明显高于正常人。 在SCC细胞系和组织中被抑制，并且恢复ACER1表达抑制SCC的增殖 细胞，表明ACER1下调导致癌前病变和恶性肿瘤的过度增殖， 角质形成细胞，从而促进SCC的发展。基于这些重要的发现，我们假设， ACER1在SCC中作为肿瘤抑制因子，其下调通过以下方式促进皮肤肿瘤发生： 促进表皮角质细胞过度增殖。作为进一步的推论，我们假设，纠正 ACER1介导的通路将抑制皮肤肿瘤的发生。这些假设将通过两个具体目标进行检验。 在目的1中，我们将使用体外肿瘤模型和体外肿瘤模型来确定ACER1在SCC中的肿瘤抑制作用。 促进和皮肤肿瘤发生动物模型并建立ACER1/鞘脂的失调 信号通路是早发性SCC的预测性生物标志物。在目标2中，我们将定义细胞和分子 ACER1/鞘脂途径在SCC中作为肿瘤抑制因子发挥作用的机制。的 拟议的研究不仅将深入了解ACER1/鞘脂途径在SCC中的作用， 同时也是皮肤癌预防和治疗的知识框架。

PROJECT SUMMARY Cutaneous squamous cell carcinoma (CSCC), the most aggressive non-melanoma skin cancer, is the second most common cancer in the USA and worldwide. Head and neck SCC (HNSCC) is a leading cause of cancer deaths worldwide and accounts for 3-5% of all cancers in USA. Together, these cancers (SCC) contribute substantially to morbidity and mortality. Our long-term goal is to develop novel approaches to SCC prevention and treatment based on a deep understanding of its pathogenesis. The specific goal of this application is to define a novel tumor suppressive role for alkaline ceramidase 1 (ACER1), a member in the alkaline ceramidase family that we identified initially from the yeast Saccharomyces cerevisiae and then from mammals, in SCC development and progression. SCC arises from keratinocytes or squamous cells through a multistage process including tumor promotion. Tumor promotion alters the expression of genes controlling cell proliferation, differentiation, and apoptosis and identification of such genes offers targets for chemoprevention and/or therapy. Through gene expression profiling, we find that 12-O-tetradecanoylphorbol-13-acetate (TPA), the classic tumor promoter, inhibits the expression of ACER1 in normal epidermal keratinocytes. Importantly, we demonstrate that overexpression of the human ACER1 transgene in the mouse epidermis increases tumor latency and reduces tumor burden in the two-stage skin carcinogenesis model initiated with 7,12- dimethylbenz(a)anthracene (DMBA) and promoted with TPA, suggesting that ACER1 downregulation contributes to tumor promotion. Consistent with this notion, we show that ACER1 expression is markedly suppressed in SCC cell lines and tissues and that restoring ACER1 expression inhibits the proliferation of SCC cells, suggesting that ACER1 downregulation leads to the hyperproliferation of premalignant and malignant keratinocytes, thereby promoting SCC development. Based on these important findings, we hypothesize that ACER1 acts as a tumor suppressor in SCC and that its downregulation promotes skin tumorigenesis by promoting epidermal keratinocyte hyperproliferation. As a further corollary, we hypothesize that rectifying the ACER1 mediated pathway will inhibit skin tumorigenesis. These hypotheses will be tested by two specific aims. In Aim 1, we will define the tumor suppressive role for ACER1 in SCC using both in vitro model of tumor promotion and animal models of skin tumorigenesis and establish that dysregulation of the ACER1/sphingolipid pathway is a predictive biomarker for early onset SCC. In Aim 2 we will define the cellular and molecular mechanisms by which the ACER1/sphingolipid pathway functions as a tumor suppressor in SCC. The proposed research will provide not only insights into the role of the ACER1/sphingolipid pathway in SCC suppression but also an intellectual framework for skin cancer prevention and treatment.