Project 2: Role of ACER2 in Liver Cancer

摘要 肝细胞癌（HCC）是一种主要类型的肝癌，是全球癌症死亡的主要原因。 HCC对大多数治疗选择仍然是难治的;因此，迫切需要新的治疗方式。我们 长期目标是在深入了解其发病机制的基础上开发新的HCC治疗方法。的 本申请的具体目标是确定碱性神经酰胺酶2的新的肿瘤抑制作用 （ACER 2）通路在HCC发展和进展中的作用。ACER 2是碱性神经酰胺酶家族的成员 我们最初从酿酒酵母中发现，然后从哺乳动物中发现。ACER 2催化 神经酰胺水解产生鞘氨醇（SPH），一种与程序性细胞死亡有关的生物活性脂质 (PCD)和自噬。我们鉴定了ACER 2作为p53的一个新的转录靶点，并证明了ACER 2在p53基因中的作用。 ACER 2/SPH通路是一种新的信号传导轴，其在p53下游操作以介导PCD响应于 DNA损伤。根据TCGA数据库，ACER 2在几种癌症中突变或缺失抑制。 先前的研究发现，在HCC中，ACER 2被表观遗传抑制，我们的初步结果显示， 与患者匹配的邻近非肿瘤肝组织相比，肝肿瘤中的ACER 2下调。 值得注意的是，我们发现缺乏碱性神经酰胺酶2（Acer 2）基因的小鼠更容易受到年龄的影响。 各种自发性肿瘤类型（包括肝肿瘤）的相关发展，表明ACER 2是一种 新型肿瘤抑制剂。根据这些令人兴奋的发现，我们假设ACER 2是一种新的肿瘤， 一种抑制因子，其抑制可促进HCC的发生、发展和对DNA损伤的抵抗 化疗药物作为进一步的推论，我们假设纠正ACER 2/SPH通路将抑制 肝癌和克服肝癌对化疗药物的耐药性。这些假设将在三个测试 相关的具体目的：目的1：利用肝细胞化学方法，确定ACER 2在HCC中发挥关键的肿瘤抑制作用。 目的2：通过建立肝癌小鼠模型和肝类器官模型，明确肝癌发生的细胞和分子机制。 其中ACER 2/SPH通路的抑制促进了肝脏肿瘤的发生，目的3建立ACER 2/SPH通路的作用。 ACER 2通路在提高肝癌放化疗疗效中的作用。成功实现这些目标将：（1） 验证新发现的肿瘤抑制因子ACER 2的肿瘤抑制作用; 2）提供新的见解， 新发现的p53/ACER 2/SPH信号轴介导DNA损伤的机制 反应和肿瘤抑制;和3）提供了将ACER 2/SPH途径发展成一种新的治疗方法的概念证明。 HCC的新治疗靶点。鉴于HCC患者的临床结局较差，这些研究可能 对这些患者的临床管理产生广泛影响。

Abstract Hepatocellular carcinoma (HCC), a major type of liver cancer, is a leading cause of cancer deaths worldwide. HCC remains refractory to most treatment options; hence, new therapeutic modalities are urgently needed. Our long-term goal is to develop novel HCC therapeutics based on a deep understanding of its pathogenesis. The specific goal of this application is to define a novel tumor suppressive role for the alkaline ceramidase 2 (ACER2) pathway in HCC development and progression. ACER2 is a member in the alkaline ceramidase family that we identified initially from the yeast Saccharomyces cerevisiae and then from mammals. ACER2 catalyzes the hydrolysis of ceramides to generate sphingosine (SPH), a bioactive lipid implicated in programmed cell death (PCD) and autophagy. We identify ACER2 as a novel transcriptional target of p53 and demonstrate that the ACER2/SPH pathway is a novel signaling axis that operates downstream of p53 to mediate PCD in response to DNA damage. According to the TCGA database, ACER2 is mutated or deleted suppressed in several cancers. A previous study finds that ACER2 is epigenetically repressed in HCC and our preliminary results reveal that ACER2 is downregulated in liver tumors compared to patient-matched adjacent non-tumor liver tissues. Remarkably, we find that mice deficient in the alkaline ceramidase 2 (Acer2) gene are more susceptible to age- related development of various spontaneous tumor types including liver tumors, suggesting that ACER2 is a novel tumor suppressor. According to these exciting findings, we hypothesize that ACER2 is a novel tumor suppressor whose suppression promotes HCC development, progression, and resistance to DNA-damaging chemotherapeutics. As a further corollary, we hypothesize that rectifying the ACER2/SPH pathway will inhibit HCC and overcome the resistance of HCC to chemotherapeutics. These hypotheses will be tested in three interrelated specific aims: Aim 1 Establish that ACER2 plays a key tumor suppressive role in HCC using a liver carcinogenesis mouse model and liver organoid model, Aim 2 Define the cellular and molecular mechanisms by which the repression of the ACER2/SPH pathway promotes liver tumorigenesis, and Aim 3 Establish the role of the ACER2 pathway in improving the radio/chemotherapy of HCC. Successful completion of these aims will 1) validate the tumor suppressive role of the newly-identified tumor suppressor ACER2; 2) offer novel insights into the mechanisms by which the newly identified p53/ACER2/SPH signaling axis mediates the DNA damage response and tumor suppression; and 3) provide a proof of concept to develop the ACER2/SPH pathway into a novel therapeutic target for HCC. Given the poor clinical outcome of patients with HCC, these studies may have widespread impact on the clinical management of these patients.