Hedgehog Acyltransferase as a target in cancer

描述（由申请人提供）：拟议研究的目标是开发治疗试剂以阻断Sonic hedgehog（Shh）的信号传导。异常Shh表达与胰腺癌有关，胰腺癌是美国癌症相关死亡的第四大原因。为了发出信号，Shh必须通过将脂肪酸棕榈酸酯连接到其N-末端来修饰。我们的目标是利用Shh棕榈酰化作为一个潜在的阿喀琉斯之踵，通过靶向Hhat（刺猬酰基转移酶），催化棕榈酸酯附着到Shh的酶。我们的实验室使用高通量筛选来鉴定RU-SKI 43，这是一种新型的、一流的小分子Hhat抑制剂，其阻断Shh棕榈酰化、自分泌和旁分泌Shh信号传导以及人胰腺癌细胞生长。我们的目标是进一步将Hhat抑制剂开发成有效治疗胰腺癌和其他癌症的新型化学治疗剂。 这一提议也挑战了Shh在胰腺癌中的作用仅限于向间质的旁分泌信号传导的教条。我们有数据表明，胰腺肿瘤细胞确实对Shh有反应，但通过非经典的，Smoothened独立的途径。目前在临床试验中的所有Shh通路抑制剂都针对Smoothened。拟议中的R21项目有可能通过将焦点带回肿瘤靶点来设定治疗的新方向。 上皮细胞 目标1。优化Hhat抑制剂以调节Shh棕榈酰化和信号传导 Hhat抑制剂的作用机制将通过监测胰腺癌细胞以及雌激素受体阳性乳腺癌细胞中由Hhat和Shh调节的信号传导途径来确定。接下来，我们将致力于优化新的第二代Hhat抑制剂，其在体外抑制Shh棕榈酰化方面的效力比RU-SKI 43高出70倍，但体内半衰期短。药物和合成化学家开发的结构-活性关系和药效团模型将用于合理设计和合成第三代及以后的Hhat抑制剂，其具有更高的效力和生物利用度。将评估这些抑制剂在体外阻断Shh棕榈酰化、Shh信号传导和人胰腺癌细胞生长的功效。 目标二。作为治疗剂的Hhat抑制剂在体内阻断Shh驱动的癌症 为此目的的实验将致力于通过评估化合物的药代动力学和药效学（ADME/PK/TOX）来优化Hhat抑制剂向动物的递送。将评估Hhat抑制剂在胰腺癌的小鼠异种移植模型中以及在K-RasG 12 D/p53 R172 H小鼠（胰腺癌的基因工程小鼠模型）中阻断肿瘤发生的能力。

DESCRIPTION (provided by applicant): The goal of the proposed research is to develop therapeutic reagents to block signaling by Sonic hedgehog (Shh). Aberrant Shh expression is implicated in pancreatic cancer, the 4th leading cause of cancer-related deaths in the US. In order to signal, Shh must be modified by attachment of the fatty acid palmitate to its N-terminus. We aim to exploit Shh palmitoylation as a potential Achilles heel by targeting Hhat (Hedgehog acyltransferase), the enzyme that catalyzes attachment of palmitate to Shh. Our laboratory used high throughput screening to identify RU-SKI 43, a novel, first-in-class small molecule Hhat inhibitor that blocks Shh palmitoylation, autocrine and paracrine Shh signaling, and human pancreatic cancer cell growth. We aim to further develop Hhat inhibitors into novel chemotherapeutics efficacious for the treatment of pancreatic and other cancers. This proposal also challenges the dogma that Shh action in pancreatic cancer is limited to paracrine signaling to the stroma. We have data that pancreatic tumor cells do indeed respond to Shh but via non-canonical, Smoothened-independent pathways. All of the Shh pathway inhibitors currently in clinical trials target Smoothened. The proposed R21 project has the potential to set a new direction in therapeutics by bringing the focus back to targets in the tumor epithelial cells. Aim 1. Optimization of Hhat inhibitors to regulate Shh palmitoylation and signaling The mechanism of action of Hhat inhibitors will be determined by monitoring signaling pathways regulated by Hhat and Shh in pancreatic cancer cells, as well as in estrogen-receptor positive breast cancer cells. Next, we will work on optimizing new, 2nd generation Hhat inhibitors that are up to 70x more potent than RU-SKI 43 in inhibiting Shh palmitoylation in vitro, but have short in vivo half-lives. Structure- activity relationships and a pharmacophore model developed by medicinal and synthetic chemists will be used for rational design and synthesis of 3rd generation and beyond Hhat inhibitors with increased potency and bioavailability. The efficacy of these inhibitors for blocking Shh palmitoylation, Shh signaling, and growth of human pancreatic cancer cells in vitro will be assessed. Aim 2. Hhat inhibitors as therapeutic agents to block Shh-driven cancers in vivo Experiments in this aim will be devoted to optimizing delivery of Hhat inhibitors into animals, by assessing pharmacokinetics and pharmacodynamics (ADME/PK/TOX) of the compounds. The ability of Hhat inhibitors to block tumorigenesis in a mouse xenograft model of pancreatic cancer, as well as in K- RasG12D/p53R172H mice, a genetically engineered mouse model of pancreatic cancer, will be assessed.