A Novel Druggable Epigenetic Vulnerability Pathway in HCC

项目摘要 仅在美国，肝细胞癌（HCC）每年就造成近29，000例死亡。 然而，驱动HCC发展的分子机制仍然难以捉摸，目前的HCC治疗方法 临床获益微不足道。表观遗传学沉默HCC肿瘤抑制基因的因素具有 潜在的促进肿瘤发生，因此可能为HCC治疗提供新的药物靶点。去发现 这些因素，我们进行了一个创新的全基因组人类RNA干扰（RNAi）筛选，以确定 介导HCC肿瘤抑制基因Hedgehog相互作用蛋白表观遗传沉默的因素 （HHIP）。HHIP是Sonic hedgehog（SHH）信号传导的负调节因子，并且由于表观遗传学的原因而导致HHIP的丧失。 沉默异常激活SHH信号传导，已经提出在多种肿瘤中促进肿瘤生长。 癌症，包括HCC。在我们的筛选中确定的因子之一是CDC样激酶1（CLK 1），一种双功能蛋白激酶。 磷酸化参与前体mRNA剪接的富含丝氨酸/丝氨酸的蛋白质的特异性蛋白激酶。我们 发现CLK 1转化培养的永生化肝细胞并促进小鼠HCC肿瘤生长 在皮下异种移植物中，这些作用依赖于CLK 1蛋白激酶活性。值得注意的是， HHIP和CLK 1过表达的表观遗传沉默在HCC患者样品中频繁发生，支持 我们研究结果的临床意义基于这些共同的发现，我们假设CLK 1是一个驱动程序， HCC通过表观遗传学沉默肿瘤抑制因子HHIP发挥作用。实验结果 本申请中提出的方法将确立CLK 1作为HCC驱动因子的作用，通过以下方式确定机制： 其中CLK 1促进肿瘤生长，并评估CLK 1作为HCC治疗的药物靶点。在目标1中，我们 使用一系列的方法来确定CLK 1在肝肿瘤发生的起始和进展中的作用。 互补的小鼠模型，概括了HCC的特征。在目标2中，我们将测试 假设CLK 1通过HHIP的表观遗传沉默促进肝肿瘤生长，导致 SHH信号的异常激活。我们还将研究其他机制，其中CLK 1可能促进 肿瘤生长在目标3中，我们将评估CLK 1作为开发肝癌治疗方法的新型药物靶点。 在初步的实验中，我们发现，抑制CLK 1可以增强自然杀伤细胞（NK）介导的免疫应答。 根除HCC细胞。因此，我们预测，通过药理学抑制CLK 1 将：（1）通过阻断致癌SHH信号直接抑制肿瘤生长，和（2）增加NK细胞介导的 根除肿瘤细胞。为了测试这些预测，我们将确定高度特异性的CLK 1小 分子抑制剂KH-CB 19能有效抑制肝肿瘤生长，增强NK细胞杀伤能力 使用互补系列的免疫受损和免疫活性小鼠来根除肿瘤， HCC模型总的来说，本申请中提出的实验结果将阐明一种新颖的方法。 药物途径，促进HCC的发展和评估治疗HCC的新方法。

PROJECT SUMMARY Hepatocellular carcinoma (HCC) accounts for nearly 29,000 deaths annually in the United States alone. However, the molecular mechanisms that drive HCC development remain elusive and current HCC therapies provide negligible clinical benefit. Factors that epigenetically silence an HCC tumor suppressor gene have the potential to promote tumorigenesis and thus may provide novel drug targets for HCC therapies. T o discover such factors, we performed an innovative genome-wide human RNA interference (RNAi) screen to identify factors that mediate epigenetic silencing of the HCC tumor suppressor gene Hedgehog-Interacting Protein (HHIP). HHIP is a negative regulator of Sonic hedgehog (SHH) signaling and loss of HHIP due to epigenetic silencing aberrantly activates SHH signaling, which has been proposed to promote tumor growth in multiple cancers including HCC. One of the factors identified in our screen is CDC-like kinase 1 (CLK1), a dual specificity protein kinase that phosphorylates serine/arginine-rich proteins involved in pre-mRNA splicing. We found that CLK1 transforms cultured immortalized hepatocytes and promotes HCC tumor growth in mouse subcutaneous xenografts, and these effects are dependent upon CLK1 protein kinase activity. Notably, epigenetic silencing of HHIP and CLK1 overexpression occur frequently in HCC patient samples, supporting the clinical relevance of our results. Based on these collective findings, we hypothesize that CLK1 is a driver of HCC and functions by epigenetically silencing the tumor suppressor HHIP. The results of the experiments proposed in this application will establish the role of CLK1 as a driver of HCC, determine the mechanism by which CLK1 promotes tumor growth, and evaluate CLK1 as a drug target for HCC therapy. In Aim 1, we will establish the role of CLK1 in initiation and progression of hepatic tumorigenesis using a series of complementary mouse models that recapitulate characteristic features of HCC. In Aim 2, we will test our hypothesis that CLK1 promotes hepatic tumor growth through epigenetic silencing of HHIP, resulting in aberrant activation of SHH signaling. We will also investigate other mechanisms by which CLK1 may promote tumor growth. In Aim 3, we will evaluate CLK1 as a novel drug target for the development of HCC therapeutics. In preliminary experiments, we have found that inhibition of CLK1 enhances natural killer (NK) cell-mediated eradication of HCC cells. Therefore, we predict that reactivation of HHIP by pharmacological inhibition of CLK1 will: (1) directly inhibit tumor growth by blocking oncogenic SHH signaling, and (2) augment NK cell-mediated eradication of tumor cells. To test these predictions we will determine whether the highly specific CLK1 small molecule inhibitor KH-CB19 can effectively inhibit growth of hepatic tumors and enhance the ability of NK cells to eradicate tumors using a complementary series of immunocompromised and immunocompetent mouse models of HCC. Collectively, the results of the experiments proposed in this application will elucidate a novel druggable pathway that promotes HCC development and evaluate a new approach for treating HCC.