酪氨酸代谢酶HPD在肺癌发生发展中的作用及机制研究

Amino acids catabolism dysregulation plays key role in tumorigenesis and malignant development. Characterization of novel metabolism enzymes involved in tumor malignancy will help to illustrate the molecular mechanism of metabolism dysregulation in tumor and develop potential drug target. 4-hydroxyphenylpyruvate dioxygenase(HPD) is the key metabolism enzyme in tyrosine catabolism. Previous study suggest that HPD is specifically expressed in liver and kidney, deletion of HPD function or activity led to tyrosinemia. Our previous study suggested that HPD is upregulated in lung cancer cell lines and cancer tissue of lung cancer patients. Knockdown of HPD in A549 cells led to decreased cell proliferation and migration and enhanced cell apoptosis induced by serum withdrawal and Gefitinib treatment.These results suggest that HPD might play key role in tumorigenesis and development of lung cancer. The purpose of this study is to clarify the role of HPD in the tumorigenesis and development of lung cancer using various lung cancer cell lines and mice models. The molecular mechanism of HPD was investigated by molecular biology technology such as genetic expression microarray, Western blotting and real-time PCR analysis. Correlation between the expression level of HPD and prognosis in lung cancer is analyzed by clinical data. It is promising that this study may identify a novel metabolism enzyme involved in lung cancer and a potential biomarker in diagnosis, prognosis of lung cancer. It may also provide a potential taget of lung cancer therapy in future.

氨基酸代谢异常在肿瘤发生发展中发挥重要作用，发掘新的调控肿瘤恶变的关键代谢酶，有助于揭示肿瘤代谢异常机制，开发潜在药物靶标。4-羟苯丙酮酸二加氧酶HPD是酪氨酸代谢中的关键酶，特异表达于肝脏与肾脏，HPD功能缺失可引起酪氨酸血症。我们的研究表明HPD在肺癌细胞株及肺癌病人中异常高表达，敲低HPD可抑制肺癌细胞恶性表型，提示HPD很可能调控肺癌发生与发展。本项目拟利用肺癌细胞株，在细胞水平明确HPD对肺癌恶性表型的影响；利用多种动物模型，从整体水平明确HPD对肺癌细胞生长、转移的作用；利用特异抑制剂及酶活性突变体，明确HPD代谢酶活性在调控肺癌恶性表型中的作用；在大样本临床肺癌病人组织、血清中检测HPD表达水平，结合临床资料，揭示HPD表达水平与肺癌发生转移、生存期等的关联。本研究的实施可望发现一种新的调控肺癌发生发展的代谢酶，为肺癌诊断、预后及靶向治疗提供潜在分子标志物和候选靶标。

HPD是酪氨酸代谢途径的一个关键酶，在肾脏和肝脏中高表达，其它组织中低表达或不表达。本研究发现HPD在肺癌病人组织、肺癌病人血清及多种肺癌细胞系中异常高表达，并且HPD过表达可以促进肺癌细胞的体内、外迁移能力、降低肺癌细胞对化疗药物的敏感性。反之，敲低HPD可抑制肺癌细胞的迁移能力，增强肺癌细胞对化疗药物的敏感性。进一步的机制探讨发现HPD发挥调控肺癌恶性表型的作用依赖于其代谢酶活性。酪氨酸代谢通路中的代谢产物也参与了肺癌的迁移与药物敏感性调控。此外，我们研究了HPD在肺癌中异常高表达的调控机制，结果显示转录因子HNF4α可结合HPD的启动子区特定位点，增强其启动子活性与内源性表达水平，并且与HPD在肺癌组织中呈现高的相关性，提示HNF4α是调控HPD在肺癌中异常高表达的关键因子。本研究一方面首次揭示了酪氨酸代谢酶HPD调控肺癌表型的新功能，为肺癌的诊断提供了潜在的分子标志物，另一方面提出在肺癌中可能存在酪氨酸代谢通路的重塑，揭示了酪氨酸代谢过程在肺癌发生、发展的重要作用。