二氢乳清酸脱氢酶DHODH调控β-catenin表达并增强食管鳞癌细胞干性的分子机制

Esophageal squamous cell carcinoma (ESCC) is one of the most common malignancies with high mortality. Our preliminary study found that deregulated pyrimidine metabolism significantly occurred in the early stages of ESCC, implying the pro-tumorigenesis roles of pyrimidine metabolism enzymes. Dihydroorotate dehydrogenase (DHODH) is the key regulatory enzyme on pyrimidine synthesis. Further investigation indicated that the expression level of DHODH was significantly higher in ESCC tissues compared with that in adjacent non-cancer tissues. Moreover, high expression of DHODH was closely associated with tumor differentiation status and poor prognosis of ESCC. In addition, we observed that DHODH could promote proliferation and enhance self-renewal ability of ESCC cells, which were related to the interacting and activating of β-catenin, followed by the up-regulation of stem associated factors, such as Nanog and E2F3. However, the precise mechanism remains elusive. The further experiments would be performed to investigate the expression correlation between DHODH and β-catenin and explore the DHODH mediated β-catenin stabilization in vitro and in vivo. This study may illustrate the pivotal roles of DHODH in pyrimidine metabolism and cell stemness, which could provide a novel target for the diagnosis and treatment of ESCC.

食管鳞状细胞癌（ESCC）是我国高发病率和高致死率的恶性肿瘤，课题组前期研究提示嘧啶代谢通路可能在ESCC早期发展中发挥重要作用。二氢乳清酸脱氢酶（DHODH）是嘧啶代谢中的限速酶，在ESCC组织中表达量显著上升，与ESCC患者的临床病理分级和不良预后有关。初步发现DHODH促进细胞增殖、提高细胞干性；且与β-catenin相互作用，上调其表达，提示DHODH通过调控β-catenin转录激活干性相关因子如Nanog,E2F3等，介导ESCC细胞干性提高，但具体机制不明。我们拟进一步分析ESCC组织中DHODH与β-catenin表达的相关性；重点关注DHODH对β-catenin活性及稳定性的调控，及对ESCC细胞成瘤性的影响。本研究围绕DHODH调控嘧啶代谢和细胞干性的枢纽作用，研究ESCC细胞嘧啶代谢产物和干性表型，有助于阐明代谢酶异常导致肿瘤恶性的机制，为ESCC的防治提供新思路。

研究背景: 食管鳞状细胞癌是我国高发病率和高致死率的恶性肿瘤，课题组前期研究提示嘧啶代谢通路可能在ESCC早期发展中发挥重要作用。二氢乳清酸脱氢酶（DHODH）是嘧啶代谢中的限速酶，但其功能在食管鳞癌中未知。.研究内容：统计临床样本中DHODH表达，分析DHODH与食管鳞癌分期，分型等临床病理参数以及预后的相关性；在食管鳞癌细胞系中分别过表达和敲低DHODH，研究其对细胞增殖，体内成瘤的影响；通过RNA-测序，免疫共沉淀，生物膜干涉（BLI）等实验研究DHODH影响下游的重要基因和促癌的潜在机制。.结果：1.DHODH高表达与食管鳞癌恶性程度正相关, 提示不良预后；过表达DHODH促进细胞增殖和体内成瘤，敲低结果反之；RNA-测序提示DHODH调控β-catenin通路，敲低DHODH抑制下游促癌基因的表达；免疫共沉淀，BLI实验等提示DHODH直接结合β-catenin，抑制GSK3β介导的降解途径，稳定β-catenin并促进核转移，最终促进下游癌基因的转录，进而推动食管鳞癌发展。.意义：本研究部分揭示了食管鳞癌发展的可能机制，提供了食管鳞癌新的潜在生物标志物，并为食管鳞癌的精准诊疗提供新的治疗靶点。