甲羟戊酸途径对膀胱癌作用及其机制的研究

In recent years, many studies have been focused on the correlation between the metabolism disorder and the development of cancer, however, the exact mechanisms in bladder cancer remains unclear. Our previous study suggested that compared with normal bladder tissues, the pathways of lipid metabolism were disturbed in bladder cancer. We also found that simvastatin, a 3-hydroxy-3-methyl glutaryl coenzyme A (HMG-CoA) reductase inhibitor, could reduce bladder cancer cell proliferation and induce cell cycle arrest at G0/G1 phase. As one of the most important lipid metabolism pathways, mevalonate pathway could have effect on lipid rafts mediated internalization, than disturb the downstream signaling pathways. Furthermore, 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), the key enzyme of mevalonate pathway and the target of simvastatin, was overexpressed in bladder cancer and negatively correlated with survival of patients. Collectively, we assume that HMGCR may play an important role in the development of bladder cancer. In this study, clinical samples will been collected to detect the altered metabolites of mevalonate pathway, which would be the potential metabolic markers for diagnosis and treatment of bladder cancer. Meanwhile, by using in vivo and in vitro experiments we would like to investigate the underlying mechanisms of the effect of HMGCR on bladder cancer, to provide the theoretical basis for combinated statins with other drugs for bladder cancer treatment.

近年来，脂代谢紊乱与肿瘤的相关研究越来越多，但是其在膀胱癌发生发展中的作用机制尚不明确。课题组前期结果发现在膀胱癌中脂质代谢通路异常激活。同时，应用降脂药物辛伐他汀可以抑制膀胱癌细胞生长并引起周期阻滞。甲羟戊酸途径作为重要的脂代谢途径，其代谢产物的异常可以导致脂质阀内化，进而影响下游信号通路。HMGCR作为其核心限速酶，也是辛伐他汀降脂作用的靶点。课题组发现HMGCR在膀胱癌组织中高表达并与患者生存率呈负相关，敲减HMGCR可以导致其下游PI3K/AKT和MAPK等重要信号通路的改变，提示其可能作为甲羟戊酸代谢途径的核心因子影响膀胱癌的发生发展。本课题拟通过临床组织，血液和尿液样本检测甲羟戊酸途径中代谢产物含量变化，为早期诊治膀胱癌提供潜在代谢标志物；通过体内外实验探究HMGCR对膀胱癌生物行为学影响及其相应机制，为他汀类药物和靶向药物联用治疗膀胱癌提供理论基础。

探究膀胱癌发生发展的机制是解决目前膀胱癌诊疗困境的最可能方法。课题组前期针对膀胱癌的系列研究揭示了以甲羟戊酸途径为重点的脂质代谢紊乱可能是膀胱癌发生发展的关键因素之一。本项目利用膀胱癌患者肿瘤组织及癌旁组织样本、尿液样本、细胞及动物模型，采用生物信息学、细胞生物学、分子生物学等技术方法，进一步明确了甲羟戊酸途径在膀胱癌发生发展中的作用及分子机制。主要发现有（1）与癌旁组织相比，膀胱癌组织中HMGCR高表达，并与患者预后呈负相关，且膀胱癌患者尿液中甲羟戊酸途径中间产物FPP和GGPP的含量相对更高；（2）体外实验证实HMGCR敲减后，膀胱癌细胞的增殖和迁移能力明显受到抑制，并且裸鼠荷瘤实验也证实，敲低HMGCR后，成瘤能力降低；（3）HMGCR可以通过影响EMT和AKT/mTOR信号通路，进而参与膀胱癌细胞增殖和转移能力的调控；（4）甲羟戊酸途径中间代谢产物GGPP（而非FPP）在膀胱癌细胞迁移能力的调控中起重要作用；（5）联合应用AKT特异性抑制剂MK2206后能够使HMGCR敲低的膀胱癌细胞的增殖及转移能力进一步受到抑制，此外，应用辛伐他汀和EGFR/ERBB2抑制剂联合给药对膀胱癌细胞增殖的抑制作用更为显著。通过本项目的研究，进一步揭示了甲羟戊酸途径相关代谢产物及关键酶在膀胱癌发生发展中的重要作用及机制，有望为膀胱癌的早期诊断提供潜在的代谢标志物，为他汀类药物和靶向药物联合治疗膀胱癌提供实验依据。