TERT启动子突变及SMYD3在尿路上皮癌中的作用及作用机制的研究

Telomere length and telomerase activity plays an important role in human aging and cancer, TERT promoter point mutations also plays an important role in the process of the activation of telomerase in a wide variety of tumors. TERT promoter can be formed new ETS transcription binding sequence 5'-TTCCGGG-3 'after mutated, by which TERT promoter activity was significantly increased. Our team found that in upper tract urothelial carcinoma, TERT promoter mutation was found in 43% of the renal pelvis carcinoma and 19% ureteral carcinoma and it was positively correlated with upper tract urothelial carcinoma metastasis. SET and MYND domain-containing protein3 (SMYD3) is a histone methyltransferase that targets histone H3-K4 for its di-/tri-methylation. SMYD3 can regulate the expression of hTERT directly, we found that histone methyltransferase SMYD3, an onco-protein, is over-expressed in urothelial cancer tissues and accumulated in nuclear, while the protein is undetectable in normal urothelial tissues, indicating its pro-tumorigenesis function in urothelial cancer. In this study, we aim to delineate the role of TERT promoter mutation in advanced urothelial cancer prognosis and it's clinical value in the early diagnosis; analysis SMYD3 tumor biology and identify its target genes and downstream pathways in urothelial cancer cells. The project promises to improve our understanding of the mechanisms underlying urothelial cancer and pave a novel approach toward target therapies.

端粒长度和端粒酶活性的调节在人类衰老及肿瘤等疾病发生中发挥着重要作用，TERT启动子点突变在多种肿瘤激活端粒酶过程中起着重要作用。TERT启动区突变后可以形成新的ETS转录结合序列5’-TTCCGGG-3’，导致启动子活性明显上调。我们对上尿路尿路上皮癌研究发现：TERT启动子突变在尿路上皮癌中与上尿路尿路上皮癌的转移呈正相关。甲基化转移酶SMYD3在肿瘤发展过程中起到至关重要的作用。SMYD3可以直接上调hTERT的表达，我们近来我们研究结果显示与肿瘤发生发展密切相关的SMYD3在尿路上皮癌中表达异常升高并聚积于细胞核内，提示该酶在尿路上皮癌中的重要作用。本课题拟探讨TERT启动子突变晚期肿瘤预后的关系及其在尿路上皮癌早期诊断中的应用价值；分析SMYD3在尿路上皮癌细胞中的肿瘤生物学作用及作用机制。本研究对于深入了解尿路上皮癌的发病机制并寻找潜在的靶向治疗位点具有重要意义。

端粒酶逆转录酶表达在细胞永生化和肿瘤进展过程中发挥着重要作用，本研究从TERT启动子及FGFR3突变出发讨论其与中国人群膀胱癌新辅助化疗关系，中国人群突变谱及SMYD3在膀胱尿路上皮癌中的作用和作用机制。结果显示中国人群新辅助化疗有效率为53.1%，有效率略低于欧美人群，淋巴结转移，合并不同分化亚型可能是新辅助化疗疗效不佳的危险因素。中国人群TERT启动子及FGFR3两个尿路上皮癌最常见的基因突变率与欧美报道有差异性，特别是FGFR3 突变率非常低（肾盂癌8.8%；输尿管癌2.6%；膀胱癌9.4%），以FGFR3靶点的精准治疗应用可能会在中国人群受到较大限制；中国人群尿路上皮癌基因改变与欧美人群存在差异性，通过WES基因检测显示ERBB2（Her2）在中国人群的突变率明显高于欧美人群，且ERBB2的异常表达率较高，且与膀胱癌患者年龄，分期，病理分级呈相关性，Her2可能是新辅助化疗敏感性的潜在重要预测指标。通过应用敏感性和特异性更高的castPCR法检测尿液C228T突变，检测敏感性与Sanger法相比分别为89%和50%(P < 0.001)，而特异性分别为92%和97% (P = 0.48)，较Sanger测序敏感性及特异性均有较大提高，提高尿液活检在膀胱癌的无创复发早筛的可行性。另外通过多基因联合检测可以进一步提高尿液早筛的敏感性。研究发现组蛋白甲基化酶SMYD3在膀胱癌中表达升高，且与患者病TNM分期，淋巴结转移，病理分级存在相关性，通过全转录组芯片，我们发现SMYD3可能通过ERBB2-PI3K通路调控膀胱癌细胞的生长，我们前面对768膀胱癌ERBB2表达及膀胱癌基因突变检测的结果再次验证了以上结论，ERBB2在中国人群的高表达及高突变率提示ERBB2作为治疗靶点的可行性，对ERBB2介导的膀胱癌发生发展机制对中国人群膀胱癌的治疗有着重要的临床意义。