DACH2调控Smad4/R-Smad通路介导上皮间质转化促进膀胱癌的侵袭转移

Lymph node metastasis is the primary cause of mortality from bladder cancer. In our previous studies, using gene expression profile chip we showed that both DACH2 protein and mRNA expression were greatly increased in bladder cancer patients with lymph node metastasis. Patients with primary bladder cancer that did not express DACH2 had a longer metastasis-free survival and overall survival than did those with tumors expressing DACH2 [BBRC, 2015]. However, the molecular mechanisms of DACH2 initiating bladder cancer metastasis still remain obscure. Our recent investigations also showed: (1) DACH2 could contribute to bladder cancer cell metastasis via promoting epithelial-mesenchymal transition (EMT). (2) There is a positive correlation between relative DACH2 expression and its corresponding Smad4 expression in bladder cancer cells. (3) DACH2 could directly bind Smad4 protein. Herein, based on these findings and the close correlation between Smad4 and EMT, we speculate and present the novel mechanisms underlying DACH2-inducing lymph node metastasis in bladder cancer: DACH2 overexpression could alter the activity of EMT-related gene expression via Smad4/R-Smad signal pathway, thus contributes to EMT, the formation of invasive pseudopod, and degrading extracellular matrix. The present study would elucidate the mechanisms of EMT-related gene expression alteration induced by DACH2 overexpression in bladder cancer. Our results may provide novel and imperative molecular targets for the intervention of bladder cancer metastasis.

淋巴转移是膀胱癌致死的重要原因。我们前期采用基因表达谱芯片筛选膀胱癌转移相关基因，发现DACH2在盆腔淋巴结阳性膀胱癌组织样本中转录和蛋白表达水平均明显上调，DACH2阳性膀胱癌术后无转移生存率和总体存活率明显低于DACH2阴性者[BBRC,2015]，但DACH2促进膀胱癌侵袭转移的机制尚不明确。结合近期预实验结果: DACH2可通过促进上皮-间质转化(EMT)增强膀胱癌细胞转移能力；癌细胞中DACH2与Smad4表达成正相关；DACH2可与Smad4发生直接结合。同时，鉴于Smad4与EMT过程密切关联，我们提出DACH2促进膀胱癌淋巴转移新机制：DACH2可通过Smad4/R-Smad通路，改变EMT相关基因转录活性，促进膀胱癌细胞EMT、侵袭性伪足形成及降解细胞外基质。本研究力图解析DACH2过表达介导EMT促进膀胱癌侵袭转移的机理，有望为临床抑制膀胱癌转移提供重要的分子干预靶点。

转移是膀胱癌致死的重要原因，但其机制不明。我们前期采用基因表达谱芯片筛选膀胱癌转移相关基因DACH2，本项目发现过表达的DACH2可通过Smad4/R-Smad途径，改变上皮间质转化（EMT）相关基因转录活性，进而促进膀胱癌细胞的EMT、侵袭性伪足形成及降解细胞外基质，从而促进膀胱癌进展及转移；应用慢病毒感染上调膀胱癌细胞系DACH2的表达，观察膀胱癌细胞侵袭、迁移、克隆形成能力、侵袭性伪足形成、降解胞外基质的能力的改变；进一步在在体外实验水平，证实膀胱癌中DACH2异常表达促进Smad4高表达，从而导致膀胱癌细胞EMT和侵袭转移；通过建立免疫缺陷小鼠（NOD/SCID）原位成瘤模型、皮下成瘤+慢病毒瘤内注射模型及尾静脉注射转移模型，观察上调/下调DACH2基因表达膀胱癌细胞对肿瘤大小、淋巴结转移、肝肺转移情况影响，在动物实验水平证实DACH2可促进膀胱癌细胞动物体内转移能力；在临床水平，评价了膀胱组织、尿液DACH2在膀胱癌淋巴转移和预后预测中的意义，发现DACH2表达在判断膀胱尿路上皮癌预后方面具有重要价值，其可作为靶向治疗的候选新靶点，指导膀胱癌的临床诊疗。