GRHL3调控EMT和肿瘤干细胞发生而参与肿瘤侵袭及转移分子机制的研究

Many hypotheses have been postulated to explain the intricate nature of the metastatic process, but none of them completely accounted for the actual biological and clinical observations. EMT and cancer stem cells, which are under the control of miRNAs, are mainly involved in the invasion and metastasis of cancer. Skin cancers and breast cancers may be the best disease models for studying cancer invasion and metastasis. Recently, some studies proved that GRHL3, which plays great roles in regulating epithelial cells migration during embryo development。Importantly,other studies indicated that GRHL3 might be involved in cancer invasion and metastasis. In our previous studies, we found that expression level of the GRHL3 would gradually decrease with deeper invasion in the skin cancer; and there was direct correlation between GRHL3 expression and metastasis in breast cancer; EMT and SP cells were occurred in the A431 cells with GRHL3 overexpression; RNA chip showed that molecular markers representing EMT were expressed in the A431 cells with GRHL3 overexpression. Based on these previous studies, we think that EMT and CSC may be occurred under the control of miRNAs mediated by the GRHL3, and then cause invasion and metastasis of cancer. We will try to study GRHL3 functions and its mechanisms for regulating occurrence of EMT and CSC in the skin cancer or breast cancer, and to find new targeted drugs for cancer therapy and to direct cancer patients' personalized treatment.

肿瘤的侵袭、转移是困扰肿瘤治疗的主要因素之一，其分子机制非常复杂，而在微小RNA（miRNA）参与调控的上皮-间质转分化（EMT）和肿瘤干细胞（CSC）的发生是其主要原因之一。GRHL3是胚胎发育阶段参与上皮细胞迁移的重要转录因子，最近研究提示GRHL3可能参与肿瘤的侵袭和转移。皮肤鳞癌以局部侵袭为主要特征；局部侵袭、远处转移是乳腺癌常见表现，二者是研究侵袭和转移较好的疾病模型。我们前期研究发现GRHL3表达水平与皮肤鳞癌的侵袭程度及乳腺癌的侵袭、转移及耐药之间存在相关性；GRHL3的过量表达导致A431细胞中类似CSC的侧群显著增加并伴随发生了EMT的典型特征。故本项目基于"GRHL3参与肿瘤侵袭和转移可能是miRNA参与调控而发生EMT和CSC"这一设想，选用皮肤鳞癌和乳腺癌为疾病模型，以探讨GRHL3参与调控肿瘤侵袭和转移的分子机制，寻求抗肿瘤的新型药物靶点并指导临床个体化治疗。

GRHL3是胚胎发育阶段参与上皮细胞迁移的重要转录因子，我们研究发现皮肤鳞癌、乳腺癌等组织标本中GHRL3的表达与肿瘤细胞的局部侵袭和远处转移存在正相关。提示GRHL3可参与肿瘤的侵袭和迁移。细胞水平研究其作用机制主要通过结合E-cadherin基因上游的启动子特定序列抑制其表达。细胞形态变化、细胞生物学行为的改变以及表达芯片、Chip-seq等结果证实这种抑制作用可能通过诱发EMT所致。同时GRHL3还可以通过抑制SNX16基因表达而促进肿瘤细胞的迁移和侵袭。尽管GRH家族成员中GRHL1、GRHL2在肿瘤细胞中作用表现为抑制迁移和侵袭，但我们的研究结果初步揭示了GRHL3在影响肿瘤细胞迁移和侵袭中作用及其分子机制与其家族成员GRHL1、GRHL2等明显不同，为后续研究他们之间的相互关系具有重要的理论意义。同时我们对GRHL3的上游调控分子CtBP在参与调控肿瘤细胞的氨基酸代谢和糖代谢方面进行了相关探讨，发现肿瘤细胞中糖酵解与谷氨酰胺分解代谢调控依赖CtBP-SIRT4-GDH（谷氨酸脱氢酶）相互调控。在高葡萄糖环境中，CtBP可以抑制SIRT4表达；而低葡萄糖环境通过抑制CtBP的二聚化而降低GDH的活性，进而抑制谷氨酸的分解。此外，我们还对GRHL3的协作分子LMO4在银屑病的发生发展中机制开展了相应研究。结果发现GRHL3的协作分子LMO4在银屑病皮损部位表达水平明显增加，细胞水平和动物模型的研究证实抑制LMO4的表达可以明显抑制角质形成细胞的增殖和分化，从而为抑制银屑病患者的角质形成细胞的过度增殖和异常分化进而为临床上减少银屑病患者皮屑产生提供重要的理论意义和重要应用价值。