炎症微环境通过下调PP2Ac抑制胰腺癌细胞Par/aPKC极性复合体形成并诱导EMT的机制研究

Pancreatic cancer has the proclivity of early metastasis. Inflammatory tumor microenvironment correlates with the development and progression of pancreatic cancer. Inflammation promotes metastasis by inducing epithelial-mesenchymal transition (EMT), in which epithelial cells lose polarity, break down cell-cell and cell-extracellular matrix connections, and acquire the metastatic capacity. With the support of our previous NSFC grant, we have demonstrated that inflammation promoted metastasis through downregulation of PP2Ac (protein phosphatase 2A catalytic subunit). Inhibition of PP2Ac disrupted cell polarity and induced EMT. Par/aPKC complex is a key regulator of cell polarity. Because the function of PP2A is highly conserved in Drosophila, in which PP2A is an essential regulator of Par/aPKC complex; we propose that inflammatory tumor microenvironment induces EMT and metastasis in pancreatic cancer cells by suppressing PP2Ac, resulting the inhibition of the Par/aPKC complex formation. By using several well-established animal models, various contemporary molecular biology techniques, and human pancreatic cancer specimens, we will investigate the critical role and function of the Par/aPKC complex in the progression of pancreatic cancer in vitro and in vivo. We will also delineate the signal pathway underlying the PP2Ac-Par/aPKC axis in inflammation-mediated EMT. Our study will not only establish a new paradigm that significantly affects our views on how chronic inflammation leads to the disruption of cell polarity in EMT and metastasis, but will also lay groundwork for developing new therapeutic strategies against the deadly pancreatic cancer.

胰腺癌易转移。炎症是胰腺癌高危因素，可诱导癌细胞发生EMT（上皮-间质转化），促进转移。细胞极性丧失是EMT的特征之一。课题组在前一NSCF资助下研究发现：①炎症通过下调PP2Ac（蛋白磷酸酶2A催化亚基），促进胰腺癌细胞转移；②抑制PP2Ac，可削弱细胞极性并诱导EMT。Par/aPKC复合体是调控细胞极性的关键，最近发现PP2A是其调控因子。我们推测炎症微环境抑制胰腺癌细胞PP2Ac后，很可能通过影响Par/aPKC复合体的形成而削弱细胞极性，进而诱导EMT并促进转移。依靠前期建立的多种动物模型，结合分子生物学手段和临床样本检测，本项目将研究：①Par/aPKC复合体对胰腺癌演进过程的影响；②炎症/PP2Ac信号通路，对胰腺癌细胞EMT和转移的调控作用，以及这种调控是否由Par/aPKC复合体依赖性机制介导。本研究有助于阐明炎症微环境促胰腺癌转移的分子机制，有望为胰腺癌治疗找到新靶点。

炎症是胰腺癌高危因素，可诱导癌细胞发生EMT（上皮—间质转化），促进转移。细胞极性丧失是EMT 的特征之一。本研究发现：①.体外炎症因子刺激可促进胰腺癌生长转移；通过建立具有炎症基础的胰腺原位移植瘤模型，证实炎症微环境能够促进移植瘤的生长转移；体外研究证实炎症刺激通过激活NF-κB信号通路抑制PP2Ac表达；体外研究证实炎症刺激通过NF-κB/PP2Ac通路依赖性机制，促进胰腺癌细胞侵袭转移，促进胰腺癌细胞发生EMT；采用免疫共沉淀证实过表达PP2Ac促进Par/aPKC极性复合体形成。②.为了证明炎症微环境对肿瘤演进的影响的普适性，我们进一步建立了具有炎症基础的肺癌移植瘤模型，并证实炎症微环境中的肿瘤相关巨噬细胞（TAMs）能够促进肺癌的生长转移；TAMs通过抑制PP2Ac表达，促进肺癌细胞生长转移；TAMs通过NF-κB通路依赖性机制促进肺癌细胞生长转移；通过生物信息学筛选出CXCL1、COL6A1可能与TAMs的促癌作用有关；通过克隆CXCL1、COL6A1启动子证实TAMs通过NF-κB通路依赖性机制调控CXCL1、COL6A1转录；CXCL1促进肿瘤血管生成，促进移植瘤生长；COL6A1促进肿瘤细胞的生长转移，并在体内促进移植瘤生长。③. PP2A抑制剂Cantharidin（斑蝥素）被认为具有抗肿瘤作用，并应用于临床。我们的前期研究显示Cantharidin对体外培养的胰腺癌细胞的生长转移具有显著的抑制作用，但其抗肿瘤作用尚未在体内进行验证。本研究中，我们建立了胰腺癌移植瘤模型，并在体内水平研究了Cantharidin对胰腺肿瘤生长的影响，意外发现Cantharidin显著促进肿瘤血管生成，并促进移植瘤的生长；Cantharidin或其衍生物联合抗血管生成药物，可发挥协同抗肿瘤作用。