German Cancer Research CenterIm Neuenheimer Feld 280, Heidelberg, Germany.
Carcinogenesis. 2012 Oct;33(10):1919-29. doi: 10.1093/carcin/bgs220. Epub 2012 Jul 4.
Expression of L1 cell adhesion molecule (L1CAM) is associated with poor prognosis in a variety of human carcinomas including breast, ovarian and pancreatic ductal adenocarcinoma (PDAC). Recently we reported that L1CAM induces sustained nuclear factor kappa B (NF-κB) activation by augmenting the autocrine production of interleukin 1 beta (IL-1β), a process dependent on interaction of L1CAM with integrins. In the present study, we demonstrate that transforming growth factor β1 (TGF-β1) treatment of breast carcinoma (MDA-MB231) and PDAC (BxPc3) cell lines induces an EMT (epithelial to mesenchymal transition)-like phenotype and leads to the expression of L1CAM. In MDA-MB231 cells, up-regulation of L1CAM augmented expression of IL-1β and NF-κB activation, which was reversed by depletion of L1CAM, L1CAM-binding membrane cytoskeleton linker protein ezrin, β1-integrin or focal adhesion kinase (FAK). Over-expression of L1CAM not only induced NF-κB activation but also mediated the phosphorylation of FAK and Src. Phosphorylation was not induced in cells expressing a mutant form of L1CAM (L1-RGE) devoid of the integrin-binding site. FAK- and Src-phosphorylation were inhibited by knock-down of various components of the integrin signalling pathway such as β1- and α5-integrins, integrin-linked kinase (ILK), FAK and the phosphoinositide 3-kinase (PI3K) subunit p110β. In summary, these results reveal that during EMT, L1CAM promotes IL-1β expression through a process dependent on integrin signalling and supports a motile and invasive tumour cell phenotype. We also identify important novel downstream effector molecules of the L1CAM-integrin signalling crosstalk that help to understand the molecular mechanisms underlying L1CAM-promoted tumour progression.
L1 细胞黏附分子（L1CAM）的表达与多种人类癌包括乳腺癌、卵巢癌和胰腺导管腺癌（PDAC）的不良预后相关。最近我们报道 L1CAM 通过增强白细胞介素 1β（IL-1β）的自分泌产生来诱导持续的核因子 κB（NF-κB）激活，这个过程依赖于 L1CAM 与整合素的相互作用。在本研究中，我们证明转化生长因子β1（TGF-β1）处理乳腺癌（MDA-MB231）和 PDAC（BxPc3）细胞系诱导 EMT（上皮间质转化）样表型，并导致 L1CAM 的表达。在 MDA-MB231 细胞中，L1CAM 的上调增强了 IL-1β的表达和 NF-κB 的激活，而 L1CAM 的耗竭、L1CAM 结合膜细胞骨架连接蛋白 ezrin、β1-整合素或粘着斑激酶（FAK）则逆转了这一过程。L1CAM 的过表达不仅诱导了 NF-κB 的激活，还介导了 FAK 和Src 的磷酸化。缺乏整合素结合位点的 L1CAM 突变体（L1-RGE）的表达并不诱导磷酸化。FAK 和Src 的磷酸化被各种整合素信号通路成分的敲低抑制，如β1 和α5 整合素、整合素连接激酶（ILK）、FAK 和磷酸肌醇 3-激酶（PI3K）亚基 p110β。总之，这些结果表明，在 EMT 过程中，L1CAM 通过依赖于整合素信号的过程促进 IL-1β 的表达，并支持运动和侵袭性肿瘤细胞表型。我们还确定了 L1CAM-整合素信号串扰的重要新下游效应分子，有助于理解 L1CAM 促进肿瘤进展的分子机制。
