L1CAM-integrin interaction induces constitutive NF-κB activation in pancreatic adenocarcinoma cells by enhancing IL-1β expression

L1 cell adhesion molecule (L1CAM) overexpression is often associated with bad prognosis in various human carcinomas. Recent studies also suggest a role of L1CAM in pancreatic ductal adenocarcinomas (PDAC). To further address its contribution, we expressed functional domains of L1CAM in PT45-P1 PDAC cells. We found that L1CAM that is full length (L1-FL), but neither the soluble ectodomain (L1ecto) nor the cytoplasmic part (L1cyt), could enhance cell proliferation or tumour growth in mice. Expression of L1-FL resulted in constitutive activation of NF-kappa B, which was abolished by L1CAM knockdown. We showed that the expression of IL-1 beta was selectively upregulated by L1-FL, and increased IL-1 beta levels were instrumental for sustained NF-kappa B activation. IL-1 beta production and NF-kappa B activation were abolished by knockdown of alpha 5-integrin and integrin-linked kinase, but insensitive to depletion of L1CAM cleavage proteinases. Supporting these data, PT45-P1 cells transduced with an L1CAM mutant deficient in integrin binding (L1-RGE) did not support the described L1-FL functions. Our results suggest that membranous L1CAM interacts with RGD-binding integrins, leading to sustained NF-kappa B activation by IL-1 beta production and autocrine/paracrine signalling. The unravelling of this novel mechanism sheds new light on the important role of L1CAM expression in PDAC cells. Oncogene (2010) 29, 4766-4778; doi:10.1038/onc.2010.230; published online 14 June 2010