L1 Cell Adhesion Molecule Promotes Migration and Invasion via JNK Activation in Extrahepatic Cholangiocarcinoma Cells with Activating KRAS Mutation

Abstract

Extrahepatic cholangiocarcinoma (ECC), a malignant tumor of biliary origin, has a poor prognosis with limited treatment options. The KRAS oncogene is the most commonly mutated gene in ECC and one of the factors that predicts a poor prognosis and low survival rate. L1 cell adhesion molecule (L1CAM) is expressed in ECC cells and acts as an independent poor prognostic factor in predicting patient survival. In this study we investigate the functional significance of L1CAM in ECC cells with activating KRAS mutation. We selected an ECC cell line, EGI-1, with activating KRAS mutation, and then confirmed its expression of L1CAM by RT-PCR, western blot analysis, and flow cytometry. The suppression of L1CAM expression (using a specific lentivirus-delivered shRNA) significantly decreased the migratory and invasive properties of EGI-1 cells, without altering their proliferation or survival. Analyses of signaling effectors in L1CAM-depleted and control EGI-1 cells indicated that L1CAM suppression decreased the levels of both phosphorylated MKK4 and total MKK4, together with c-Jun N-terminal kinase (JNK) phosphorylation. Further, exposure to a JNK inhibitor (SP600125) decreased migration and invasion of EGI-1 cells. These results suggest that L1CAM promotes cellular migration and invasion via the induction of MKK4 expression, leading to JNK activation. Our study is the first to demonstrate a functional role for L1CAM in ECC carrying the activating KRAS mutation. Given that KRAS is the most commonly mutated oncogene in ECC, L1CAM may serve as an attractive therapeutic target for ECC cells with activating KRAS mutation.

L1 Cell Adhesion Molecule in Cancer, a Systematic Review on Domain-Specific Functions

“…In a total of 19 studies investigated the impact of full-length L1CAM (L1CAM-FL) on tumor suppression with strategies that did not specifically address domain-specific functions of L1CAM [34,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61]. A complete overview of the main study strategies and findings is outlined in Table S1 and a summary of results can be found in Figure 3.…”

“…Besides promoting proliferation, ERK-dependent gene expression downstream of L1CAM is reported for ESCC [45] and melanoma [51], resulting in gene expression involved in migration and invasion. In contrast to these publications, several other studies that investigated the role of ERK were unable to demonstrate its activation, but reported activation of JNK, p38 MAPK and/or Akt/PI3K, in respectively, gastic cancer [49], extrahepatic cholangiacarcinoma [46], retinoblastoma [56] or gall bladder cancer [48]. Activation of these pathways may also occur in parallel with ERK activation, for instance in ovarian carcinoma [55].…”

Molecular Mechanisms Driving Cholangiocarcinoma Invasiveness: An Overview

“…Indeed, prolonged exposure of CCA cells to increasing concentrations of gemcitabine led to a substantial increase in migration and invasion, an effect coupled with the aberrant activation of the FAK/MAPK/NF-κB axis, which is eventually responsible for enhanced MMP-9 production 84 . Similarly, long-term exposure of CCA cell lines or xenografts to cisplatin induced the overactivation of EGFR, and the up-regulation of L1 cell adhesion molecule (L1CAM) 85 , a transmembrane glycoprotein supporting the migratory and invasive potential of neoplastic cholangiocytes 86 . Unfortunately, the modulatory effects of genotoxic therapies further complicate the characterization of the wide and heterogeneous range of molecular mechanisms through which CCA cells gradually adopt an invasive phenotype.…”