Background: Neuroblastomas (NBL) are tumors with a high rate of metastases (50% of patients). In general, in NBL MYCN amplification (NMA) is the most important prognostic factor. However NMA is infrequent and 70% of NBL are non-NMA tumors and not much is known about the driving oncogenic event. Recently, we identified among 17 NBL cell lines a group of non-NMA NBL cell lines with a distinct gene expression profile (HU133plus2.0 arrays, Affymetrix) and high expression of the AXL gene. AXL is a tyrosine kinase receptor, associated with the metastatic process of several cancers. We hypothesized that AXL contributes to metastsizing potential in non-NMA neuroblastomas and tested if AXL silencing diminishes malignant properties of high AXL expressing cell lines. Results: High expression of AXL was detected in G-IM-EN, SK-N-AS and two subclonal cell lines SH-EP-2 and SH-EP-21N. AXL was silenced (lentiviral AXL shRNA expression plasmids, pLKO.1_shAXL, Sigma-Aldrich) in GI-M-EN and SH-EP-2 with an infection efficiency of >90% and 80-85% AXL-mRNA knockdown. We examined the silencing effect on migration and invasion. A significant reduction of migration (74.7%) and invasion (99.8%) was achieved in GI-M-EN. In the intermediate AXL expressing expressing cell line SH-EP-2 migration reduction was less (41.9%). Furthermore, GI-M-EN and SH-EP-2 were compared for cytoskeletal, morphological changes after silencing. Cells became rounded with small lamellipodia and filopodia and F-actin fluorescent staining showed induction of F-actin positive stress-fibers (17.3%), both most prominent in high AXL expressing GI-M-EN. In SH-EP-2 the number of cells with stress fibers was increased (9.9%). Expression of, matrix metalloproteinase 9 frequent down-stream target of EMT-like processes, was not changed upon silencing of AXL. Also, we observed no effects on cell proliferation, apoptosis or downstream pathways (PI3K-AKT, MAPK-ERK pathway). Conclusion: The AXL gene is highly expressed in a subset of non-NMA NBL cell lines and seems involved in migratory and invasion properties. AXL is a possible mediator of NBL metastasis.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2490. doi:1538-7445.AM2012-2490