Expression array of peripheral neuro-ectodermal cell lines

To study differentially expressed genes in neuro-ectodermal cell lines MYCN amplification (NMA) is the most important prognostic factor in neuroblastoma (NBL) patients, however 70% of advanced stage NBL are non-NMA and lack known driving oncogenic events. Gene expression profiles (HU133plus2.0 arrays, Affymetrix) of 17 NBL and 5 peripheral neuro-ectodermal cell lines were used to identify potential subgroups of NBL cell lines with a distinct gene signature. One group of non-NMA NBL cell lines was identified with a distinct gene expression profile and characterized by high expression of AXL. AXL is a tyrosine kinase receptor which plays a role in the metastatic process of cancer. We hypothesized that AXL contributes to the metastasizing potential of non-NMA NBL and tested if AXL silencing diminishes malignant properties of high AXL expressing cell lines. AXL was silenced in two non-NMA NBL cell lines by using a lentiviral shRNA construct that was able to transduce these cell lines with >90% infection efficiency. AXL mRNA expression level was efficiently knocked-down resulting in a severe decrease of migration of AXL positive cell lines GI-M-EN and SH-EP-2, and decreased invasion of GI-M-EN. Morphologically, AXL knockdown induced more rounded cells with a loss of contact. Intracellularly, we observed induction of stress fibers (immunofluorescence F-actin) in GI-M-EN. These changes in cytoskelet were associated with decreased migration. No effects were observed for cell proliferation, apoptosis or downstream pathways. In conclusion, AXL is identified as a possible mediator of NBL metastasis. Arrays were performed with 5 different PNET cell lines, which were used as controls for 17 NBL cell lines (GSE22771)