Mesenchymal change and drug resistance in neuroblastoma

Background: Metastatic initiation has many phenotypic similarities to epithelial-tomesenchymal transition, including loss of cell-cell adhesion, increased invasiveness, and increased cell mobility. We have previously demonstrated that drug resistance is associated with a metastatic phenotype in neuroblastoma (NB). The purpose of this project was to determine if the development of doxorubicin resistance is associated with characteristics of mesenchymal change in human NB cells. Materials and methods: Total RNA was isolated from wild type (WT) and doxorubicinresistant (DoxR) human NB cell lines (SK-N-SH and SK-N-BE(2)C) and analyzed using the Illumina Human HT-12 version 4 Expression BeadChip. Differentially expressed genes (DEGs) were identified. Volcano plots and heat maps were generated. Genes of interest with a fold change in expression >1.5 and an adjusted P < 0.1 were analyzed. Immunofluorescence (IF) and Western blot analysis confirmed microarray results of interest. Matrigel invasion assay and migration wounding assays were performed. Results: Volcano plots and heat maps visually demonstrated a similar pattern of DEGs in the SK-N-SH and SK-N-BE(2)C DoxR cell lines relative to their parental WT lines. Venn diagramming revealed 1594 DEGs common to both DoxR cell lines relative to their parental cell lines. Network analysis pointed to several significantly upregulated epithelial-tomesenchymal transition pathways, through TGF-beta pathways via RhoA, PI3K, and ILK and via SMADs, as well as via notch signaling pathways. DoxR cell lines displayed a more invasive phenotype than respective WT cell lines. Conclusions: Human SK-N-SH and SK-N-BE(2)C NB cells display characteristics of mesenchymal change via multiple pathways in the transition to a drug-resistant state.