Neuroblastoma is the most common solid
tumor during early childhood. One of the key features of
neuroblastoma is extensive
tumor-driven angiogenesis due to
hypoxia. However, the mechanism through which
neuroblastoma cells drive angiogenesis is poorly understood. Here we show that the
long noncoding RNA MALAT1 was upregulated in human
neuroblastoma cell lines under hypoxic conditions.
Conditioned media from
neuroblastoma cells transfected with small interfering RNAs (
siRNA) targeting MALAT1, compared with
conditioned media from
neuroblastoma cells transfected with control siRNAs, induced significantly less endothelial cell migration, invasion and vasculature formation. Microarray-based differential gene expression analysis showed that one of the genes most significantly down-regulated following MALAT1 suppression in human
neuroblastoma cells under hypoxic conditions was
fibroblast growth factor 2 (
FGF2). RT-PCR and immunoblot analyses confirmed that MALAT1 suppression reduced
FGF2 expression, and
Enzyme-Linked
Immunosorbent Assays revealed that transfection with MALAT1 siRNAs reduced
FGF2 protein secretion from
neuroblastoma cells. Importantly, addition of recombinant
FGF2 protein to the cell
culture media reversed the effects of MALAT1
siRNA on vasculature formation. Taken together, our data suggest that up-regulation of MALAT1 expression in human
neuroblastoma cells under hypoxic conditions increases
FGF2 expression and promotes vasculature formation, and therefore plays an important role in
tumor-driven angiogenesis.