Abstract
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.
Highlights
Neuroblastoma, originating from precursor neuroblast cells in the sympathetic nervous system, is the most common extracranial malignancy in children, and accounts for 15% of all childhood cancer deaths [1].One of the key features of human neuroblastoma tissues is extensive tumor-driven angiogenesis [2].Angiogenesis is a pre-requisite for tumor progression and metastasis [3]
We have previously shown that MALAT1 gene expression is up-regulated by the histone demethylase JMJD1A in neuroblastoma cells, and that MALAT1 induces neuroblastoma cell migration and invasion [16]
Since MALAT1 is well-known to be over-expressed in metastatic, compared with primary, human tumor tissues [11, 12, 17], and hypoxia is known to induce tumour cell metastasis, we examined whether hypoxia up-regulated MALAT1 gene expression in human neuroblastoma cell lines
Summary
Neuroblastoma, originating from precursor neuroblast cells in the sympathetic nervous system, is the most common extracranial malignancy in children, and accounts for 15% of all childhood cancer deaths [1].One of the key features of human neuroblastoma tissues is extensive tumor-driven angiogenesis [2].Angiogenesis is a pre-requisite for tumor progression and metastasis [3]. When placed in a state of prolonged or severe reduction of tissue oxygen tension, or hypoxia, cancer cells undergo adaptive changes that allow www.impactjournals.com/oncotarget them to up-regulate the expression of pro-angiogenic genes, leading to tumor-driven angiogenesis, tumor cell survival, proliferation and metastasis [4]. Long noncoding RNAs (lncRNAs) are transcripts more than 200 nucleotides in length without a functional open reading frame. According to their genetic location in relation to neighbouring protein-coding genes, lncRNAs can be divided into sense, antisense, bidirectional, intronic and intergenic subtypes [6, 7]. The lncRNA HOTAIR regulates the expression of genes critical for tumor cell invasion, and plays a critical role in breast cancer cell invasion and metastasis [10]
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