Eradication of neuroblastoma by suppressing the expression of a single noncoding RNA [MEETING ABSTRACT]

N-Myc gene amplification occurs in one quarter of human neuroblastoma tissues, and is a marker for poor patient prognosis. We performed RNA sequencing experiments, and identified 5 transcripts, including RP1NB1, which were most considerably differentially expressed between N-Myc gene amplified and nonamplified human neuroblastoma cell lines. Affymetrix microarray studies revealed that DEPD was one of the few genes considerably downregulated in neuroblastoma cells after RP1NB1 depletion. Chromatin immunoprecipitation assays showed that knocking down RP1NB1 expression reduced histone H3 lysine 4 trimethylation, a marker for active gene transcription, at the DEPD gene promoter. Luciferase assays demonstrated that knocking down RP1NB1 decreased DEPD gene promoter activity. Depletion of RP1NB1 or DEPD with two independent siRNAs or shRNAs significantly reduced ERK protein phosphorylation, N-Myc protein phosphorylation at Serine 62, N-Myc protein stabilization, neuroblastoma cell proliferation and survival. Clonogenic assays showed that knocking down RP1NB1 with doxycycline completely abolished colony formation capacity of neuroblastoma cells stably transfected with doxycycline-inducible RP1NB1 shRNAs. Importantly, treatment with doxycycline in mice xenografted with neuroblastoma cells stably transfected with doxycycline-inducible RP1NB1 shRNA led to tumor eradication. In human neuroblastoma tissues from 600 neuroblastoma patients, high levels of RP1NB1 gene expression correlated with DEPD gene expression and poor patient prognosis. In conclusion, this study identifies the novel long noncoding RNA RP1NB1 as an important regulator of N-Myc protein stability and neuroblastoma tumorigenesis.