Neuroblastoma is the most common solid tumour in early childhood, and accounts for approximately 15% of all childhood cancer death. N-Myc gene amplification occurs in one quarter to one third of human neuroblastoma tissues, and the majority of patient with neuroblastoma due to N-Myc gene amplification die of the disease. We performed RNA sequencing experiments, and identified 5 transcripts, including RP1X, which were considerably differentially expressed between N-Myc gene amplified and non-amplified human neuroblastoma cell lines. Affymetrix microarray studies revealed that DEPDC was one of the few genes considerably down-regulated in neuroblastoma cells after RP1X depletion. Chromatin immunoprecipitation assays showed that knocking-down RP1X expression reduced histone H3 lysine 4 trimethylation, a marker for active gene transcription, at the DEPDC gene promoter. Depletion of RP1X or DEPDC 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 RP1X with doxycycline completely abolished colony formation capacity of neuroblastoma cells stably transfected with doxycycline-inducible RP1X shRNA. Importantly, treatment with doxycycline in mice xenografted with neuroblastoma cells stably transfected with doxycycline-inducible RP1X shRNA, led to tumour eradication. In human neuroblastoma tissues from 600 neuroblastoma patients, high levels of RP1X gene expression correlated with DEPDC gene expression and poor patient prognosis. In conclusion, this study identifies the novel long noncoding RNA RP1X as an important regulator of N-Myc protein stability and neuroblastoma tumourigenesis.

Citation Format: Pei Y. Liu, Andrew E. Tee, Bernard Atmadibrata, Pieter Mestdagh, Jo Vandesompele, Marcel Dinger, Tao Liu. Eradication of neuroblastoma by suppressing the expression of a single long noncoding RNA. [abstract]. In: Proceedings of the AACR Special Conference on Noncoding RNAs and Cancer: Mechanisms to Medicines ; 2015 Dec 4-7; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2016;76(6 Suppl):Abstract nr B13.