Blockade of MYCN-dependent transcription using orally-bioavailable CDK9 inhibitors

Neuroblastoma is a common solid tumor that accounts for 15% of cancer deaths in children and amplification of the MYCN oncogene is the most common genomic alteration in aggressive tumors. Although MYCN is expressed as a tumor-specific oncoprotein in poor-outcome neuroblastoma, making it a therapeutic target of great potential importance, no drugs with significant activity against MYCN or MYC are available for clinical use. The aim of this study was to explore the sensitivity of neuroblastoma cells in vitro and in vivo to the tri-substituted purine CDK inhibitors, CYC065, chemical analogues of seliciclib, (Cyclacel Ltd). Kelly, SKNAS, BE(2)C, and SH-SY-5Y neuroblastoma cell lines were analyzed in this study. Kelly, SKNAS cells, BE(2)C, and SH-SY-5Y (3 biological replicates) treated with CYC065 and compared with cells treated with the equivalent of DMSO (3 biological replicates). Total RNA was isolated from cells and tumor tissue using the RNAeasy plus minikit (Qiagen), labelled and hybridized to Gene Chip® human transcriptome expression array (Affymetrix). 10 mice were analyzed in this study. 4 TH-MYCN tumors treated with CYC065 were compared with 6 untreated TH-MYCN tumors. Total RNA was isolated from cells and tumor tissue using the RNAeasy plus minikit (Qiagen), labelled and hybridized to Gene Chip® mouse transcriptome expression array (Affymetrix).