PO-121 ALK dependant phosphoproteome and gene expression profiling of neuroblastoma cells

Introduction Receptor tyrosine kinases (RTKs) play important roles in cellular proliferation and differentiation. In addition, RTKs reveal oncogenic potential when their kinase activities are constitutively enhanced by point mutation, amplification, or rearrangement of the corresponding genes. We are investigating ALK (Anaplastic Lymphoma Kinase) tyrosine kinase in neuroblastoma (NB) - the most frequently occurring extracranial tumour in children, where ALK activating mutations are found. In this study we performed phosphoproteomic and a gene signature profiling of ALK activity from several different neuroblastoma cells comparing treatment with the first and third generations ALK inhibitors. Material and methods Crizotinib was one of the first ALK TKIs to be described; however the response in patients with ALK positive NB was poor. In contrast, robust and sustained clinical responses we seen in ALK rearranged IMT. Lorlatinib is a third generation ALK TKI with very positive responses in NSCLC. We treated two ALK addicted (CLB-BAR, CLB-GE) and one ALK non-addicted (SK-N-AS) NB cell lines with either crizotinib or lorlatinib and performed phosphoproteomic and RNAseq profiling to identify common targets for future combinational treatment for patients. Results and discussions Profiling of ALK addicted CLB-BAR and CLB-GE cell lines led to the identification of 3345 and 2252 phosphoproteins, respectively. Phosphorylation of the ALK receptor itself was decreased in both lines upon treatment with crizotinib or lorlatinib. Parallel RNAseq profiling was performed at 24 hours. Comparison with non-treated controls revealed 19 232 differently expressed genes. In ALK addicted cells phosphoproteomic analysis revealed more than 50 proteins that were dephosphorylated upon treatment with ALK TKIs. More than 400 genes were downregulated, and more than 600 were upregulated, upon treatment with either crizotinib or lorlatinib. As an outcome we obtained a list of predicted targets for further analysis. We focused on validation of downstream signalling molecules such as: FOXO3a/4, DUSP4 and ETV3/4. Conclusion In this study we established and compared phosphoproteomic and gene signature profiles of ALK activity in NB cells employing first and third generation ALK TKIs. This analysis has unveiled a number of leads for novel combinatorial treatment strategies for NB patients as well as an increased understanding ALK dependant signalling processes.