PO-181 Anaplastic lymphoma kinase addictive neuroblastoma cell lines are associated with growth upon treatment with MEK inhibitor trametinib

Abstract

Introduction The RAS-MAPK pathway is a major player in initiation and progression of multiple cancers where it can be hyper-activated by upstream regulatory proteins, such as receptor tyrosine kinases, phosphatases and GTPase’s. Several inhibitors targeting the RAS-MAPK pathway exhibit anti-cancer activity and are approved as a single agent in specific cancers. One such is the MEK inhibitor trametinib, which is included as a rational polytherapy strategy for treating EML4-ALK, EGFR and K-RAS mutant lung cancer and neuroblastoma containing hyper activating RAS-MAPK pathway mutations. In neuroblastoma, a heterogeneous disease, relapse cases display an increased rate of mutations of ALK, NRAS, NF1 genes, leading to hyperactivation of RAS-MAPK signalling. Targeting the RAS-MAPK pathways offers attractive options for combinatorial treatment together with ALK inhibitors since mono-treatment has not yet produced strong clinical results in ALK-positive neuroblastoma patients. Material and methods In order to determine which signalling core should be blocked for combinatorial treatment, we treated a panel of neuroblastoma cell lines using Trametinib, a MEK inhibitor. Resazurin assay was performed to evaluate cell viability. Protein levels were determined using western blotting. Results and discussions Here we investigate the response of ALK-positive neuroblastoma cell lines to MEK inhibition, employing trametinib. We show that pharmacological inhibition of MEK-ERK pathway results in increased levels of activation/phosphorylation of AKT and ERK5. This feedback response is regulated by SIN1 of mTORC2. Taken together, our results indicate that blocking MEK-ERK leads to ‘super-activation’ of AKT signalling core in ALK-positive neuroblastoma, increasing survival signals of these cells. Conclusion Our results contraindicate the use of MEK inhibitors as an effective therapeutic strategy in ALK-positive neuroblastoma.