Neuroblastoma is a childhood extracranial solid tumour that is associated with a number of genetic changes. Included in these genetic alterations are mutations in the
kinase domain of the
anaplastic lymphoma kinase (ALK)
receptor tyrosine kinase (RTK), which have been found in both somatic and familial
neuroblastoma. In order to treat patients accordingly requires characterisation of these mutations in terms of their response to ALK
tyrosine kinase inhibitors (TKIs). Here, we report the identification and characterisation of two novel
neuroblastoma ALK mutations (A1099T and R1464STOP), which we have investigated together with several previously reported but uncharacterised ALK mutations (T1087I, D1091N, T1151M, M1166R, F1174I and A1234T). In order to understand the potential role of these ALK mutations in
neuroblastoma progression, we have employed cell culture-based systems together with the model organism Drosophila as a readout for
ligand-independent activity. Mutation of ALK at position 1174 (F1174I) generates a gain-of-function receptor capable of activating intracellular targets such as ERK (
extracellular signal regulated kinase) and STAT3 (
signal transducer and activator of transcription 3) in a
ligand-independent manner. Analysis of these previously uncharacterised ALK mutants and comparison with ALK(F1174) mutants suggests that ALK mutations observed in
neuroblastoma fall into three classes. These classes are: (i) gain-of-function
ligand-independent mutations such as ALK(F1174l), (ii)
kinase-dead ALK mutants, e.g. ALK(I1250T) (Schönherr et al., 2011a) and (iii) ALK mutations that are
ligand-dependent in nature. Irrespective of the nature of the observed ALK mutants, in every case the activity of the mutant ALK receptors could be abrogated by the ALK inhibitor
crizotinib (
Xalkori/
PF-02341066), albeit with differing levels of sensitivity.