mRNA Expression Level of ALK in Neuroblastoma Is Associated with Histological Subtype, ALK Mutations and ALK Immunohistochemical Protein Expression

ALK is related to poor survival in neuroblastoma patients. We investigated the prognostic relevance of ALK mRNA expression and the relationship with ALK immunohistochemical expression, histological subtype and ALK aberrations. Whole transcriptome sequencing data were available from 54 patients. Overall survival (OS) and event-free survival (EFS) were estimated with Kaplan–Meier’s methodology. ALK protein expression was analyzed by immunohistochemistry. ALK aberrations were detected using whole exome sequencing, single nucleotide polymorphism array, next generation sequencing and/or fluorescence in situ hybridization. OS was 74.8% and EFS was 60%. ALK mRNA expression was not associated with OS (HR 1.127, 95% CI (0.812–1.854), p = 0.331) and adjusted EFS (HR 1.134, 95% CI (0.783–1.644), p = 0.505), but was associated with histological subtype (OR 1.914, 95% CI (1.083–3.382), p = 0.025) and ALK protein expression (negative versus weak: OR 2.829, 95% CI (1.290–6.204), p = 0.009) (negative versus moderate/strong: OR 2.934, 95% CI (0.889–9.679), p = 0.077). ALK mutated tumors had significantly higher ALK mRNA expression than non-mutated tumors (p < 0.001). MYCN-amplified neuroblastomas have higher MYCN mRNA expression (p ≤ 0.001), but not ALK mRNA expression (p = 0.553). ALK mRNA expression is higher in ALK mutated neuroblastomas and is associated with poorer differentiation degree and higher protein expression. ALK mRNA expression is not significantly associated with OS and EFS.