Quinlan, L.Page, E.C.Rehn, J.McClure, B.J.Osborn, M.P.Moore, A.S.Kotecha, R.S.Henderson, M.J.Martin, M.Alvaro, F.Yeung, D.T.White, D.L.Heatley, S.L.2025-10-212025-10-212025Pediatric Blood and Cancer, 2025; 72(11):e31983-1-e31983-71545-50091545-5017https://hdl.handle.net/2440/147892Background: ETV6::RUNX1 is one of the most common recurrent genomic abnormalities in acute lymphoblastic leukaemia (ALL) and is associated with a good prognosis. High expression of NTRK1, encoding tropomyosin receptor kinase A (TrkA), confers a poor prognosis in other malignancies and may contribute to therapy resistance in patients with ETV6::RUNX1 B-ALL. Method: Relapse-free survivalwas estimated by the Kaplan–Meier and log-rank analyses. ETV6::RUNX1 and NTRK1 were isolated from patient cDNA and transduced into IL-3–dependent Ba/F3 cells. Proliferation was assessed via CellTiter-Glo-2.0 with the addition of the TrkA agonist, nerve growth factor (NGF). Sensitivity to the TRK inhibitor larotrectinib was assessed via Annexin V/7AAD staining and flow cytometry. Changes in TrkA signalling through effectors, ERK and AKT, were evaluated by western blotting. Results: Patients with ETV6::RUNX1 had increased NTRK1 expression in comparison with other B-ALL cases (p < 0.0001), with those overexpressing NTRK1 exhibiting a trend towards increased relapse. in vitro experiments revealed that only Ba/F3 ETV6::RUNX1+NTRK1 cells demonstrated IL-3 independence, indicative of leukaemic transformation (vs parental Ba/F3, p < 0.0001). These cells were sensitive to larotrectinib (LD50 161 nM) and significantly decreased phosphorylation of ERK and AKT (vs NGF p = 0.0004; p = 0.007, respectively).Conclusion: NTRK1 overexpression has not previously been reported in B-ALL and was associated with increased relapse in patients with ETV6::RUNX1 and NTKR1 overexpression. The in vitro success of larotrectinib treatment warrants further in vivo investigation and may be a viable therapeutic addition for patients with ETV6::RUNX1 B-ALL and NTRK1 overexpression.en© 2025 Wiley Periodicals LLC.ALL; ALL relapse; Cancer genetics; Hematology/Oncology; molecular diagnosis & therapy; Pediatric hematology/oncologyTumor Cells, CulturedHumansPyrazolesPyrimidinesReceptor, trkAOncogene Proteins, FusionRepressor ProteinsPrognosisDrug Resistance, NeoplasmAdolescentChildChild, PreschoolFemaleMaleCore Binding Factor Alpha 2 SubunitProto-Oncogene Proteins c-etsPrecursor Cell Lymphoblastic Leukemia-LymphomaETS Translocation Variant 6 ProteinJournal article10.1002/pbc.31983858545Page, E.C. [0000-0002-8990-2574]Rehn, J. [0000-0001-5043-6943]McClure, B.J. [0000-0002-5201-4127]Osborn, M.P. [0000-0002-1288-9930]Yeung, D.T. [0000-0002-7558-9927]White, D.L. [0000-0003-4844-333X]Heatley, S.L. [0000-0001-7497-6477]