High Expression of NTRK1 in ETV6::RUNX1 Positive Acute Lymphoblastic Leukaemia Drives Factor Independence and Sensitivity to Larotrectinib.

BACKGROUND: 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 survival was 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.