NTRK1/TrkA Activation Overrides the G₂/M-Checkpoint upon Irradiation

High expression of the receptor tyrosine kinase TrkA/NTRK1 is associated with a favorable outcome in several solid tumors of childhood including neuroblastoma. During development, TrkA/NTRK1 governs migration and differentiation of neuronal precursor cells, while it is associated with mitotic dysfunction and altered DNA damage response, among others, in neuroblastoma. Here, we used human neuroblastoma cell lines with inducible TrkA/NTRK1 expression to mechanistically explore the role of TrkA/NTRK1 signaling in checkpoint activation after DNA damage induced by ionizing radiation (IR). TrkA/NTRK1 activated cells showed increased short-term cell viability upon IR compared to vector control cells. This was accompanied by a deficient G₂/M-checkpoint at both low (1 Gy) and high doses (4 Gy) of IR. In a tightly controlled setting, we confirmed that this effect was strictly dependent on activation of TrkA/NTRK1 by its ligand, nerve growth factor (NGF). TrkA/NTRK1-expressing cells displayed impaired ATM and CHK1 phosphorylation, resulting in stabilization of CDC25B. In line with these findings, ATM or ATR inhibition recapitulated the effects of TrkA/NTRK1 activation on the IR-induced G₂/M-checkpoint. In conclusion, we here provide first evidence for a previously unrecognized function of NTRK signaling in checkpoint regulation and the response to IR.