NTRK1/TrkA Activation Overrides the G(2)/M-Checkpoint upon Irradiation

SIMPLE SUMMARY: Neuroblastoma (NB) is a solid childhood tumor and needs to be treated with multimodal therapy including radiation in advances stages. TrkA/NTRK1 expression is a hallmark of NB with excellent prognosis, but the impact of TrkA/NTRK1 on radiation response is largely unknown. Here, we report that human neuroblastoma cell lines engineered to express TrkA/NTRK1 in tightly controlled systems fail to activate the G2/M cell cycle checkpoint upon irradiation, which recapitulates the effects of ATM or ATR inhibition. Our findings point to a hitherto unrecognized TrkA/NTRK1-mediated wiring of the radiation response in NB cells. ABSTRACT: 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 G(2)/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 G(2)/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.