Neurotrophin signaling through tropomyosin receptor kinases contributes to survival and proliferation of non-Hodgkin lymphoma

ObjectiveNeurotrophin receptor signaling has been increasingly recognized as an important factor in the development and progression of a variety of malignancies. In order to analyze the potential contribution of neurotrophin signaling to lymphoma cell survival, we investigated the role of a neurotrophin axis in promoting survival and proliferation of non-Hodgkin lymphoma (NHL) cells.Materials and MethodsThe role of neurotrophins in the survival and proliferation of NHL cells was determined by exposing cells to the Trk-specific inhibitor, K252a, and then performing 3H-thymidine incorporation and Annexin-V/propidium iodide staining. The involvement of nuclear factor-κB (NF-κB) in this process was studied using Western blot, electrophoretic mobility shift assay, and immunofluorescence assays.ResultsHere we demonstrate that both primary NHL cells and diffuse large B-cell lymphoma cell lines express Trk receptors and their neurotrophin ligands. Furthermore, these cells are sensitive to the Trk-specific inhibitor, K252a, as evidenced by the inhibition of proliferation and/or induction of apoptosis. Analysis of the mechanism into the effects of K252a revealed that, in the OCI-LY3 cell line, K252a induced a subnuclear distribution of NF-κB resulting in the sequestration of RelA in the nucleolus, thereby inhibiting NF-κB−dependent gene transcription. This results in the loss of interleukin-6 production; a known survival-promoting signal for OCI-LY3, as well as many primary diffuse large B-cell lymphomas.ConclusionThus, Trk receptors represent a novel therapeutic target for the treatment of NHL.