NTSR2 and B-cell chronic lymphocytic leukemia: BDNF’s expression is high on the surface of CLL cells and by binding the neurotensin receptor 2-tropomyosin-related kinase receptor B (NTSR2-TrkB) complex which is highly expressed on CLL cells surface as well, activates B-cell lymphoma 2 protein (BCL-2) and other signaling pathways, leading to an anti-apoptotic effect [145].