Neurotrophic receptor TrkB: Is it a predictor of poor prognosis for carcinoma patients?

The neurotrophic receptor tyrosine kinase TrkB, while binding its high affinity ligand brain-derived neurotrophic factor (BDNF), will play an essential role for nervous system development, neuronal survival, differentiation, and maintenance. However, accumulating evidences implies that TrkB signal pathway may also be involved in a variety of human cancers, in which TrkB is likely to play a role in initiation and metastasis of carcinomas. Overexpression of TrkB is often correlated with the tumorigenesis, angiogenesis and drug resistance in these malignancies, contributing significantly to the metastasis and aggressive phenotype of these poor prognosis tumors. The evidences to show the significant contribution of TrkB to malignancy not only came from solid tumors such as neoblastoma, pancreas cancer, Wilm's tumor and hepatocarcinoma, but also came from haematological malignancies such as Hodgkin lymphoma and multiple myeloma. In summary, besides its role in development and function of nervous system, TrkB is likely to also play a role in initiation and metastasis of carcinoma although it still remains to be further investigated and confirmed. Emerging data have suggested that TrkB may be a mediator as well as a marker of carcinogenesis and metastasis, therefore TrkB may be used as a valuable target for cancer therapy especially for the metastatic tumors with poor prognosis.