BDNF (brain-derived neurotrophic factor) and TrkB (tropomyosin receptor kinase B) are expressed in several tumor types. However, the existence of BDNF and TrkB in human bladder cancer, especially transitional cell carcinoma (TCC), has not been established. In this study, commercial TCC tissue arrays were used. Slides of paraffin-fixed human bladder tissues included all grades of TCC (13, 30 and 22 tissue samples in grade I, II and III, respectively), superficial and invasive TCC (31 and 34 tissue samples, respectively), paired malignancy-uninvolved urothelium (35 tissue samples) and normal urothelial tissues (12 tissue samples). The intensities of BDNF and TrkB immunostaining were graded as background, mild and strong (score as 0, 1 and 2, respectively). The results showed significantly overexpressed BDNF and TrkB in TCC samples compared to normal urothelium. According to grade assignment of TCC samples, BDNF in grade III and TrkB in grade I and III appeared to be overexpressed. BDNF and TrkB were overexpressed in superficial TCC samples according to staging classification. The score between the paired TCC and its uninvolved urothelium was not statistically different. In conclusion, the existence of overexpressed BDNF and TrkB in human TCC has been demonstrated in our study. A strategy involving BDNF/TrkB blockade may be a new hope for TCC target therapy.

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