BDNF/TRKB PATHWAY IN SALIVARY GLAND CARCINOMAS

Objectives To evaluate the prognostic value of the brain-derived neurotrophic factor (BDNF), its tropomyosin receptor kinase B (TrkB), and 2 downstream targets of TrkB activation in salivary gland carcinomas (SGCs). Study Design Immunohistochemistry was preformed in 128 cases of SGC using antibodies against BDNF, phospho-TrkB, phospho-Akt, and phospho-S6. The slides were scanned and analyzed using the Aperio Scanscope CS Slide Scanner. Results BDNF, pTrkB, and pS6 were more expressed in adenoid cystic carcinoma (ACC) compared to mucoepidermoid carcinoma. In ACC, BDNF expression was associated with the presence of perineural invasion. Carcinoma ex-pleomorphic adenoma (CaExAP), the tumor with the worst prognosis in this study, also demonstrated an elevated expression of BDNF. However, BDNF/TrkB pathway immunoexpression was not associated with clinical outcomes. A direct correlation was observed between BDNF, pTrkB, pAkt, and pS6 expression. The colocalization of BDNF and pTrkB suggest an autocrine mechanism of this pathway in these malignancies. Conclusions Our results indicate that the BDNF/TrkB pathway is more expressed in some histologic types of SGC and might be associated with aggressive behaviors. Yet, these markers had no prognostic value in the present study.