Expression of transforming growth factor-β receptor type 1 and type 2 in human sporadic vestibular Schwannoma

Expression of the transforming growth factor-β (TGF-β) protein family in the peripheral nervous system is well established, but the role of their cognate receptors TGF-β receptor type 1 (R1) and type 2 (R2) has been less well studied. TGF-β plays an essential role in Schwann cell proliferation and differentiation, and is involved in neurotrophic effects of several neurotrophic substances. TGF-β is also expressed in benign peripheral nervous system tumors such as vestibular schwannomas. In the present study, we aimed to detect TGF-β R1 and R2 in a total of 40 sporadic vestibular schwannomas using immunohistochemistry, and correlated the findings to essential clinicopathologic data. TGF-β, TGF-β R1, and TGF-β R2 mRNA was further analyzed by RT-PCR in six vestibular schwannomas. TGF-β R1 immunoexpression was found in about 95% of the tumors. TGF-β R1 was equally present in Antoni A and Antoni B areas of the tumors. TGF-β R2 was found immunohistochemically in 77%. In addition, all tumors showed strong expression of TGF-β. No correlation between TGF-β R1 or R2 expression and clinicopathologic parameters such as age, sex, clinical symptoms, growth pattern, and proliferation acitivity as measured by Ki-67 (MIB-1) staining was found. Moreover, all schwannomas studied contained TGF-β, TGF-β R1, and TGF-β R2 mRNA. Therefore, the TGF-β/TGF-β R1 and -R2 system is present in human schwannomas, but its biologic role for tumor development and growth remains unclear.