Transforming growth factor-beta 1 expression in human acoustic neuroma

Hypothesis: The differing clinical behavior of acoustic neuroma (AN) may be explained by the presence of specific biological features involved in tumo rigenesis and growth. Background: Transforming growth factor (TGF) beta 1 is known to participate in the regulation of peripheral nerve tumors, modulating cell proliferatio n and differentiation with mechanisms different from those of glial growth factors (GGF) and fibroblastic growth factors (FGF), which are responsible for Schwann cells' mitogen activity. Methods: Surgically removed human AN specimens were fixed in formalin and e mbedded in paraffin for immunohistochemistry studies. Expression and locali zation of TGF-beta 1 in different tumor regions were assessed after incubat ion of paraffin sections with a mouse monoclonal anti-TGF beta 1 antibody ( DBA, Milan, Italy). Clinically, the time elapsed between the beginning of s ymptomatology and AN size as shown by preoperative computed tomography, mag netic resonance imaging, or both was calculated as rough value of growth ra te, which enabled slow-growing and fast-growing ANs to be distinguished. Results: Eighty-four percent of AN specimens expressed TGF-beta 1 positivit y at the level of the cytoplasm of the Schwann cells. TGF-beta 1 reactivity was also shown in the blood vessel walls (96.15%) and the tumor capsule (8 0.86%). TGF-beta 1 reaction appeared higher in Antoni A regions than in Ant oni B regions. No significant relationship was found between TGF-beta 1 pos itivity and AN growth rate in the two groups. Conclusions: TGF-beta 1 could participate in the biological behavior of AN, particularly as an important factor of tumor growth prediction by allowing rapidly progressive or potentially recurrent tumors to be differentiated f rom slow-growing tumors that are unlikely to recur. The clinical course of patients with AN is currently still of little help in predicting the rate o f AN growth.