Immunolocalization of activated transforming growth factor beta1 in juvenile nasopharyngeal angiofibroma

Juvenile nasopharyngeal angiofibroma (JNA) is a histologically benign, locally aggressive neoplasm of the nasopharynx that exclusively affects male adolescents. It is known to be sensitive to androgens, but there are likely intermediary cytokines and/or growth factors that mediate aggressive stromal cell proliferation and angiogenesis. Transforming growth factor beta1 (TGF-beta1) is a polypeptide that is secreted in an inactive form, cleaved to produce an active form, and then deactivated in the tissues. It activates fibroblast proliferation and is known to induce angiogenesis.

To evaluate the presence of activated TGF-beta1 within the stroma of JNA specimens and to quantify the percentage of JNA specimens expressing the active growth factor.

Immunohistochemical analysis was performed on 19 specimens of JNA using a unique antibody that identifies only the activated form of TGF-beta1. The percentage of cells staining positively for activated TGF-beta1 was determined semiquantitatively by visual methods.

Of 19 cases stained, all 19 (100%) showed strong positive staining (2 cases with 33%-66% of cells staining and 17 with 66%-100% of cells staining). Activated TGF-beta1 was identified in stromal cell nuclei and cytoplasm and in the endothelium of the capillaries within all specimens of JNA.

The localization of activated TGF-beta1 to the fibroblasts and endothelial cells within JNA tumors suggests that TGF-beta1 may play a role in the stromal cell proliferation and angiogenesis associated with JNA. Additional receptor studies and more quantitative methods of analysis are needed to further define the role of TGF-beta1 in the pathogenesis of JNA.