Expression of basic fibroblast growth factor in thyroid disorders

Morphologic and biologic studies were undertaken to clarify the biologic significance of basic fibroblast growth factor (bFGF) in human thyroid neoplasms. A total of 71 malignant tumors (50 papillary carcinomas, 14 follicular carcinomas, 7 anaplastic carcinomas), 11 follicular adenomas, 6 adenomatous goiters, and 6 Graves' disease tissues were examined employing immunohistochemical methods (avidin-biotin-peroxidase complex technique). An affinity-purified polyclonal rabbit antiserum to human bFGF was used as a primary antibody. The eluate of malignant thyroid tumor tissues from the heparin-Sepharose column was examined by Western blot analysis to elucidate the molecular weight form. With immunohistochemical staining, bFGF was frequently detected in the cytoplasm of malignant thyroid tumors compared to tissues of the benign diseases and normal controls. With anaplastic carcinoma, immunoreactivity of the tumor cells was particularly strong. In the correlative analyses between UICC TNM classification and bFGF staining in papillary carcinoma, there were significant differences when relating positive staining to the grade of nodal metastases. By Western blot analysis, the bFGF immunoreactivity was specifically detected in the two forms, with molecular weights of 18 and 33 kDa. The high-molecular-weight form was detected in only anaplastic carcinoma. The present investigations demonstrated a close correlation between the expression of bFGF and the degree of malignancy. bFGF might play an important role in promoting lymph node metastases. Moreover, the high-molecular-weight form of bFGF might have an intense influence on tumor growth.