C-MET EXPRESSION OF THYROID-TISSUE WITH SPECIAL REFERENCE TO PAPILLARY CARCINOMA

It has become clear that papillary carcinomas of the thyroid often exp ress the receptor for c-Met/hepatocyte growth factor (HGF) receptor, b ut little is known about the role of the HGF;and c-Met system in the p athogenesis of thyroid carcinoma, In this study, the expression of c-M et/HGF receptor was evaluated in thyroid tissue by western blot and im munohistochemistry, and compared with the concentration elf HGF. Clini copathological characteristics were also compared. Fifteen of 20 papil lary carcinomas (75%) showed c-Met bands of 145 kDa, No or only a low frequency of c-Met expression was detected in healthy thyroid tissue ( 0/5), thyroiditis or Basedow's disease (0/2), adenomatous goiters (0/8 ), follicular adenomas (1/9, 11%) and undifferentiated carcinomas (0/2 ), These results were confirmed by immunohistochemistry,but a relative ly higher frequency of c-Met expression was detected in adenomatous go iters (25%), follicular adenoma (44%) and papillary carcinoma (100%) u sing formalin-fixed and paraffin-embedded materials,,A strong immunore action for c-Met was observed in the tumor cytoplasm of papillary carc inomas among the fibrous tissues situated at the periphery of the tumo r. The densitometric:ally measured expression of c-Met had no relation to tumor stage in papillary carcinoma, but did correlate to the conce ntration of HGF in papillary carcinomas. In conclusion, in thyroid les ions, c-Met was highly expressed specifically in the cytoplasm of papi llary carcinomas. c-Met expression was not related to the aggressivene ss of the tumor but was related to the concentration of HGF, which was probably derived from the stroma, Also, the c-Met system might play a role in the pathogenesis of papillary carcinoma of the thyroid.