Expression of Transforming Growth Factor-β₁ and Transforming Growth Factor-β Type-II Receptor mRNA in Papillary Thyroid Carcinoma

Transforming growth factor-β₁ (TGF-β₁) is a potent inhibitor of epithelial cell proliferation. Signal transduction by TGF-β₁ involves direct binding to the TGF-β₁ Type-II receptor and then the formation of a heterodimeric complex of TGF-β Type-I and Type-II receptor. To explore the role of TGF-β₁ in thyroid carcinoma, we examined the expression of TGF-β₁ and TGF-β Type-II receptor mRNA by northern blotting analysis in both 14 papillary thyroid carcinomas and surrounding normal thyroid tissues. Relative mRNA level was determined by scanning densitometry of the autoradiogram and corrected for loading differences using a human β-actin cDNA probe. The relative mRNA levels of TGF-β₁ in 12 out of 14 papillary thyroid carcinomas were higher than those in surrounding normal thyroid tissues. In contrast, the relative mRNA levels of TGF-β Type-II receptor were reduced to 60.1 ± 18.3% of those of normal thyroid tissues in 10 papillary thyroid carcinomas. There were no clear relationships between the relative mRNA levels for TGF-β₁ and TGF-β Type-II receptor and the histological characteristics of papillary thyroid carcinomas. The relative mRNA levels for TGF-β₁ and TGF-β₁ Type-II receptor did not show significant differences in thyroid carcinomas with or without lymph node metastases. There was a negative correlation between the TGF-β Type-II receptor mRNA level and tumor size, while no significant correlation was observed between the TGF-β₁ mRNA level and tumor size. In conclusion, most papillary thyroid carcinomas overexpress TGF-β₁ mRNA but exhibit a reduction in TGF-β Type-II receptor mRNA. The reduction of TGF-β Type-II receptor mRNA may play a role in the pathogenesis of papillary thyroid carcinoma.

Key words

Transforming Growth Factor-β₁ - Transforming Growth Factor-β Type-II Receptor - Papillary Thyroid Carcinoma - mRNA