Caveolin-1 and 14-3-3 sigma expression in follicular variant of thyroid papillary carcinoma

There are two prominent types of thyroid carcinoma, papillary carcinoma (PC) and follicular carcinoma (FC) arising from thyroid follicular cells, which have different biological characteristics. The follicular variant of papillary carcinoma (FVPC) has a structure similar to FC, although it is classified as a subtype of PC. We have previously demonstrated that caveolin-1, a major component of caveolae and an inhibitor of growth signal transduction, and 14-3-3 sigma, a regulator of the cell cycle and signal transduction, are frequently expressed in pure PC, but not in FC. In this study, we investigated these expressions in FVPC and FC. Caveolin-1 and 14-3-3 sigma were expressed in 96.2% and 92.3% of FVPC, respectively. However, almost all FC, with only a few exceptions, were negative for these findings, indicating that these proteins were more frequently expressed in FVPC than in FC (p < 0.0001). These findings suggest that caveolin-1 and 14-3-3 sigma positively or negatively regulate the development of FVPC but not that of FC, reflecting the difference of biological characteristics of these two types of carcinoma.