Περίληψη:
Fas ligand (FasL) induces apoptosis by cross-linking the Fas receptor
and is expressed by cells of the immune system. Recently, Fast was found
in malignant tumors, suggesting that it helps them escape immune
surveillance by eliminating infiltrating lymphocytes. We investigated
the presence of Fast immunohistochemically in 48 thyroid carcinomas and
by Western blotting and RT-PCR in 5 thyroid carcinoma cell lines. We
found that in contrast to normal thyroid tissue, Fast was highly
expressed in all papillary, follicular, and Huerthle carcinomas.
Medullary carcinomas lacked or had minimal Fast expression. In papillary
carcinomas, high levels of expression correlated independently with
aggressive histology and unfavorable clinical presentation. Fast was
also present in all thyroid cell lines. Thyroid carcinoma cells killed
Fas-sensitive targets in a FasL-dependent manner in a coculture
experiment. Cross-linking of Fas induced apoptosis in thyroid carcinoma
cells only in the presence of cycloheximide. We conclude that Fast is
specifically expressed in thyroid carcinomas of follicular epithelial
origin, may help them evade the immune system, and may have prognostic
implications in papillary carcinoma, as it is associated with a more
aggressive phenotype. Thyroid carcinoma cells avoid Fas-mediated suicide
possibly by expressing an inhibitor of the Fas apoptotic pathway.
Συγγραφείς:
Mitsiades, N
Poulaki, V
Mastorakos, G
Tseleni-Balafouta, S
and Kotoula, V
Koutras, DA
Tsokos, M
