Medullary thyroid carcinoma (MTC) originates from parafollicular C cells. Estrogen receptor β(ERβ) expressionwas detected in normal parafollicular C cells and MTC tumor tissue, but ERα expression in MTC tumors still remains undetermined. The appearance and loss of ERα or ERβ expression has been known to play a role in the development and progression of many human cancers. We performed immunohistochemical studies of ERα, ERβ, and Ki67, a mitotic index, in 11 human MTC tissue samples. ERα was detected in 10 cases (91%), and ERβ expression was observed in 8 cases (72.7%). A majority (8/10) of ERα-positive tumors showing ERβ Ki67 expression was detected in three cases (27.3%). Neither clinical parameters nor tumor node metastasis (TNM) tumor staging was correlated with the positivity for ERs or Ki67. To investigate the biological role of each ER, we used ER-negative MTC TT cells and adenoviral vectors carrying ERα (Ad-ERα), ERβ (Ad-ERβ), estrogen response element (ERE)-Luc (Ad-ERE-Luc), and activator protein 1 (AP1)-Luc (Ad-AP1-Luc). Estrogen stimulated and anti-estrogen, ICI 182 780, suppressed ERE reporter activity in TT cells expressing ERα or ERβ, suggesting that both ERs use the same classical ERE-mediated pathway. Ad-ERα infection stimulated TT cell growth; in contrast, Ad-ERβ infection suppressed their growth. Apoptosis was detected in Ad-ERβ-infected TT cells. Estrogen and anti-estrogen suppressed AP1 activity in Ad-ERα-infected cells, whereas upon Ad-ERβ infection estrogen further stimulated AP1 activity which in turn is suppressed by anti-estrogen, suggesting that each ER acts differently through a non-ERE-mediated pathway. Our results suggest that ERα and ERβ may play different roles in MTC tumor growth and progression.
Role of cytology in differentiating anaplastic thyroid carcinoma with osteoclast like giant cells from giant cell variant of medullary thyroid carcinoma
