IMMUNOELECTRON MICROSCOPIC DEMONSTRATION OF REGULATED PATHWAY FOR CALCITONIN AND CONSTITUTIVE PATHWAY FOR CARCINOEMBRYONIC ANTIGEN IN THE SAME CELLS OF HUMAN MEDULLARY CARCINOMAS OF THYROID-GLANDS
Ry. Osamura et al., IMMUNOELECTRON MICROSCOPIC DEMONSTRATION OF REGULATED PATHWAY FOR CALCITONIN AND CONSTITUTIVE PATHWAY FOR CARCINOEMBRYONIC ANTIGEN IN THE SAME CELLS OF HUMAN MEDULLARY CARCINOMAS OF THYROID-GLANDS, Modern pathology, 10(1), 1997, pp. 7-11
The human medullary carcinomas are well known to secrete calcitonin (C
T) as a neuroendocrine peptide and carcinoembryonic antigen (CEA) as a
serum protein that is integrated into the cell membrane. This ultrast
ructural study is designed to elucidate whether CT and CEA are secrete
d via two different intracellular secretory pathways, a regulated path
way and a constitutive pathway. The immunoelectron microscopic postemb
edding method, performed on four cases of the human medullary carcinom
as of the thyroid using plastic embedding material, disclosed two dist
inct different localization patterns for CT and CEA. CT was localized
exclusively in dense cored secretory granules. CEA was present in the
cell membrane and in the secretory vesicles. The secretory granules we
re completely negative for CEA. The trans-Golgi networks were also pos
itive for CT and CEA. Electron microscopic double staining confirmed t
hese localization in the same carcinoma cells, These observations sugg
est the presence of two distinct pathways in the endocrine cancer cell
s, i.e., the regulated pathway for CT and the constitutive pathway for
CEA.