24-25-dihydroxyvitamin-d-3 and Carcinoma

We utilized the TT cell, a human C-cell line derived from a medullary thyroid carcinoma, to study the effects of 1,25-dihydroxyvitamin D3 on cell growth and expression of the calcitonin gene. The growth rate of cells treated for 8 days with 1,25-dihydroxyvitamin D3 did not differ significantly from control or 24,25-dihydroxyvitamin D3 treated cells. Total RNA was isolated, and calcitonin and calcitonin gene-related peptide (CGRP) levels were measured by hybridization. 1,25 D3 lowered calcitonin and CGRP mRNA levels in a time- and dose-dependent fashion; 24,25 D3 had no effect. Northern blots revealed a decrease in the mature mRNA as well as the common precursor forms, indicating a transcriptional effect of 1,25 D3.

Topics: 24,25-Dihydroxyvitamin D 3; Calcitonin; Calcitonin Gene-Related Peptide; Calcitriol; Carcinoma; Dihydroxycholecalciferols; Humans; Kinetics; Neuropeptides; Nucleic Acid Hybridization; RNA, Messenger; Thyroid Neoplasms; Tumor Cells, Cultured

We previously reported increased mean serum 1,25-dihydroxyvitamin D (1,25-(OH)2D) and increased trabecular bone remodelling in patients with medullary thyroid carcinoma (MCT) and hypercalcitoninaemia. In the present paper we report that serum 1,25-(OH)2D and trabecular bone remodelling decreased following surgical cure for MCT and hypercalcitoninaemia in 4 patients despite no detectable post-surgical hypoparathyroidism or hypothyroidism. The results obtained in the present small number of patients suggest that the altered vitamin D metabolism and trabecular bone remodelling in patients with MCT is caused by the hypercalcitoninaemia.

Topics: 24,25-Dihydroxyvitamin D 3; Adult; Aged; Bone and Bones; Calcitonin; Calcitriol; Carcinoma; Dihydroxycholecalciferols; Female; Humans; Male; Middle Aged; Parathyroid Hormone; Thyroid Hormones; Thyroid Neoplasms; Vitamin D