The effect of calcitriol and its analogues on proliferation and hormone expression in cultured cells of thyroid medullary carcinomas.

The study aimed at evaluating the effects of calcitriol and of its analogues on the proliferation of TT and rMTC cells (human and rat line tumour cells originating from thyroid medullary carcinoma) and at examining the effects of the substances on the secretion of the principal hormones of the cells, calcitonin (CT) and calcitonin gene-related peptide (CGRP). Cells of thyroid medullary carcinoma (human TT cells and rat rMTC cells) were cultured for 5 days in the absence or in the presence of calcitriol and of its two analogues (PRI-1906 and PRI-2191) in concentrations of 10(-9) to 10(-6) M. Calcitriol and the applied analogues weakly inhibited proliferation of thyroid medullary carcinoma in in vitro conditions. The evident effect of analogues on hormone secretion points to their effect on the process of CT gene expression.