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The effects of administration of vitamin D₃ and Seocalcitol on MNU-induced carcinogenesis of mammary gland in Sprague-Dawley rats have been investigated. Administration of both substances in a weekly dose of 7 μg/kg caused prolonged latency of mammary gland tumors. The latency of tumors was markedly prolonged for 30-40 days by Seocalcitol. Using PET analysis, reduction in [¹⁸F]2-fluoro-2-deoxy-d-glucose (FDG) uptake or tumor volume in tumors chemopreventively treated with vitamin D₃ were detected in MNU-induced tumors, vitamin D₃ reduced expression of 25-hydroxylase (25OHase) (p<0.01) and 24-hydroxylase (24OHase) (p<0.01) and Seocalcitol 24OHase. Positive regulation of 25OHase mRNA level after the treatment with vitamin D₃ was observed in liver, while in kidney, vitamin D₃ and Seocalcitol induced expression of 24OHase was significant. Our observations indicate a cross talk between respective pathways of VDR, RARs/RXRs, TRs and ERs in carcinogenesis process., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)

In the present work, the effects of colchicine (COL) and/or all-trans retinoic acid (ATRA) on expression of rexinoid receptors (RXRs) (alpha, beta, gamma), thyroid hormone receptor alpha and coregulators N-CoR, SMRT and SRC-1 mRNA in primary rat hepatocytes as a model of no-proliferating cells were investigated. Treatment with these components, either alone or in combination, induced differences of the expression profiles between distinct treatment groups.

Cellular signaling by glucocorticoid receptor and aryl hydrocarbon receptor is restricted by microtubules interfering agents (MIAs). This leads to down-regulation of drug metabolizing enzymes and drug interactions. Here we investigated the effects of all-trans-retinoic acid (ATRA) and MIAs, i.e. colchicine, nocodazole and taxol on the regulation of retinoic acid receptor (RAR) genes in primary cultures of rat hepatocytes. ATRA (1microM) down-regulated RARalpha and RARgamma mRNAs (decrease 23% and 41%, respectively) whereas it up-regulated RARbeta mRNA (4.3-fold induction). All MIAs diminished the expression of RARs in dose-dependent manner; the potency of MIAs increased in order NOC

Dihydroxyvitamin D(3) is known to affect broad spectrum of various biochemical and molecular biological reactions in organisms. Research on the role and function of nuclear vitamin D(3) receptors (VDR) playing a role as dihydroxyvitamin D(3) inducible transcription factor belongs to dynamically developing branches of molecular endocrinology. In higher organisms, full functionality of VDR in the form of heterodimer with nuclear 9-cis retinoic acid receptor is essential for biological effects of dihydroxyvitamin D(3). This article summarizes selected effects of biologically active vitamin D(3) acting through their cognate nuclear receptors, and also its potential use in therapy and prevention of various types of cancer.