RESUMO
BACKGROUND/AIM: Human ether à-go-go-1 (EAG1) potassium channels are promising anticancer targets. Calcitriol has antitumoural properties. This study investigated EAG1 regulation by calcitriol in normal and cancer cells. MATERIALS AND METHODS: Cancer cell lines from cervix, prostate, mammary gland, and normal placenta trophoblasts were cultured. Calcitriol was determined by HPLC. Gene and protein expression were assessed by real-time RT-PCR and western blot analysis, respectively. Calcitriol-synthesising enzyme CYP27B1 or vitamin D receptor (VDR), were transfected in cervical cancer SiHa cells. Cell proliferation was assayed with XTT. RESULTS: Calcitriol decreased EAG1 mRNA in all cell types, and EAG1 protein and proliferation in SiHa cells. VDR antagonist ZK-159222 prevented the calcitriol effect on EAG1 mRNA. CYP27B1-transfected cells produced more calcitriol and less EAG1 mRNA. EAG1 mRNA was more potently inhibited by calcitriol in VDR-transfected cells. CONCLUSION: EAG1 is a calcitriol target in normal and cancer cells and calcitriol is a potential therapy for cervical cancer.
Assuntos
Calcitriol/farmacologia , Canais de Potássio Éter-A-Go-Go/biossíntese , Neoplasias do Colo do Útero/metabolismo , 25-Hidroxivitamina D3 1-alfa-Hidroxilase/biossíntese , 25-Hidroxivitamina D3 1-alfa-Hidroxilase/genética , 25-Hidroxivitamina D3 1-alfa-Hidroxilase/metabolismo , Neoplasias da Mama/genética , Neoplasias da Mama/metabolismo , Calcitriol/análogos & derivados , Calcitriol/metabolismo , Linhagem Celular Tumoral , Regulação para Baixo/efeitos dos fármacos , Canais de Potássio Éter-A-Go-Go/genética , Feminino , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Células HeLa , Humanos , Masculino , Neoplasias da Próstata/genética , Neoplasias da Próstata/metabolismo , RNA Mensageiro/biossíntese , RNA Mensageiro/genética , Receptores de Calcitriol/antagonistas & inibidores , Receptores de Calcitriol/biossíntese , Receptores de Calcitriol/genética , Receptores de Calcitriol/metabolismo , Transfecção , Neoplasias do Colo do Útero/tratamento farmacológico , Neoplasias do Colo do Útero/genéticaRESUMO
Human placenta synthesizes and metabolizes 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)/calcitriol] through the activity of 25-hydroxyvitamin D(3)-1alpha-hydroxylase (CYP27B1) and 1,25(OH)(2)D(3)-24-hydroxylase (CYP24A1), the two key enzymes for Vitamin D metabolism. In this study, calcitriol rapidly generated intracellular cAMP accumulation in cultured human syncytiotrophoblast cells, which in turn enhanced hCG secretion, a marker of trophoblast endocrine activity. The effects of 1,25(OH)(2)D(3) upon the expression of CYP27B1 and CYP24A1 were also investigated. 1,25(OH)(2)D(3) and activators of the PKA signaling system decreased the expression of CYP27B1, whereas increased CYP24A1 gene transcription. The use of a selective inhibitor of PKA (H-89) prevented the effects of calcitriol on CYP27B1 gene and hCG secretion, but not on CYP24A1 transcription. Addition of ZK 159222, a Vitamin D receptor (VDR) antagonist, blocked the calcitriol-mediated upregulation of 24-hydroxylase gene expression but did not affect calcitriol-induced downregulation of CYP27B1 gene or hCG stimulation. In addition, our study also demonstrated a role of calcitonin on Vitamin D hydroxylases gene regulation in placenta. The overall data suggest that calcitriol downregulates CYP27B1 expression via a cAMP-dependent signaling pathway, whereas upregulates 24-hydroxylase gene expression through a VDR-dependent mechanism.