Journal of Steroid Biochemistry & Molecular Biology 103 (2007) 781–785 Metabolism of vitamin D in the human choriocarcinoma cell line JEG-3 Euclides Avila a , Lorenza D´ ıaz a,∗ , David Barrera a , Celeste Arranz b , Ali Halhali a , Fernando Larrea a a Departamento de Biolog´ ıa de la Reproducci´ on, Instituto Nacional de Ciencias M´ edicas y Nutrici ´ on Salvador Zubir ´ an, Vasco de Quiroga No. 15, Tlalpan 14000, Mexico, D.F., Mexico b Instituto Nacional de Endocrinolog´ ıa, Hospital Comandante “Manuel Fajardo”, Zapata y D, Vedado, Ciudad de La Habana, Cuba Abstract Calcitriol is an antiproliferative prodifferentiating secosteroid that exerts a protective role for some kinds of cancer. Alterations in 25-hydroxyvitamin D-1-hydroxylase (CYP27B1) activity have been found in some tumor cells, but there are no studies performed in human choriocarcinoma. In the present work, calcitriol production and CYP27B1 gene regulation were studied in the human choriocarcinoma cell line JEG-3, and compared with normal human syncytiotrophoblasts (hS) in culture. In JEG-3 cells, secretion of [ 3 H]calcitriol was significantly less (P < 0.001) than in hS (45 ± 17 fmol/mg protein versus 174 ± 87 fmol/mg protein, respectively; n = 8). CYP27B1 mRNA was similar in both JEG-3 and hS cells; but the protein was detected only in hS extracts. In contrast to the hS, JEG-3 CYP27B1 gene expression was not regulated by calcitriol or by a cAMP analogue. Our results indicate that in JEG-3 cells calcitriol production is diminished due to CYP27B1 dysregulation and low protein content, and suggest that hyperproliferation could be a consequence of these alterations. © 2006 Elsevier Ltd. All rights reserved. Keywords: Trophoblast; Placenta; CYP27B1; Calcitriol; cAMP; Cancer 1. Introduction Vitamin D 3 derived from 7-dehydrocholesterol is acti- vated to 1,25-dihydroxyvitamin D 3 (1,25(OH) 2 D 3 or calcitriol) after two successive hydroxylations in the liver and kidney [1]. The rate-limiting step for calcitriol production is the 25-hydroxyvitamin D 3 -1-hydroxylase (1-hydroxylase, CYP27B1). Most of calcitriol effects are mediated by the vitamin D receptor (VDR), regulating the expression of genes whose promoters contain specific vitamin D response elements (VDREs). During gestation, placenta is an important extrarenal source of calcitriol [2,3]. Human syncytiotrophoblasts (hS) synthesize calcitriol from 25-hydroxyvitamin D 3 [4], and express CYP27B1 and VDR [5]. The rates of extrarenal calcitriol synthesis and degrada- ∗ Corresponding author. Tel.: +52 55 55 73 11 60; fax: +52 55 56 55 98 59. E-mail address: lorenzadiaz@gmail.com (L. D´ ıaz). tion are under the control of local factors, which optimize the levels of the secosteroid for cell-specific actions. Con- sequently, the regulation of extrarenal CYP27B1 may be different from that of the renal enzyme [1]. In the nor- mal trophoblast, calcitriol production is inhibited by cAMP and is produced in a lesser amount as the cell differentiates into syncytium [5]. Extrarenal calcitriol seems to accomplish autocrine/paracrine functions; however, little is known about the actions of this hormone in the placenta [2], and nothing is known about how placental calcitriol production is affected in the malignant transformation of the trophoblast. In the present work we studied calcitriol production and CYP27B1 abundance in choriocarcinoma cells and results were com- pared with normal hS. Additionally, the effects of calcitriol and cAMP upon CYP27B1 expression in the human chorio- carcinoma cell line JEG-3 were also studied. The results of this study will help to understand the biological function of locally produced calcitriol, including the role of vitamin D metabolism under normal and pathological conditions. 0960-0760/$ – see front matter © 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.jsbmb.2006.12.047