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The vitamin D endocrine system is essential for calcium metabolism and skeletal integrity. 1,25-dihydroxyvitamin D 3 [1,25(OH) 2 D 3 ] regulates bone mineral homeostasis and acts directly on osteoblasts. In the present study we characterized the transcriptional regulation of the class 3 semaphorin (Sema3) gene family by 1,25(OH) 2 D 3 in osteoblastic cells. Class 3 semaphorins are secreted proteins that regulate cell growth, morphology and migration, and were recently shown to be involved in bone homeostasis. In ST2, MC3T3-E1 and primary calvarial osteoblast cell cultures we found that all members of the Sema3 gene family were expressed, and that Sema3e and Sema3f were the most strongly induced 1,25(OH) 2 D 3 target genes among the studied cell types. In addition, transcription of Sema3b and Sema3c was upregulated, whereas Sema3d and Sema3g was downregulated by 1,25(OH) 2 D 3 in different osteoblastic cells. Chromatin immunoprecipitation analysis linked to DNA sequencing (ChIP-seq analysis) revealed the presence of the vitamin D receptor at multiple genomic loci in the proximity of Sema3 genes, demonstrating that the genes are primary 1,25(OH) 2 D 3 targets. Furthermore, we showed that recombinant SEMA3E and SEMA3F protein were able to inhibit osteoblast proliferation. However, recombinant SEMA3s did not affect ST2 cell migration. The expression of class 3 semaphorins in osteoblasts together with their regulation by 1,25(OH) 2 D 3 suggests that these genes, involved in the regulation of bone homeostasis, are additional mediators for 1,25(OH) 2 D 3 signaling in osteoblasts., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Active vitamin D3, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], and its synthetically derived analogs possess potent anticancer properties. In breast cancer (BC) cells, 1,25(OH)2D3 blocks cell proliferation and induces apoptosis through different cell-type specific mechanisms. In this study, we evaluated if the combination of the potent vitamin D3 analog, inecalcitol, with a selective CDK4/6 inhibitor, palbociclib, enhanced the antiproliferative effects of both single compounds in hormone-sensitive (ER+) BC, for which palbociclib treatment is already approved, but also in triple-negative BC (TNBC). Inecalcitol and palbociclib combination treatment decreased cell proliferation in both ER+ (T47D-MCF7) and TNBC (BT20-HCC1143-Hs578T) cells, with a more pronounced antiproliferative effect in the former. In ER+ BC cells, the combination therapy downregulated cell cycle regulatory proteins (p)-Rb and (p)-CDK2 and blocked G1-S phase transition of the cell cycle. Combination treatment upregulated p-mTOR and p-4E-BP1 protein expression in MCF7 cells, whereas it suppressed expression of these proteins in BT20 cells. Cell survival was decreased after inecalcitol treatment either alone or combined in MCF7 cells. Interestingly, the combination therapy upregulated mitochondrial ROS and mitotracker staining in both cell lines. Furthermore, in vivo validation in a MCF7 cell line-derived xenograft mouse model decreased tumor growth and cell cycle progression after combination therapy, but not in a TNBC BT20 cell line-derived xenograft model. In conclusion, we show that addition of a potent vitamin D3 analog to selective CDK4/6 inhibitor treatment results in increased antiproliferative effects in ER+ BC both in vitro and in vivo. [ABSTRACT FROM AUTHOR]

Highlights • WY 1048 is a novel 1,25(OH) 2 D 3 analog with bone protective properties. • WY 1048 in combination with risedronate restores ovariectomy-induced bone loss. • WY 1048 restores bone loss to a greater extent than 1,25(OH) 2 D 3. • Bone loss is restored without causing hypercalcemia or hypercalciuria. Abstract Bisphosphonates like risedronate inhibit osteoclast-mediated bone resorption and are therefore used in the prevention and treatment of osteoporosis. Also vitamin D 3 and calcium supplementation is commonly used in the prevention or treatment of osteoporosis. Combined therapy of risedronate with 1,25(OH) 2 D 3 , the active metabolite of vitamin D 3 , may be advantageous over the use of either monotherapy, but bears a risk of causing hypercalcemia thereby decreasing the therapeutic window for osteoporosis treatment. In this study, we evaluated the effect on bone mass of the combination of risedronate with the 17-methyl 19-nor five-membered D-ring vitamin D 3 analog WY 1048 in a mouse ovariectomy model for postmenopausal osteoporosis. Ovariectomy-induced bone loss was restored by administration of risedronate or a combination of risedronate with 1,25(OH) 2 D 3. However, the combination of WY 1048 with risedronate induced an even higher increase on total body and spine bone mineral density and on trabecular and cortical bone mass. Our data indicate that combination therapy of risedronate with WY 1048 was superior in restoring and improving bone mass over a combination of risedronate with 1,25(OH) 2 D 3 with minimal calcemic side effects. [ABSTRACT FROM AUTHOR]