Abstract
1,25-Dihydroxyvitamin D3 (1,25D3) induces growth arrest and apoptosis in breast cancer cells in vivo and in vitro, however the exact mechanisms are unclear. Although the vitamin D receptor (VDR), a ligand dependent transcription factor, is required for growth regulation by vitamin D, the specific target genes that trigger these effects are unknown. Genomic profiling of murine mammary tumor cells with differential VDR expression identified 35 transcripts that were altered by the 1,25D3-VDR complex including Hyaluronan Synthase-2 (Has2). Here we confirmed that 1,25D3 reduces both HAS2 gene expression and hyaluronic acid (HA) synthesis in multiple models of breast cancer. Furthermore, we show that the growth inhibitory effects of 1,25D3 are partially reversed in the presence of high molecular weight HA. HAS2 expression and HA production are elevated in immortalized human mammary epithelial cells induced to undergo epithelial-mesenchymal transition (EMT) through stable expression of TGFβ, SNAIL or TWIST and in those expressing oncogenic H-RASV12, indicating that deregulation of HA production may be an early and frequent event in breast tumorigenesis. 1,25D3 also reduces HA secretion and acts additively with an HA synthesis inhibitor to slow growth of cells expressing TGFβ, SNAIL and TWIST. Analysis of mammary gland and tumors from Vdr knockout mice suggest that loss of VDR is associated with enhanced HAS2 expression and HA production in vivo. These data define a novel role for 1,25D3 and the VDR in control of HA synthesis in epithelial tissues that likely contributes to its anti-cancer actions.
Highlights
1,25-Dihydroxyvitamin D3 (1,25D3), the high affinity ligand for the nuclear vitamin D receptor (VDR), regulates multiple cancer processes in vivo and in vitro, the specific gene targets and mechanisms that mediate these effects are unclear
In previous studies we demonstrated that 1,25D3 down-regulated mRNA expression of the hyaluronic acid (HA) synthesizing enzyme Hyaluronan Synthase-2 (Has2) in a VDR-dependent manner after 24 hours [4]
1,25D3 reduced Has2 expression at all time points tested in WT145 cells and in KOhVDR cells (KO240 cells engineered to ectopically express human VDR)
Summary
1,25-Dihydroxyvitamin D3 (1,25D3), the high affinity ligand for the nuclear VDR, regulates multiple cancer processes (cell cycle, apoptosis, migration, invasion) in vivo and in vitro, the specific gene targets and mechanisms that mediate these effects are unclear. We previously established invasive mammary tumor cell lines from wild-type (WT) and VDR knockout (KO) mice and demonstrated that the VDR is necessary for 1,25D3 mediated anti-cancer signaling in vitro and in vivo [1,2,3] Genomic profiling in this model system [4, 5] identified 35 transcripts that were altered by the 1,25D3VDR complex, only four of which were down-regulated. HAS2 and HA promote epithelial-mesenchymal transition (EMT), survival, invasion and metastasis in vitro and in vivo [14,15,16,17,18,19,20,21] Many of these effects result from HA-mediated activation of CD44, a pro-survival receptor enriched on the surface of cancer stem cells [17, 22,23,24,25,26]. In the studies reported here we assessed whether 1,25D3 regulates HAS2 in cellular models of human breast cancer, and whether suppression of HAS2 by 1,25D3 is sufficient to inhibit HA synthesis in the context of aggressive disease
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
