Abstract 3742: Vitamin D inhibits hyaluronan synthesis and extracellular matrix gene expression in triple negative breast cancer
Authors: Narvaez Carmen J. , Balinth Seamus , Welsh JoEllen 
Published: August 2018

Abstract
Human breast tumors with abundant hyaluronan (HA) and high expression of the HA synthesizing enzyme HAS2 are aggressive and exhibit poorer survival than tumors with low HA/HAS2. The vitamin D receptor (VDR) and its ligand 1,25(OH)2D3 (1,25D) exert anti-tumor effects in cancer cells and inhibit breast cancer growth in animals, but considerable heterogeneity has been reported in different model systems. Genomic profiling has demonstrated that, while a few genes are commonly regulated by 1,25D in all VDR positive cell lines, the majority of VDR regulated genes are cell line specific. In general, cell lines derived from the more aggressive tumor subtypes such as Triple Negative Breast Cancer (TNBC) express low levels of VDR and are less sensitive to 1,25D than cell lines derived from less aggressive subtypes. Through genomic profiling of TNBC cells derived from wild-type (WT) and VDR knockout (VDRKO) mice, we identified HAS2 as a 1,25D repressed gene. To understand the mechanistic impact of vitamin D and Has2 on HA synthesis and tumorigenic potential in TNBC cells, we utilized the human TNBC cell line Hs578T, which is representative of the mesenchymal/stem-like (MSL) subtype of TNBC. 1,25D inhibited HAS2 expression and HA synthesis in Hs578T cells, and also down-regulated CD44, a breast cancer stem cell marker which acts as the receptor for HA, the product of HAS2. Further studies determined that Hs578T cells are heterogeneous with respect to morphology and HAS2 expression. We therefore sorted parental Hs578T cells into HAhigh and HAlow populations. HAhigh populations exhibited elevated HA production, smaller size, increased proliferation and higher motility than HAlow populations. Through genomic profiling, HAhigh populations demonstrated higher levels of expression of genes involved in the enzymatic production and degradation of HA (HAS2, HAS2-AS, HYAL1), expression of extracellular matrix (ECM) proteins involved in HA binding and motility (PTX3, CEMIP, ACAN) and epithelial-mesenchymal transition (SNAI1) compared to HAlow populations. Despite their more aggressive phenotype, HAhigh populations retained expression of VDR protein at levels comparable to that of parental Hs578T cells and HAlow subclones. Treatment with 1,25D decreased production of HA in both HAhigh and HAlow populations, but significantly reduced expression of genes involved in the production of HA (HAS2, HAS2-AS) and HA binding and motility (ACAN, CEMIP) only in the HAhigh populations. This study suggests that 1,25D/VDR can suppress HAS2 and HA production and signaling in the ECM, and thus may reduce the aggressive phenotype of TNBC.
Citation Format: Carmen J. Narvaez, Seamus Balinth, JoEllen Welsh. Vitamin D inhibits hyaluronan synthesis and extracellular matrix gene expression in triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3742.