Comparative regulation of gene expression by 1,25-dihydroxyvitamin D3 in cells derived from normal mammary tissue and breast cancer

Abstract

Previous genomic profiling of immortalized, non-tumorigenic human breast epithelial cells identified a set of 1,25-dihydroxyvitamin D3 (1,25D) regulated genes with potential relevance to breast cancer prevention. In this report, we characterized the effect of 1,25D on a subset of these genes in six cell lines derived from mammary tissue and breast cancers. Non-tumorigenic cell lines included hTERT-HME1, HME and MCF10A cells which are often used to model normal breast epithelial cells. Breast cancer cell lines included MCF7 cells (a model of early stage, estrogen-dependent disease), DCIS.com cells (a derivative of MCF10A cells that models in situ breast cancer) and Hs578T cells (a model of metastatic disease). All of these cell lines express the vitamin D receptor (VDR) and exhibit anti-cancer responses to 1,25D such as changes in proliferation, apoptosis, metabolism, or invasion. Our comparative data demonstrate highly variable responses to 1,25D (100nM, 24h) between the cell lines. In both hTERT-HME1 and HME cell lines, CYP24A1, SLC1A1 and ITGB3 were up-regulated whereas KDR, GLUL and BIRC3 were down-regulated in response to 1,25D. In contrast, no changes in SLC1A1, ITGB3 or GLUL expression were detected in 1,25D treated MCF10A cells although KDR and BIRC3 were down-regulated by 1,25D. The effects of 1,25D on these genes in the breast cancer cell lines were blunted, with the DCIS.com cells exhibiting the most similar responses to the immortalized hTERT-HME1 and HME cells. The differences in cellular responses were not due to general impairment in VDR function as robust CYP24A1 induction was observed in all cell lines. Thus, our data indicate that the genomic changes induced by 1,25D are highly cell-type specific even in model cell lines derived from the same tissue. The implication of these findings is that genomic responses to changes in vitamin D status in vivo are likely to be distinct from individual to individual, particularly in neoplastic tissue. This article is part of a Special Issue entitled '17th Vitamin D Workshop'.

Keywords: Genomics; Mammary gland; Vitamin D.

Figure 1. Relative VDR expression in vehicle and 1,25D treated breast cells

VDR mRNA was quantitated by qPCR in hTERT-HME1, HME, MCF10A, MCF7, DCIS.com, and Hs578T cells treated with 100nM 1,25D or ethanol vehicle for 24h. Data were calculated by the ΔΔCt method, normalized against 18S and expressed relative to those of the hTERT-HME1 cell line which was set to 1. Bars represent mean ± standard deviation of triplicates. A. Basal VDR expression. * Significantly different from hTERT-HME1 value by one-way ANOVA, p<0.05 B. 1,25D treatment. * Significantly different, 1,25D treated vs. control within each cell line.

Figure 2. Relative CYP24A1 expression in vehicle and 1,25D treated breast cells

CYP24A1 mRNA was quantitated by qPCR in hTERT-HME1, HME, MCF10A, MCF7, DCIS.com, and Hs578T cells treated with 100nM 1,25D or ethanol vehicle for 24h. Data were calculated by the ΔΔCt method, normalized against 18S and expressed relative to those of the hTERT-HME1 cell line which was set to 1. Bars represent mean ± standard deviation of triplicates. A. Basal CYP24A1 expression. * Significantly different from hTERT-HME1 value by one-way ANOVA, p<0.05 B. 1,25D treatment. Fold increase with 1,25D treatment within each cell line is indicated above bars. All 1,25D treated values were significantly different from vehicle control values.