A Role for Interleukin-1 Alpha in the 1,25 Dihydroxyvitamin D3 Response in Mammary Epithelial Cells

Sophia L Maund,Lihong Shi,Scott D Cramer,Andrzej T Slominski

doi:10.1371/journal.pone.0081367

Sophia L Maund, Lihong Shi + Show 2 more

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https://doi.org/10.1371/journal.pone.0081367

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Abstract

Breast cancer is the most common non-cutaneous malignancy in American women, and better preventative strategies are needed. Epidemiological and laboratory studies point to vitamin D3 as a promising chemopreventative agent for breast cancer. Vitamin D3 metabolites induce anti-proliferative effects in breast cancer cells in vitro and in vivo, but few studies have investigated their effects in normal mammary epithelial cells. We hypothesized that 1,25(OH)2D3, the metabolically active form of vitamin D3, is growth suppressive in normal mouse mammary epithelial cells. In addition, we have previously established a role for the cytokine interleukin-1 alpha (IL1α) in the anti-proliferative effects of 1,25(OH)2D3 in normal prostate cells, and so we hypothesized that IL1α is involved in the 1,25(OH)2D3 response in mammary cells. Evaluation of cell viability, clonogenicity, senescence, and induction of cell cycle regulators p21 and p27 supported an anti-proliferative role for 1,25(OH)2D3 in mammary epithelial cells. Furthermore, 1,25(OH)2D3 increased the intracellular expression of IL1α, which was necessary for the anti-proliferative effects of 1,25(OH)2D3 in mammary cells. Together, these findings support the chemopreventative potential of vitamin D3 in the mammary gland and present a role for IL1α in regulation of mammary cell proliferation by 1,25(OH)2D3.

Highlights

Epidemiological and laboratory studies point to vitamin D3 as a promising chemopreventative agent for breast cancer [1,2,3,4,5,6,7]
To test whether IL1α is a target of 1,25(OH)2D3 in mammary cells as well, we investigated its regulation in mammary epithelial cells (MMECs) in response to 1,25(OH)2D3. Quantitative real-time PCR analysis (qPCR) data showed a 6-fold increase in IL1α mRNA by 24 hrs of exposure to 1,25(OH)2D3, which was sustained at 48 hr (Figure 4A)
We previously identified a putative vitamin D response element (VDRE) in the promoter region of IL1α that aligns with established VDREs in other targets of 1,25(OH)2D3 [21], so it is possible that IL1α is a direct transcriptional target of 1,25(OH)2D3

Summary

Introduction

Epidemiological and laboratory studies point to vitamin D3 as a promising chemopreventative agent for breast cancer [1,2,3,4,5,6,7]. Low serum 25(OH)D3 concentrations are correlated with an increased risk for breast cancer [3], and suboptimal serum 25(OH)D3 levels are associated with more aggressive breast tumors, worse prognostic markers, and a higher risk for breast cancer recurrence [12] These findings support reports of increased breast cancer risk and decreased survival in patients deficient in vitamin D3, and they warrant further investigations into the specific contributions of vitamin D3 to breast health. CYP27B1 (which encodes the 1,25(OH)2D3 activating enzyme 1α-OHase) expression is slightly lower in invasive breast tumors, while CYP24A1 (which encodes the 1,25(OH)2D3 inactivating enzyme 24-hydroxylase) levels are increased in tumors compared to benign lesions [18]. These studies suggest that breast cancer is associated with deregulation of vitamin D3 signaling. We report that 1,25(OH)2D3 induces IL1α expression in normal mouse mammary epithelial cells (MMECs), and that IL1α contributes to the antiproliferative effects of 1,25(OH)2D3 in these cells

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