Effects of sodium butyrate on expression of members of the IGF-binding protein superfamily in human mammary epithelial cells

Abstract

Dietary factors play an important role in both the development and prevention of human cancers, including breast carcinoma. One dietary micronutrient, sodium butyrate (NaB), is a major end product of dietary starch and fiber, produced naturally during digestion by anaerobic bacteria in the cecum and colon. NaB is a potent growth inhibitor and initiates cell differentiation for many cell types in vitro. In this study, we investigated the effects of NaB on three human mammary epithelial cells and regulation of the IGF axis, specifically, IGF-binding protein-3 (IGFBP-3), a known growth regulator in human mammary cells, and IGFBP-related protein 2 (IGFBP-rP2)/connective tissue growth factor. NaB inhibited DNA synthesis, as measured by [ 3 H]thymidine incorporation, in estrogen-responsive (MCF-7) and estrogen-non-responsive (Hs578T) breast cancer cells, and normal human mammary epithelial cells (HMEC) to a similar degree (up to 90% inhibition at 1-10 mM concentrations). Treatment of cells with NaB induced histone hyperacetylation, suggesting that NaB exerts its biological effects, at least in part, as a histone deacetylase inhibitor in mammary epithelial cells. Treatment of Hs578T cells with NaB caused an induction of apoptotic cell death. NaB treatment resulted in increased levels of p21Waf1/Cip1 mRNA and protein in Hs578T cells and distinct upregulation of p27 Kip1 in HMEC, suggesting that NaB activates different genes involved in cell cycle arrest, depending upon the cell type. In the same context, among the IGFBP superfamily members tested, NaB specifically upregulated the expression of IGFBP-3 and IGFBP-rP2. These two proteins are known to be involved in inhibition of mammary epithelial cell replication. Northern blot analysis showed that NaB treatment at 1-10 mM concentrations caused a dose-dependent stimulation of IGFBP-3 mRNA expression in cancerous cells and IGFBP-rP2 mRNA expression in both cancerous and non-cancerous cells. Protein data from Western ligand blot and immunoblot analyses demonstrated parallel results.In summary, we have demonstrated that NaB (i) uniformly suppresses DNA synthesis in both cancerous and non-cancerous mammary cells, and (ii) upregulates IGFBP-3 and IGFBP-rP2 mRNA and protein levels in cancerous and non-cancerous mammary cells. These results provide the first demonstration that butyrate regulates the IGFBP system in the human mammary system.

Reduced Expression of <i>GNA11</i> and Silencing of <i>MCT1</i> in Human Breast Cancers

“…MCT1 is known as a cellular transporter of monocarboxylates, including butyrate [32, 33]. Since butyrate plays important roles in the differentiation of mammary epithelial cells [34, 35], the downregulation of its transporter could confer a growth advantage to mammary epithelial cells.…”

Effects of Na-butyrate supplementation in milk formula on plasma concentrations of GH and insulin, and on rumen papilla development in calves

“…In these last conditions, the actions of butyrate are believed to involve the hormononeuro-immunosystem (Guilloteau et al 2010a). As examples, it was suggested that Na-butyrate may act through growth factors (Tsubaki et al 2001) or endocrine systems (Simon et al 1997, Bartholome et al 2004, Katoh et al 2007). Na-butyrate may also stimulate defence systems through heat shock proteins and modify immune and inflammatory responses (Ren et al 2001, Millard et al 2002, Böcker et al 2003).…”

Is Na-butyrate a growth factor in the preruminant calf? Preliminary results

“…Moreover, in rats, Na-butyrate infusion into the lumen of the large intestine stimulated the mucin secretion (Barcelo et al, 2000). Finally, it was shown that Na-Butyrate is implicated in gene expression (Tsubaki et al, 2001;Böker et al, 2003).…”