Activation of pro-survival metabolic networks by 1,25(OH)2D3 does not hamper the sensitivity of breast cancer cells to chemotherapeutics

Abstract

BackgroundWe have previously identified 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], the bioactive form of vitamin D3, as a potent regulator of energy-utilization and nutrient-sensing pathways in prostate cancer cells. In the current study, we investigated the effects of 1,25(OH)2D3 on breast cancer (BCa) cell metabolism using cell lines representing distinct molecular subtypes, luminal (MCF-7 and T-47D), and triple-negative BCa (MDA-MB-231, MDA-MB-468, and HCC-1143).Methods1,25(OH)2D3’s effect on BCa cell metabolism was evaluated by employing a combination of real-time measurements of glycolysis/oxygen consumption rates using a biosensor chip system, GC/MS-based metabolomics, gene expression analysis, and assessment of overall energy levels. The influence of treatment on energy-related signaling molecules was investigated by immunoblotting.ResultsWe show that 1,25(OH)2D3 significantly induces the expression and activity of the pentose phosphate pathway enzyme glucose-6-phosphate dehydrogenase (G6PD) in all BCa cell lines, however differentially influences glycolytic and respiratory rates in the same cells. Although 1,25(OH)2D3 treatment was found to induce seemingly anti-oxidant responses in MCF-7 cells, such as increased intracellular serine levels, and reduce the expression of its putative target gene thioredoxin-interacting protein (TXNIP), intracellular reactive oxygen species levels were found to be elevated. Serine accumulation in 1,25(OH)2D3-treated cells was not found to hamper the efficacy of chemotherapeutics, including 5-fluorouracil. Detailed analyses of the nature of TXNIP’s regulation by 1,25(OH)2D3 included genetic and pharmacological inhibition of signaling molecules and metabolic enzymes including AMP-activated protein kinase and G6PD, as well as by studying the ITCH (E3 ubiquitin ligase)-TXNIP interaction. While these investigations demonstrated minimal involvement of such pathways in the observed non-canonical regulation of TXNIP, inhibition of estrogen receptor (ER) signaling by tamoxifen mirrored the reduction of TXNIP levels by 1,25(OH)2D3, demonstrating that the latter’s negative regulation of ER expression is a potential mechanism of TXNIP modulation.ConclusionsAltogether, we propose that regulation of energy metabolism contributes to 1,25(OH)2D3’s anti-cancer effects and that combining 1,25(OH)2D3 with drugs targeting metabolic networks in tumor cells may lead to synergistic effects.Electronic supplementary materialThe online version of this article (10.1186/s40170-018-0183-6) contains supplementary material, which is available to authorized users.

1,25-hydroxyvitamin D3 decreases endoplasmic reticulum stress-induced inflammatory response in mammary epithelial cells

“…At these concentrations of TG and TM, ER stress was clearly induced but cell viability was only moderately impaired thus enabling us to avoid strong bias of impaired cell viability on cellular effects caused by ER stress. Treatment of MCF-7 cells with 1,25D 3 alone at a wide concentration range (1 to 500 nmol/L), which has been shown to exert biological effects in other cell culture studies [35], for 24 h did not impair cell viability compared to vehicle control cells (Fig 2A). Thus, the effect of 1,25D 3 on ER stress signaling induced by TG and TM was studied at a low (10 nmol/L) and a high (100 nmol/L) concentration.…”

Pharmacological activation of pyruvate kinase M2 reprograms glycolysis leading to TXNIP depletion and AMPK activation in breast cancer cells

“…Cells were cultured as described before [ 26 ] until they are 60–70% confluent, subsequently treated with DASA-58 (15 μM), and lysed at the indicated time point. Cells were collected washed with PBS and re-suspended in ice-cold lysis buffer (KCl, MgCl2, HEPES, EDTA).…”

Vitamin D in Triple-Negative and BRCA1-Deficient Breast Cancer—Implications for Pathogenesis and Therapy

“…It was observed that 1,25(OH)2D induced the expression and increased activity of glucose-6-phosphate dehydrogenase (G6PD), an enzyme of the pentose phosphate pathway in the TNBC MDA-MB-231, MDA-MB-468, and HCC-1143 cell lines [71]. 1,25(OH)2D reduced respiration in all these TNBC cell lines and increased citrate levels and ATP production in MDA-MB-231 cells.…”