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

Diagnostic Aspects of Vitamin D: Clinical Utility of Vitamin D Metabolite Profiling

The assay of vitamin D that began in the 1970s with the quantification of one or two metabolites, 25‐OH‐D or 1,25‐(OH)₂D, continues to evolve with the emergence of liquid chromatography tandem mass spectrometry (LC‐MS/MS) as the technique of choice. This highly accurate, specific, and sensitive technique has been adopted by many fields of endocrinology for the measurement of multiple other components of the metabolome, and its advantage is that it not only makes it feasible to assay 25‐OH‐D or 1,25‐(OH)₂D but also other circulating vitamin D metabolites in the vitamin D metabolome. In the process, this broadens the spectrum of vitamin D metabolites, which the clinician can use to evaluate the many complex genetic and acquired diseases of calcium and phosphate homeostasis involving vitamin D. Several examples are provided in this review that additional metabolites (eg, 24,25‐(OH)₂D₃, 25‐OH‐D₃‐26,23‐lactone, and 1,24,25‐(OH)₃D₃) or their ratios with the main forms offer valuable additional diagnostic information. This approach illustrates that biomarkers of disease can also include metabolites devoid of biological activity. Herein, a case is presented that the decision to switch to a LC‐MS/MS technology permits the measurement of a larger number of vitamin D metabolites simultaneously and does not need to lead to a dramatic increase in cost or complexity because the technique uses a highly versatile tandem mass spectrometer with plenty of reserve analytical capacity. Physicians are encouraged to consider adding this rapidly evolving technique aimed at evaluating the wider vitamin D metabolome toward streamlining their approach to calcium‐ and phosphate‐related disease states. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Vitamin D and Breast Cancer: Mechanistic Update

The presence of the vitamin D receptor (VDR) in mammary gland and breast cancer has long been recognized, and multiple preclinical studies have demonstrated that its ligand, 1,25-dihydroxyvitamin D (1,25D), modulates normal mammary gland development and inhibits growth of breast tumors in animal models. Vitamin D deficiency is common in breast cancer patients, and some evidence suggests that low vitamin D status enhances the risk for disease development or progression. Although many 1,25D-responsive targets in normal mammary cells and in breast cancers have been identified, validation of specific targets that regulate cell cycle, apoptosis, autophagy, and differentiation, particularly in vivo, has been challenging. Model systems of carcinogenesis have provided evidence that both VDR expression and 1,25D actions change with transformation, but clinical data regarding vitamin D responsiveness of established tumors is limited and inconclusive. Because breast cancer is heterogeneous, the relevant VDR targets and potential sensitivity to vitamin D repletion or supplementation will likely differ between patient populations. Detailed analysis of VDR actions in specific molecular subtypes of the disease will be necessary to clarify the conflicting data. Genomic, proteomic, and metabolomic analyses of in vitro and in vivo model systems are also warranted to comprehensively understand the network of vitamin D-regulated pathways in the context of breast cancer heterogeneity. This review provides an update on recent studies spanning the spectrum of mechanistic (cell/molecular), preclinical (animal models), and translational work on the role of vitamin D in breast cancer. © 2021 The Author. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Vitamin D receptor (VDR) and metabolizing enzymes CYP27B1 and CYP24A1 in breast cancer

Vitamin D Receptor (VDR), a nuclear steroid receptor, is a transcription factor with a primary physiologic role in calcium metabolism. It has also a physiologic role in breast tissues during development of the gland and postpartum. In addition, it is commonly expressed in breast cancer and has tumor suppressive effects. Cytochrome enzymes CYP27B1 and CYP24A1 that perform the final conversion of the circulating form of vitamin D, 25-hydroxyvitamin D (25-OHD) to the active VDR ligand, 1a,25-dihydroxyvitamin D and the catabolism of it to inactive 24,25-dihydroxyvitamin D, respectively, are also expressed in breast cancer tissues. Defective regulation of the receptor and the metabolic enzymes of VDR ligand is prevalent in breast cancer and leads to decreased VDR signaling. The expression and molecular defects of VDR, CYP27B1 and CYP24A1 that perturb physiologic function, the implications for breast cancer progression and therapeutic opportunities are discussed in this paper.

1,25-Dihydroxyvitamin D Regulation of Glutamine Synthetase and Glutamine Metabolism in Human Mammary Epithelial Cells

Genomic profiling has identified a subset of metabolic genes that are altered by 1,25-dihydroxyvitamin D (1,25D) in breast cells, including GLUL, the gene that encodes glutamine synthetase (GS). In this study, we explored the relevance of vitamin D modulation of GLUL and other metabolic genes in the context of glutamine utilization and dependence. We show that exposure of breast epithelial cells to glutamine deprivation or a GS inhibitor reduced growth and these effects were exacerbated by cotreatment with 1,25D. 1,25D downregulation of GLUL was sufficient to reduce abundance and activity of GS. Flow cytometry demonstrated that glutamine deprivation induced S phase arrest, likely due to reduced availability of glutamine for DNA synthesis. In contrast, 1,25D induced G0/G1 arrest, indicating that its effects are not solely due to reduced glutamine synthesis. Indeed, 1,25D also reduced expression of GLS1 and GLS2 genes, which code for glutaminases that shunt glutamine into the tricarboxylic acid (TCA) cycle. Consistent with reduced entry of glutamine into the TCA cycle, 1,25D inhibited glutamine oxidation and the metabolic response to exogenous glutamine as analyzed by Seahorse Bioscience extracellular flux assays. Effects of 1,25D on GLUL/GS expression and glutamine oxidation were retained in human mammary epithelial (HME) cells that express SV-40 (HME-LT cells) but not in those that express SV-40 and oncogenic H-Ras (HME-PR cells). Furthermore, HME-PR cells exhibited glutamine independence and expressed constitutively high levels of GLUL/GS, which were unaffected by 1,25D. Collectively, these data suggest that 1,25D alters glutamine availability, dependence, and metabolism in nontransformed and preneoplastic mammary epithelial cells in association with cell cycle arrest.

Function of the vitamin D endocrine system in mammary gland and breast cancer

The nuclear receptor for 1α,25-dihydroxycholecalciferol (1,25D), the active form of vitamin D, has anti-tumor actions in many tissues. The vitamin D receptor (VDR) is expressed in normal mammary gland and in many human breast cancers suggesting it may represent an important tumor suppressor gene in this tissue. When activated by 1,25D, VDR modulates multiple cellular pathways including those related to energy metabolism, terminal differentiation and inflammation. There is compelling pre-clinical evidence that alterations in vitamin D status affect breast cancer development and progression, while clinical and epidemiological data are suggestive but not entirely consistent. The demonstration that breast cells express CYP27B1 (which converts the precursor vitamin D metabolite 25D to the active metabolite 1,25D) and CYP24A1 (which degrades both 25D and 1,25D) provides insight into the difficulties inherent in using dietary vitamin D, sun exposure and/or serum biomarkers of vitamin D status to predict disease outcomes. Emerging evidence suggests that the normally tight balance between CYP27B1 and CYP24A1 becomes deregulated during cancer development, leading to abrogation of the tumor suppressive effects triggered by VDR. Research aimed at understanding the mechanisms that govern uptake, storage, metabolism and actions of vitamin D steroids in normal and neoplastic breast tissue remain an urgent priority.

Combined calcitriol and menadione reduces experimental murine triple negative breast tumor

BACKGROUND

Calcitriol (D) or 1,25(OH)₂D₃ inhibits the growth of several tumor cells including breast cancer cells, by activating cell death pathways. Menadione (MEN), a glutathione-depleting compound, may be used to potentiate the antiproliferative actions of D on cancer cells. We have previously shown in vitro that MEN improved D-induced growth arrest on breast cancer cell lines, inducing oxidative stress and DNA damage via ROS generation. Treatment with MEN+D resulted more effective than D or MEN alone.

OBJECTIVE

To study the in vivo effect of calcitriol, MEN or their combination on the development of murine transplantable triple negative breast tumor M-406 in its syngeneic host.

METHODS

Tumor M-406 was inoculated s.c., and when tumors reached the desired size, animals were randomly assigned to one of four groups receiving daily i.p. injections of either sterile saline solution (controls, C), MEN, D, or both (MEN+D). Body weight and tumor volume were recorded three times a week. Serum calcium was determined before and at the end of the treatment, at which time tumor samples were obtained for histological examination.

RESULTS

None of the drugs, alone or in combination, affected mice body weight in the period studied. The combined treatment reduced tumor growth rate (C vs. MEN+D, P<0.05) and the corresponding histological sections exhibited small remaining areas of viable tumor only in the periphery. A concomitant DNA fragmentation was observed in all treated groups and MEN potentiated the calcitriol effect on tumor growth.

CONCLUSIONS

As previously observed in vitro, treatment with MEN and D delayed tumor growth in vivo more efficiently than the individual drugs, with evident signals of apoptosis induction. Our results propose an alternative protocol to treat triple negative breast cancer, using GSH depleting drugs together with calcitriol, which would allow lower doses of the steroid to maintain the antitumor effect while diminishing its adverse pharmacological effects.

Association between Serum 25-hydroxy Vitamin D Concentration and TaqI Vitamin D Receptor Gene Polymorphism among Jordanian Females with Breast Cancer

BACKGROUND

Breast cancer is the most common type of cancer among females. Genetic polymorphisms might have a role in carcinogenesis. The aim of this study was to determine whether C to T base substitution within TaqI Vitamin D receptor (VDR) gene (rs731236) in exon 9 was a risk factor among patients with breast cancer.

METHODS

Peripheral blood was drawn from 122 Jordanian breast cancer patients and 100 healthy Jordanian volunteers in Al-Basheer Hospital during the summer months (from June to November of 2013, 2014, and 2015). DNA was amplified using polymerase chain reaction (PCR), followed by TaqI restriction enzyme digestion. Quantification of serum 25-hydroxy Vitamin D (25[OH]D) level was determined by competitive immunoassay Elecsys.

RESULTS

Genotypic frequencies for TaqI TT, Tt, and tt genotypes were 41%, 46%, and 13% for breast cancer compared to 42%, 50%, and 8% for control, respectively. Vitamin D serum level was significantly lower in the breast cancer patients (8.1 ± 0.3 ng/ml) compared to the control group (21.2 ± 0.6 ng/ml; P= 0.001). This study showed an inverse association between 25(OH)D serum level and breast cancer risk (odds ratio [OR], 22.72, 95% confidence interval [CI], 10.06-51.29).

CONCLUSIONS

An inverse association was found between 25(OH)D serum level and breast cancer risk. Statistical difference was also found between different VDR TaqI genotypes and circulating levels of 25(OH)D among Jordanian females with breast cancer.

Effects of vitamin D and its metabolites on cell viability and Staphylococcus aureus invasion into bovine mammary epithelial cells

Vitamin D has been found have various biological effects that may be potent in preventing bovine mastitis. Two forms of vitamin D, vitamin D₂ (D₂) and vitamin D₃ (D₃), can be hydroxylated to functional metabolites in cattle. The objectives of the present study were to investigate the potential of vitamin D compounds for controlling bovine mastitis using in vitro cell models, and to compare the differences between D₂ and D₃ compounds. Results showed that D₂ compounds have comparable effects to their D₃ analogues on inhibiting MAC-T cell viability in vitro. S. aureus growth was inhibited by high concentrations of D₂, D₃, 25(OH)D₂ and 25(OH)D₃. 25(OH)D₂ and 25(OH)D₃ induced CYP24A1 expression but reduced VDR mRNA expression, whereas the expression of CYP27B1, occludin, and E-cadherin did not change. Additionally, the induction of CYP24A1 expression by 25(OH)D₃ was higher than that of 25(OH)D₂, which may contribute to their differences in inhibiting cell viability. S. aureus invaded into MAC-T cells and universally inhibited gene expressions. Pre-treat MAC-T cells with 25(OH)D₂ reduced S. aureus adhesion while pre-treatment with 25(OH)D₃ inhibited S. aureus invasion, but neither of the compounds attenuated the S. aureus-induced gene expression reduction. In conclusion, the present study shows that D₂ compounds have comparable effects on inhibiting cell viability and S. aureus invasion to their D₃ analogues in vitro, suggesting that D₂ and its metabolites have potential in controlling bovine mastitis.

Identification of vitamin D3 target genes in human breast cancer tissue

Multiple epidemiological studies have shown that high vitamin D₃ status is strongly associated with improved breast cancer survival. To determine the molecular pathways influenced by 1 alpha, 25-dihydroxyvitamin D₃ (1,25D) in breast epithelial cells we isolated RNA from normal human breast and cancer tissues treated with 1,25D in an ex vivo explant system. RNA-Seq revealed 523 genes that were differentially expressed in breast cancer tissues in response to 1,25D treatment, and 127 genes with altered expression in normal breast tissues. GoSeq KEGG pathway analysis revealed 1,25D down-regulated cellular metabolic pathways and enriched pathways involved with intercellular adhesion. The highly 1,25D up-regulated target genes CLMN, SERPINB1, EFTUD1, and KLK6were selected for further analysis and up-regulation by 1,25D was confirmed by qRT-PCR analysis in breast cancer cell lines and in a subset of human clinical samples from normal and cancer breast tissues. Ketoconazole potentiated 1,25D-mediated induction of CLMN, SERPINB1, and KLK6 mRNA through inhibition of 24-hydroxylase (CYP24A1) activity. Elevated expression levels of CLMN, SERPINB1, and KLK6 are associated with prolonged relapse-free survival for breast cancer patients. The major finding of the present study is that exposure of both normal and malignant breast tissue to 1,25D results in changes in cellular adhesion, metabolic pathways and tumor suppressor-like pathways, which support epidemiological data suggesting that adequate vitamin D₃ levels may improve breast cancer outcome.

Evaluation of Serum Vitamin D Levels in Adolescents with Pubertal Gynecomastia

BACKGROUND

Since vitamin D has an inhibitory function on ductal morphogenesis of the pubertal mammary gland, it may have a role in the development of gynecomastia. The aim of this study was to determine the effect of vitamin D deficiency on the development of pubertal gynecomastia.

METHODS

Serum 25-hydroxyvitamin D (25D) levels in 50 adolescents with pubertal gynecomastia and 54 healthy controls between the ages of 11 and 17 years were compared.

RESULTS

Mean 25D level was 14.03 ± 6.38 (5.0-32.5) ng/ml in the pubertal gynecomastia group and 15.19 ± 6.49 (5.0-33.2) ng/ml in the control group (p = 0.361). According to the vitamin D status classification of the American Academy of Pediatrics, 66% of the pubertal gynecomastia group was found to be deficient and 14% were insufficient. In the control group these values were 53.7% and 29.6%, respectively (p = 0.158).

CONCLUSION

From our results we hypothesize that, rather than low serum levels of 25D, a dysregulation of the vitamin D signal pathway, vitamin D metabolism or vitamin D storage within the mammary tissue might be the contributing factors to the development of gynecomastia.

PADI2 gene confers susceptibility to breast cancer and plays tumorigenic role via ACSL4, BINC3 and CA9 signaling

BACKGROUND

Peptidylarginine deiminase (PAD) post-translationally converts arginine residues to citrulline residues. Recent studies have suggested that PADI2 (PAD isoform 2), a member of the PAD family, is involved in the tumorigenic process of some tumors, especially breast cancer. However, little is known about the mechanisms of PADI2 in tumorigenesis. This study aimed to elucidate the tumorigenic role and regulatory pathway of PADI2 in breast tumors.

METHODS

The Sequenom MassARRAY and TaqMan genotyping methods were used to investigate the correlation between PADI2 gene SNPs and various tumor risks. PCR array analyses, including cancer pathway finder and signal transduction PCR arrays, were performed to investigate the tumorigenic pathway of PADI2 in the MCF-7 breast cancer cell line following treatment with anti-PADI2 siRNA. Cell proliferation, apoptosis and transwell migration assays were performed to observe the effect of PADI2 in MCF-7 cells treated with anti-PADI2 siRNA.

RESULTS

Both Sequenom MassARRAY and TaqMan genotyping assays demonstrated that SNP rs10788656 in the PADI2 gene was significantly associated with breast cancer. PCR arrays indicated that inhibiting PADI2 expression significantly increased expression of CA9 and decreased expression of ACSL4 and BIRC3 in MCF-7 cells, which was verified using real-time PCR. Inhibiting PADI2 expression also significantly decreased the migration ability of MCF-7 cells but did not affect cell proliferation or apoptosis.

CONCLUSIONS

The PADI2 gene confers susceptibility to breast cancer. PADI2 expression contributes to abnormal migration of breast tumor cells. PADI2 affects tumorigenesis in breast tumor cells by regulating the expression of ACSL4, BINC3 and CA9, which are known to promote abnormal lipid metabolism and cell invasion of tumors.

The role of vitamin D in cancer prevention

Vitamin D, also known as cholecalciferol, is the precursor to the active steroid hormone 1, 25-dihydroxyvitamin D3 (calcitriol; 1, 25(OH)2D3). The main physiological role for 1, 25(OH)2D3 is to regulate calcium and inorganic phosphate homeostasis for bone health. More recently, vitamin D has been investigated for its effects in the prevention and treatment of a variety of diseases such as cancer, autoimmune disorders, and cardiovascular disease. Preclinical data strongly support a role for vitamin D in the prevention of cancer through its anti-proliferative, pro-apoptotic, and anti-angiogenic effects on cells. Epidemiologic and clinical studies have shown mixed data on the correlation between serum vitamin D levels and cancer risk. This report seeks to outline results from the most recent preclinical and clinical studies investigating the potential role of vitamin D in cancer prevention.

Gene Signatures of 1,25-Dihydroxyvitamin D3 Exposure in Normal and Transformed Mammary Cells

To elucidate potential mediators of vitamin D receptor (VDR) action in breast cancer, we profiled the genomic effects of its ligand 1,25-dihydroxyvitamin D3 (1,25D) in cells derived from normal mammary tissue and breast cancer. In non-transformed hTERT-HME cells, 483 1,25D responsive entities in 42 pathways were identified, whereas in MCF7 breast cancer cells, 249 1,25D responsive entities in 31 pathways were identified. Only 21 annotated genes were commonly altered by 1,25D in both MCF7 and hTERT-HME cells. Gene set enrichment analysis highlighted eight pathways (including senescence/autophagy, TGFβ signaling, endochondral ossification, and adipogenesis) commonly altered by 1,25D in hTERT-HME and MCF7 cells. Regulation of a subset of immune (CD14, IL1RL1, MALL, CAMP, SEMA6D, TREM1, CSF1, IL33, TLR4) and metabolic (ITGB3, SLC1A1, G6PD, GLUL, HIF1A, KDR, BIRC3) genes by 1,25D was confirmed in hTERT-HME cells and similar changes were observed in another comparable non-transformed mammary cell line (HME cells). The effects of 1,25D on these genes were retained in HME cells expressing SV40 large T antigen but were selectively abrogated in HME cells expressing SV40 + RAS and in MCF7 cells. Integration of the datasets from hTERT-HME and MCF7 cells with publically available RNA-SEQ data from 1,25D treated SKBR3 breast cancer cells enabled identification of an 11-gene signature representative of 1,25D exposure in all three breast-derived cell lines. Four of these 11 genes (CYP24A1, CLMN, EFTUD1, and SERPINB1) were also identified as 1,25D responsive in human breast tumor explants, suggesting that this gene signature may prove useful as a biomarker of vitamin D exposure in breast tissue.

1,25-Dihydroxyvitamin D induces the glutamate transporter SLC1A1 and alters glutamate handling in non-transformed mammary cells

Genomic profiling of immortalized human mammary epithelial (hTERT-HME1) cells identified several metabolic genes, including the membrane glutamate transporter, SLC1A1, as 1,25-dihydroxyvitamin D3 (1,25D) regulated. In these studies we have surveyed the effects of 1,25D on known glutamate transporters and evaluated its impact on cellular glutamate handling. We confirm that expression of SLC1A1 and all of its known transcript variants are significantly upregulated in hTERT-HME1 cells following 1,25D treatment. Expression of the full-length cognate protein, EAAT3, is correspondingly increased in 1,25D treated hTERT-HME1 cells. Under the same conditions, the expression of two other glutamate transporters--SLC1A6 (EAAT4) and SLC1A2 (EAAT2 or GLT-1)--is enhanced by 1,25D while that of SLC1A3 (EAAT1 or GLAST) and SLC7A11 (xCT) is decreased. Glutamate is not essential for growth of hTERT-HME1 cells, and supplemental glutamate (up to 0.5 mM) does not abrogate the growth inhibitory effects of 1,25D. These data suggest that extracellular glutamate is not a major contributor to cellular energy metabolism in hTERT-HME1 cells under basal conditions and that the growth inhibitory effects of 1,25D are not secondary to its effects on glutamate handling. Instead, the effects of 1,25D on glutamate transporters translated to a decrease in cellular glutamate concentration and an increase in media glutamate concentration, suggesting that one or more of these transporters functions to export glutamate in response to 1,25D exposure. The reduced cellular glutamate concentration may also reflect its incorporation into the cellular glutathione (GSH) pool, which is increased upon 1,25D treatment. In support of this concept, the expression of GCLC (which codes for the rate-limiting enzyme in GSH synthesis) and genes which generate reducing equivalents in the form of NADPH (ie, G6PD, PGD, IDH2) are elevated in 1,25D-treated cells. Taken together, these data identify 1,25D as a physiological regulator of multiple membrane glutamate transporters that impacts on overall cellular glutamate handling.

PTH and Vitamin D

PTH and Vitamin D are two major regulators of mineral metabolism. They play critical roles in the maintenance of calcium and phosphate homeostasis as well as the development and maintenance of bone health. PTH and Vitamin D form a tightly controlled feedback cycle, PTH being a major stimulator of vitamin D synthesis in the kidney while vitamin D exerts negative feedback on PTH secretion. The major function of PTH and major physiologic regulator is circulating ionized calcium. The effects of PTH on gut, kidney, and bone serve to maintain serum calcium within a tight range. PTH has a reciprocal effect on phosphate metabolism. In contrast, vitamin D has a stimulatory effect on both calcium and phosphate homeostasis, playing a key role in providing adequate mineral for normal bone formation. Both hormones act in concert with the more recently discovered FGF23 and klotho, hormones involved predominantly in phosphate metabolism, which also participate in this closely knit feedback circuit. Of great interest are recent studies demonstrating effects of both PTH and vitamin D on the cardiovascular system. Hyperparathyroidism and vitamin D deficiency have been implicated in a variety of cardiovascular disorders including hypertension, atherosclerosis, vascular calcification, and kidney failure. Both hormones have direct effects on the endothelium, heart, and other vascular structures. How these effects of PTH and vitamin D interface with the regulation of bone formation are the subject of intense investigation.

Penalized Ordinal Regression Methods for Predicting Stage of Cancer in High-Dimensional Covariate Spaces

The pathological description of the stage of a tumor is an important clinical designation and is considered, like many other forms of biomedical data, an ordinal outcome. Currently, statistical methods for predicting an ordinal outcome using clinical, demographic, and high-dimensional correlated features are lacking. In this paper, we propose a method that fits an ordinal response model to predict an ordinal outcome for high-dimensional covariate spaces. Our method penalizes some covariates (high-throughput genomic features) without penalizing others (such as demographic and/or clinical covariates). We demonstrate the application of our method to predict the stage of breast cancer. In our model, breast cancer subtype is a nonpenalized predictor, and CpG site methylation values from the Illumina Human Methylation 450K assay are penalized predictors. The method has been made available in the ordinalgmifs package in the R programming environment.

Enhancing FTS (Salirasib) efficiency via combinatorial treatment

The Ras oncogene transmits signals, which regulate various cellular processes including cell motility, differentiation, growth and death. Since Ras signalling is abnormally activated in more than 30% of human cancers, Ras and its downstream signalling pathways are considered good targets for therapeutic interference. Ras is post-translationally modified by the addition of a farnesyl group, which permits its attachment to the plasma membrane. Exploiting this knowledge, a synthetic Ras inhibitor, S-trans, trans-farnesylthiosalicylic acid (FTS; Salirasib), was developed. FTS resembles the farnesylcysteine group of Ras, and acts as an effective Ras antagonist. In the present review, the effect of FTS in combination with various other drugs, as tested in vitro and in vivo, and its therapeutic potential are discussed. As reviewed, FTS cooperates with diverse therapeutic agents, which significantly improves treatment outcome. Therefore, combinations of FTS with other agents have a potential to serve as anti-cancer or anti-inflammatory therapies.