Vitamin D deficiency promotes growth of MCF-7 human breast cancer in a rodent model of osteosclerotic bone metastasis

Low baseline vitamin D levels increase the risk of bone metastases among females with breast cancer - Hospital based cohort study

BACKGROUND

Serum vitamin D (Vit-D) has been linked to the development of breast cancer (BC); however, their effect on pathological features and outcomes is undetermined. The purpose of this study was to examine the prognostic significance of baseline Vit-D levels and their effect on clinical outcomes.

METHODS

We evaluated baseline serum Vit-D levels and baseline clinic-pathological features of female patients with non-metastatic BC between October 2018 and December 2019. A low Vit-D level was described as less than 30 nanogram per liter (ng/l). Patients were observed for a median of 24 months. To evaluate relationships between qualitative variables, the chi-square test was used. The Kaplan-Meier technique was used for survival analysis, and the log-rank test was used to compare the two survival curves. Correlation analysis was also used to examine the link between Vit-D levels and clinical outcomes.

RESULTS

The eligibility criteria were fulfilled by 221 patients. The median age of onset was (50.7). The median Vit-D level was (23.1 ng/l) with a range of (4-46 ng/l). Approximately half of the patients (56.5%) had Vit-D levels < 30 ng/l, with HER2 positive and triple negative (TNBC) patients having a greater proportion of low Vit-D levels (p = <0.001). Patients with low baseline Vit-D levels had a larger tumor size, more positive lymph nodes, and were diagnosed at a later stage. Following follow-up, Vit-D deficiency was associated with a significantly increased risk of bone metastases (HR 3.37, 95% CI 1.32-8.59, p = 0.006), and Vit-D levels were significantly correlated with disease-free survival (DFS) and overall survival (OS) (r = 0.850, r = 0.573, p < 0.00, p < 0.001, respectively).

CONCLUSIONS

Low serum Vit-D is associated with advanced stage and adverse characteristics. It is more prevalent in HER-2 positive and TNBC patients; it increases the chance of bone metastases, and has a significant correlation with DFS and OS.

Vitamin D Receptor Expression Is Significantly Decreased in Bone Metastases Compared to Matched Primary Breast Cancer Tumours

There is ample evidence today that vitamin D signalling via the vitamin D receptor (VDR) plays a pivotal role in cancer growth and metastasis. The aim of this study was to analyse VDR expression of primary breast cancer and corresponding bone metastases tissue samples. Collectively, 15 sample pairs and 11 samples of patients that did not develop metastases were analysed histologically for VDR expression (n = 41). Overall, VDR expression was significantly lower in bone metastases compared to primary tumour samples (p < .0001). Downregulation of the VDR in breast cancer cells may define a critical turning point in oncogenesis that accelerates cancer cell dissemination and metastases.

Prognostic role of plasma vitamin D and its association with disease characteristics in germ cell tumours

Background

Testicular cancer is the most common malignancy among young men. Vitamin D has pluripotent effects on cancer pathogenesis and plays a role in the metastatic cascade. The aim of this study is to analyze plasma vitamin D in association with clinico-pathological findings and prognosis in patients with germ-cell tumors (GCTs).

Methods

This study included 120 newly diagnosed and/or relapsed GCT patients treated from April 2013 to July 2020, for whom plasma was available in the biobank. Blood samples were drawn the 1st chemotherapy cycle as well as before the 2nd cycle. Plasma vitamin D was measured using ELISA and correlated with disease characteristics and the outcome. For survival analysis, the cohort was dichotomized into "low" and "high" based on median vitamin D.

Results

There was no significant difference in vitamin D plasma levels between healthy donors and GCT patients (p = 0.71). Vitamin D level was not associated with disease characteristics except for brain metastases, where patients with brain metastases had a vitamin D level that was 32% lower compared to patients without brain metastases, p = 0.03. Vitamin D was also associated with response to chemotherapy, with an approximately 32% lower value in patients with an unfavorable response compared to a favorable response, p = 0.02. Moreover, low plasma levels of vitamin D were significantly associated with disease recurrence and inferior progression-free survival (PFS), but not with overall survival (OS) (HR = 3.02, 95% CI 1.36-6.71, p = 0.01 for PFS and HR = 2.06, 95% CI 0.84-5.06, p = 0.14 for OS, respectively).

Conclusion

Our study suggests the prognostic value of pretreatment vitamin D concentrations in GCT patients. Low plasma vitamin D was associated with an unfavorable response to therapy and disease recurrence. However, it remains to be determined whether the biology of the disease confirms a causative role for low vitamin D and whether its supplementation affects the outcome.

Bone Metastases of Diverse Primary Origin Frequently Express the VDR (Vitamin D Receptor) and CYP24A1

Active vitamin D (1,25(OH)2D3) is known to exert direct anti-cancer actions on various malignant tissues through binding to the vitamin D receptor (VDR). These effects have been demonstrated in breast, prostate, renal and thyroid cancers, which all have a high propensity to metastasise to bone. In addition, there is evidence that vitamin D catabolism via 24-hydroxylase (CYP24A1) is altered in tumour cells, thus, reducing local active vitamin D levels in cancer cells. The aim of this study was to assess VDR and CYP24A1 expression in various types of bone metastases by using immunohistochemistry. Overall, a high total VDR protein expression was detected in 59% of cases (39/66). There was a non-significant trend of high-grade tumours towards the low nuclear VDR expression (p = 0.07). Notably, patients with further distant metastases had a reduced nuclear VDR expression (p = 0.03). Furthermore, a high CYP24A1 expression was detected in 59% (39/66) of bone metastases. There was a significant positive correlation between nuclear VDR and CYP24A1 expression (p = 0.001). Collectively, the VDR and CYP24A1 were widely expressed in a multitude of bone metastases, pointing to a potential role of vitamin D signalling in cancer progression. This is of high clinical relevance, as vitamin D deficiency is frequent in patients with bone metastases.

Systemic effects of abnormal bone resorption on muscle, metabolism, and cognition

Skeletal tissue is dynamic, undergoing constant remodeling to maintain musculoskeletal integrity and balance in the human body. Recent evidence shows that apart from maintaining homeostasis in the local microenvironment, the skeleton systemically affects other tissues. Several cancer-associated and noncancer-associated bone disorders can disrupt the physiological homeostasis locally in the bone microenvironment and indirectly contribute to dysregulation of systemic body function. The systemic effects of bone on the regulation of distant organ function have not been widely explored. Recent evidence suggests that bone can interact with skeletal muscle, pancreas, and brain by releasing factors from mineralized bone matrix. Currently available bone-targeting therapies such as bisphosphonates and denosumab inhibit bone resorption, decrease morbidity associated with bone destruction, and improve survival. Bisphosphonates have been a standard treatment for bone metastases, osteoporosis, and cancer treatment-induced bone diseases. The extraskeletal effects of bisphosphonates on inhibition of tumor growth are known. However, our knowledge of the effects of bisphosphonates on muscle weakness, hyperglycemia, and cognitive defects is currently evolving. To be able to identify the molecular link between bone and distant organs during abnormal bone resorption and then treat these abnormalities and prevent their systemic effects could improve survival benefits. The current review highlights the link between bone resorption and its systemic effects on muscle, pancreas, and brain.

Influences of the 3D microenvironment on cancer cell behaviour and treatment responsiveness: A recent update on lung, breast and prostate cancer models

The majority of in vitro studies assessing cancer treatments are performed in two-dimensional (2D) monolayers and are subsequently validated in in vivo animal models. However, 2D models fail to accurately model the tumour microenvironment. Furthermore, animal models are not directly applicable to mimic the human scenario. Three-dimensional (3D) culture models may help to address the discrepancies of 2D and animal models. When cancer cells escape the primary tumour, they can invade at distant organs building secondary tumours, called metastasis. The development of metastasis leads to a dramatic decrease in the life expectancy of patients. Therefore, 3D systems to model the microenvironment of metastasis have also been developed. Several studies have demonstrated changes in cell behaviour and gene expression when cells are cultured in 3D compared to 2D and concluded a better comparability to cells in vivo. Of special importance is the effect seen in response to anti-cancer treatments as models are built primarily to serve as drug-testing platforms. This review highlights these changes between cancer cells grown in 2D and 3D models for some of the most common cancers including lung, breast and prostate tumours. In addition to models aiming to mimic the primary tumour site, the effects of 3D cell culturing in bone metastasis models are also described. STATEMENT OF SIGNIFICANCE: Most in vitro studies in cancer research are performed in 2D and are subsequently validated in in vivo animal models. However, both models possess numerous limitations: 2D models fail to accurately model the tumour microenvironment while animal models are expensive, time-consuming and can differ considerably from humans. It is accepted that the cancer microenvironment plays a critical role in the disease, thus, 3D models have been proposed as a potential solution to address the discrepancies of 2D and animal models. This review highlights changes in cell behaviour, including proliferation, gene expression and chemosensitivity, between cancer cells grown in 2D and 3D models for some of the most common cancers including lung, breast and prostate cancer as well as bone metastasis.

Animal Models of Metastatic Lesions to the Spine: a Focus on Epidural Spinal Cord Compression

Epidural spinal cord compression (ESCC) secondary to spine metastases is one of the most devastating sequelae of primary cancer as it may lead to muscle weakness, paresthesia, pain, and paralysis. Spine metastases occur through a multi-step process that can result in eventual ESCC; however, the lack of a preclinical model to effectively recapitulate each step of this metastatic cascade and the symptom burden of ESCC has limited our understanding of this disease process. In this review, we discuss animal models that best recapitulate ESCC; we start with a broad discussion of commonly used models of bone metastasis and end with a focused discussion of models used to specifically study ESCC. Orthotopic models offer the most authentic recapitulation of metastasis development; however, they rarely result in symptomatic ESCC and are challenging to replicate. Conversely, models that involve injection of tumor cells directly into the bloodstream or bone better mimic the symptoms of ESCC; however, they provide limited insight into the epithelial to mesenchymal transition (EMT) and natural hematogenous spread of tumor cell. Therefore, until an ideal model is created, it is critical to select an animal model that is specifically designed to answer the scientific question of interest.

Vitamin D Regulates CXCL12/CXCR4 and Epithelial-to-Mesenchymal Transition in a Model of Breast Cancer Metastasis to Lung

Vitamin D deficiency is associated with poor cancer outcome in humans, and administration of vitamin D or its analogs decreases tumor progression and metastasis in animal models. Using the mouse mammary tumor virus-polyoma middle T antigen (MMTV-PyMT) model of mammary cancer, we previously demonstrated a significant acceleration of carcinogenesis in animals on a low vitamin D diet and a reduction in spontaneous lung metastases when mice received vitamin D through perfusion. We investigate here the action mechanism for vitamin D in lung metastasis in the same non-immunodeficient model and demonstrate that it involves the control of epithelial to mesenchymal transition as well as interactions between chemokine C-X-C motif chemokine 12 (CXCL12) and its receptor C-X-C chemokine receptor type 4 (CXCR4). In vitro, 10-9M vitamin D treatment modifies the phenotype of MMTV-PyMT primary mammary tumor cells and significantly decreases their invasiveness and mammosphere formation capacity by 40% and 50%, respectively. Vitamin D treatment also inhibits phospho-signal transducer and activator of transcription 3 (p-STAT3), zinc finger E-box-binding homeobox 1 (Zeb1), and vimentin by 52%, 75%, and 77%, respectively, and increases E-cadherin by 87%. In vivo, dietary vitamin D deficiency maintains high levels of Zeb1 and p-STAT3 in cells from primary mammary tumors and increases CXCL12 expression in lung stroma by 64%. In lung metastases, vitamin D deficiency increases CXCL12/CXCR4 co-localization by a factor of 2.5. These findings indicate an involvement of vitamin D in mammary cancer "seed" (primary tumor cell) and "soil" (metastatic site) and link vitamin D deficiency to epithelial-to-mesenchymal transition (EMT), CXCL12/CXCR4 signaling, and accelerated metastasis, suggesting vitamin D repleteness in breast cancer patients could enhance the efficacy of co-administered therapies in preventing spread to distant organs.

RANKL immunisation inhibits prostate cancer metastasis by modulating EMT through a RANKL-dependent pathway

Prostate cancer (PCa) morbidity in the majority of patients is due to metastatic events, which are a clinical obstacle. Therefore, a better understanding of the mechanism underlying metastasis is imperative if we are to develop novel therapeutic strategies. Receptor activator of nuclear factor kappa-B (NF-κB) ligand (RANKL) regulates bone remodelling. Thus, agents that suppress RANKL signalling may be useful pharmacological treatments. Here, we used preclinical experimental models to investigate whether an inactive form of RANKL affects bone metastasis in RANKL-induced PCa. RANKL was associated with epithelial–mesenchymal transition (EMT) and expression of metastasis-related genes in PC3 cells. Therefore, we proposed a strategy to induce anti-cytokine antibodies using mutant RANKL as an immunogen. RANKL promoted migration and invasion of PC3 cells through EMT, and induced a significant increase in binding of β-catenin to TCF-4, an EMT-induced transcription factor in PCa cells, via mitogen-activated protein kinase and β-catenin/TCF-4 signalling. Thus, RANKL increased EMT and the metastatic properties of PC3 cells, suggesting a role as a therapeutic target to prevent PCa metastasis. Treatment with mutant RANKL reduced EMT and metastasis of PC3 PCa cells in an experimental metastasis model. Thus, mutant RANKL could serve as a potential vaccine to prevent and treat metastatic PCa.

The role of vitamin D and vitamin D deficiency in orthopaedics and traumatology-a narrative overview of the literature

Vitamin D is considered to play an important role in musculoskeletal health. It’s classical function is the regulation of calcium and phosphate homeostasis, thus ensuring a balanced bone metabolism that is characterised by an equal amount of bone resorption and bone formation. In the past decades, a plethora of pre-clinical and clinical studies reporting on potential health-beneficial properties of vitamin D have emerged. Moreover, there is an abundance of reports highlighting vitamin D deficiency and insufficiency in patients with almost innumerable diseases. Further, it is estimated that more than one billion people globally are affected by insufficient vitamin D levels. As such, research on vitamin D has been particularly popular over the past years. In orthopaedics and traumatology, most studies describe favourable effects of vitamin D in general. However, the relative importance of vitamin D is oftentimes debated. In this narrative review of the literature, we consider first, the properties of vitamin D and how vitamin D, vitamin D deficiency and the vitamin D receptor (VDR) impact on musculoskeletal health. Secondly, we provide an overview of studies reporting the prevalence of vitamin D deficiency in traumatology and diverse orthopaedic diseases including bone oncology. Lastly, we emphasise recent findings and touch on future perspectives in vitamin D research.

Micronutrients and Breast Cancer Progression: A Systematic Review

Epidemiological studies on micronutrient consumption have reported protective associations in the incidence and/or progression of various cancer types. Supplementation with some of these micronutrients has been analyzed, showing chemoprotection, low toxicity, antiproliferation, and the ability to modify epigenetic signatures in various cancer models. This review investigates the reported effects of micronutrient intake or supplementation in breast cancer progression. A PubMed search was conducted with the keywords "micronutrients breast cancer progression", and the results were analyzed. The selected micronutrients were vitamins (C, D, and E), folic acid, metals (Cu, Fe, Se, and Zn), fatty acids, polyphenols, and iodine. The majority of in vitro models showed antiproliferative, cell-cycle arrest, and antimetastatic effects for almost all the micronutrients analyzed, but these effects do not reflect animal or human studies. Only one clinical trial with vitamin D and one pilot study with molecular iodine showed favorable overall survival and disease-free interval.

Prediagnostic 25-Hydroxyvitamin D Concentrations in Relation to Tumor Molecular Alterations and Risk of Breast Cancer Recurrence

BACKGROUND

Although vitamin D inhibits breast tumor growth in experimental settings, the findings from population-based studies remain inconclusive. Our goals were to investigate the association between prediagnostic plasma 25-hydroxyvitamin D [25(OH)D] concentration and breast cancer recurrence in prospective epidemiologic studies and to explore the molecular underpinnings linking 25(OH)D to slower progression of breast cancer in the Nurses' Health Studies (NHS, N = 659).

METHODS

Plasma 25(OH)D was measured with a high-affinity protein-binding assay and a radioimmunoassay. We profiled transcriptome-wide gene expression in breast tumors using microarrays. Hazard ratios (HR) of breast cancer recurrence were estimated from covariate-adjusted Cox regressions. We examined differential gene expression in association with 25(OH)D and employed pathway analysis. We derived a gene expression score for 25(OH)D, and assessed associations between the score and cancer recurrence.

RESULTS

Although 25(OH)D was not associated with breast cancer recurrence overall [HR = 0.97; 95% confidence interval (CI), 0.88-1.08], the association varied by estrogen-receptor (ER) status (P _interaction = 0.005). Importantly, among ER-positive stage I to III cancers, every 5 ng/mL increase in 25(OH)D was associated with a 13% lower risk of recurrence (HR = 0.87; 95% CI, 0.76-0.99). A null association was observed for ER-negative cancers (HR = 1.07; 95% CI, 0.91-1.27). Pathway analysis identified multiple gene sets that were significantly (FDR < 5%) downregulated in ER-positive tumors of women with high 25(OH)D (≥30 ng/mL), compared with those with low levels (<30 ng/mL). These gene sets are primarily involved in tumor proliferation, migration, and inflammation. 25(OH)D score derived from these gene sets was marginally associated with reduced risk of recurrence in ER-positive diseases (HR = 0.77; 95% CI, 0.59-1.01) in the NHS studies; however no association was noted in METABRIC, suggesting that further refinement is need to improve the generalizability of the score.

CONCLUSIONS

Our findings support an intriguing line of research for studies to better understand the mechanisms underlying the role of vitamin D in breast tumor progression, particularly for the ER-positive subtype.

IMPACT

Vitamin D may present a personal-level secondary-prevention strategy for ER-positive breast cancer.

Loss of the Vitamin D Receptor in Human Breast Cancer Cells Promotes Epithelial to Mesenchymal Cell Transition and Skeletal Colonization

Expression of the vitamin D receptor (VDR) is thought to be associated with neoplastic progression. However, the role of the VDR in breast cancer metastasis to bone and the molecular mechanisms underlying this process are unknown. Employing a rodent model (female Balb/c nu/nu mice) of systemic metastasis, we here demonstrate that knockdown of the VDR strongly increases the metastatic potential of MDA-MB-231 human breast cancer cells to bone, resulting in significantly greater skeletal tumor burden. Ablation of VDR expression promotes cancer cell mobility (migration) and invasiveness, thereby facilitating skeletal colonization. Mechanistically, these changes in tumor cell behavior are attributable to shifts in the expression of proteins involved in cell adhesion, proliferation, and cytoskeletal organization, patterns characteristic for epithelial-to-mesenchymal cell transition (EMT). In keeping with these experimental findings, analyses of human breast cancer specimens corroborated the association between VDR expression, EMT-typical changes in protein expression patterns, and clinical prognosis. Loss of the VDR in human breast cancer cells marks a critical point in oncogenesis by inducing EMT, promoting the dissemination of cancer cells, and facilitating the formation of tumor colonies in bone. © 2019 American Society for Bone and Mineral Research.

Emerging and Established Models of Bone Metastasis

Metastasis is the leading cause of cancer-related death and drives patient morbidity as well as healthcare costs. Bone is the primary site of metastasis for several cancers—breast and prostate cancers in particular. Efforts to treat bone metastases have been stymied by a lack of models to study the progression, cellular players, and signaling pathways driving bone metastasis. In this review, we examine newly described and classic models of bone metastasis. Through the use of current in vivo, microfluidic, and in silico computational bone metastasis models we may eventually understand how cells escape the primary tumor and how these circulating tumor cells then home to and colonize the bone marrow. Further, future models may uncover how cells enter and then escape dormancy to develop into overt metastases. Recreating the metastatic process will lead to the discovery of therapeutic targets for disrupting and treating bone metastasis.

The vitamin D receptor is involved in the regulation of human breast cancer cell growth via a ligand-independent function in cytoplasm

Vitamin D has pleiotropic effects on multiple tissues, including malignant tumors. Vitamin D inhibits breast cancer growth through activation of the vitamin D receptor (VDR) and via classical nuclear signaling pathways. Here, we demonstrate that the VDR can also function in the absence of its ligand to control behaviour of human breast cancer cells both outside and within the bone microenvironment. Stable shRNA expression was used to knock down VDR expression in MCF-7 cells, generating two VDR knockdown clonal lines. In ligand-free culture, knockdown of VDR in MCF-7 cells significantly reduced proliferation and increased apoptosis, suggesting that the VDR plays a ligand-independent role in cancer cell growth. Implantation of these VDR knockdown cells into the mammary fat pad of nude mice resulted in reduced tumor growth in vivo compared with controls. In the intra-tibial xenograft model, VDR knockdown greatly reduced the ability of the cells to form tumors in the bone microenvironment. The in vitro growth of VDR knockdown cells was rescued by the expression of a mutant form of VDR which is unable to translocate to the nucleus and hence accumulates in the cytoplasm. Thus, our data indicate that in the absence of ligand, the VDR promotes breast cancer growth both in vitro and in vivo and that cytoplasmic accumulation of VDR is sufficient to produce this effect in vitro. This new mechanism of VDR action in breast cancer cells contrasts the known anti-proliferative nuclear actions of the VDR-vitamin D ligand complex.

Polyurethane foam scaffold as in vitro model for breast cancer bone metastasis

Breast cancer (BC) represents the most incident cancer case in women (29%), with high mortality rate. Bone metastasis occurs in 20-50% cases and, despite advances in BC research, the interactions between tumor cells and the metastatic microenvironment are still poorly understood. In vitro 3D models gained great interest in cancer research, thanks to the reproducibility, the 3D spatial cues and associated low costs, compared to in vivo and 2D in vitro models. In this study, we investigated the suitability of a poly-ether-urethane (PU) foam as 3D in vitro model to study the interactions between BC tumor-initiating cells and the bone microenvironment. PU foam open porosity (>70%) appeared suitable to mimic trabecular bone structure. The PU foam showed good mechanical properties under cyclic compression (E=69-109kPa), even if lower than human trabecular bone. The scaffold supported osteoblast SAOS-2 cell line proliferation, with no cytotoxic effects. Human adipose derived stem cells (ADSC) were cultured and differentiated into osteoblast lineage on the PU foam, as shown by alizarin red staining and RT-PCR, thus offering a bone biomimetic microenvironment to the further co-culture with BC derived tumor-initiating cells (MCFS). Tumor aggregates were observed after three weeks of co-culture by e-cadherin staining and SEM; modification in CaP distribution was identified by SEM-EDX and associated to the presence of tumor cells. In conclusion, we demonstrated the suitability of the PU foam to reproduce a bone biomimetic microenvironment, useful for the co-culture of human osteoblasts/BC tumor-initiating cells and to investigate their interaction.

STATEMENT OF SIGNIFICANCE

3D in vitro models represent an outstanding alternative in the study of tumor metastases development, compared to traditional 2D in vitro cultures, which oversimplify the 3D tissue microenvironment, and in vivo studies, affected by low reproducibility and ethical issues. Several scaffold-based 3D in vitro models have been proposed to recapitulate the development of metastases in different body sites but, still, the crucial challenge is to correctly mimic the tissue to be modelled in terms of physical, mechanical and biological properties. Here, we prove the suitability of a porous polyurethane foam, synthesized using an appropriate formulaton, in mimicking the bone tissue microenvironment and in reproducing the metastatic colonization derived from human breast cancer, particularly evidencing the devastating effects on the bone extracellular matrix caused by metastatic spreading.

Chronic moderate ethanol intake differentially regulates vitamin D hydroxylases gene expression in kidneys and xenografted breast cancer cells in female mice

Factors affecting vitamin D metabolism may preclude anti-carcinogenic effects of its active metabolite calcitriol. Chronic ethanol consumption is an etiological factor for breast cancer that affects vitamin D metabolism; however, the mechanisms underlying this causal association have not been fully clarified. Using a murine model, we examined the effects of chronic moderate ethanol intake on tumoral and renal CYP27B1 and CYP24A1 gene expression, the enzymes involved in calcitriol synthesis and inactivation, respectively. Ethanol (5% w/v) was administered to 25-hydroxyvitamin D₃-treated or control mice during one month. Afterwards, human breast cancer cells were xenografted and treatments continued another month. Ethanol intake decreased renal Cyp27b1 while increased tumoral CYP24A1 gene expression.Treatment with 25-hydroxyvitamin D₃ significantly stimulated CYP27B1 in tumors of non-alcohol-drinking mice, while increased both renal and tumoral CYP24A1. Coadministration of ethanol and 25-hydroxyvitamin D₃ reduced in 60% renal 25-hydroxyvitamin D₃-dependent Cyp24a1 upregulation (P<0.05). We found 5 folds higher basal Cyp27b1 than Cyp24a1 gene expression in kidneys, whereas this relation was inverted in tumors, showing 5 folds more CYP24A1 than CYP27B1. Tumor expression of the calcitriol target cathelicidin increased only in 25-hydroxyvitamin D₃-treated non-ethanol drinking animals (P<0.05). Mean final body weight was higher in 25-hydroxyvitamin D₃ treated groups (P<0.001). Overall, these results suggest that moderate ethanol intake decreases renal and tumoral 25-hydroxyvitamin D₃ bioconversion into calcitriol, while favors degradation of both vitamin D metabolites in breast cancer cells. The latter may partially explain why alcohol consumption is associated with vitamin D deficiency and increased breast cancer risk and progression.

1,25(OH)2D3 deficiency increases TM40D tumor growth in bone and accelerates tumor-induced bone destruction in a breast cancer bone metastasis model

Breast cancer is one of the most common malignancies and bone is the commonest site of distant metastases. Evidences indicate that adequate supply of vitamin D will decrease the morbidity and mortality of breast cancer. However, the main role of vitamin D deficiency in breast cancer bone metastases remains unclear. In this study, the relationship between vitamin D and breast cancer bone metastases were evaluated. Results showed that 1,25(OH)₂D₃ can not only inhibit the proliferation, migration and invasion of breast cancer cell TM40D in vitro, but also attenuate the breast cancer cell TM40D-induced bone destruction in vivo, whose underlying mechanism was at least partially through decreasing the number of the osteoclasts. To our knowledge, this is the first to use 1-alpha-hydroxylase [1α(OH)ase] knockout mice which characterized vitamin D deficiency to establish the breast cancer bone metastases model. Based on this model, we also found that vitamin D deficiency will accelerate the osteolytic lesions, and 1,25(OH)₂D₃ supplement will restrain osteolytic lesions. Therefore, these findings suggest that vitamin D has the potential capacity to be a therapeutic agent for the breast cancer bone metastases.

Loss of the vitamin D receptor in human breast and prostate cancers strongly induces cell apoptosis through downregulation of Wnt/β-catenin signaling

Vitamin D co-regulates cell proliferation, differentiation and apoptosis in numerous tissues, including cancers. The known anti-proliferative and pro-apoptotic actions of the active metabolite of vitamin D, 1,25-dihydroxy-vitamin D [1,25(OH)₂D] are mediated through binding to the vitamin D receptor (VDR). Here, we report on the unexpected finding that stable knockdown of VDR expression in the human breast and prostate cancer cell lines, MDA-MB-231 and PC3, strongly induces cell apoptosis and inhibits cell proliferation in vitro. Implantation of these VDR knockdown cells into the mammary fat pad (MDA-MB-231), subcutaneously (PC3) or intra-tibially (both cell lines) in immune-incompetent nude mice resulted in reduced tumor growth associated with increased apoptosis and reduced cell proliferation compared with controls. These growth-retarding effects of VDR knockdown occur in the presence and absence of vitamin D and are independent of whether cells were grown in bone or soft tissues. Transcriptome analysis of VDR knockdown and non-target control cell lines demonstrated that loss of the VDR was associated with significant attenuation in the Wnt/β-catenin signaling pathway. In particular, cytoplasmic and nuclear β-catenin protein levels were reduced with a corresponding downregulation of downstream genes such as Axin2, Cyclin D1, interleukin-6 (IL-6), and IL-8. Stabilization of β-catenin using the GSK-3β inhibitor BIO partly reversed the growth-retarding effects of VDR knockdown. Our results indicate that the unliganded VDR possesses hitherto unknown functions to promote breast and prostate cancer growth, which appear to be operational not only within but also outside the bone environment. These novel functions contrast with the known anti-proliferative nuclear actions of the liganded VDR and may represent targets for new diagnostic and therapeutic approaches in breast and prostate cancer.

1,25D3 differentially suppresses bladder cancer cell migration and invasion through the induction of miR-101-3p

Metastasis is the major cause of bladder cancer death. 1,25D3, the active metabolite of vitamin D, has shown anti-metastasis activity in several cancer model systems. However, the role of 1,25D3 in migration and invasion in bladder cancer is unknown. To investigate whether 1,25D3 affects migration and invasion, four human bladder cell lines with different reported invasiveness were selected: low-invasive T24 and 253J cells and highly invasive 253J-BV and TCCSUP cells. All of the four bladder cancer cells express endogenous and inducible vitamin D receptor (VDR) as examined by immunoblot analysis. 1,25D3 had no effect on the proliferation of bladder cancer cells as assessed by MTT assay. In contrast, 1,25D3 suppressed migration and invasion in the more invasive 253J-BV and TCCSUP cells, but not in the low-invasive 253J and T24 cells using "wound" healing, chemotactic migration and Matrigel-based invasion assays. 1,25D3 promoted the expression of miR-101-3p and miR-126-3p in 253J-BV cells as examined by qRT-PCR. miR-101-3p inhibitor partially abrogated and pre-miR-101-3p further suppressed the inhibition of 1,25D3 on migration and invasion in 253J-BV cells. Further, 1,25D3 enhanced VDR recruitment to the promoter region of miR-101-3p using ChIP-qPCR assay. 1,25D3 enhanced the promoter activity of miR-101-3p as evaluated by luciferase reporter assay. Taken together, 1,25D3 suppresses bladder cancer cell migration and invasion in two invasive/migration competent lines but not in two less invasive/motile lines, which is partially through the induction of miR-101-3p expression at the transcriptional level.

Altered bone microarchitecture and gene expression profile due to calcium deficiency in a mouse model of myeloma

It is not clear why patients with an indolent form of multiple myeloma (MM) develop into an aggressive form with poor prognostic. We investigated the effect of a dietary calcium deficiency on tumor growth, osteolysis and gene expression in the 5T2MM murine model. Two groups of C57BL/KaLwRij mice received 5T2MM cells and started a diet with normal (0.8%; "normal-Ca-MM") or low calcium content (0.05%; "low-Ca-MM"). Two control groups (without 5T2MM cells) received either a normal or low calcium diet (normal-Ca and low-Ca groups). Tumor growth, osteolysis and marrow gene expression of the Wnt pathway, RANKL and MIP-1α were monitored at 6, 8 and 10 weeks (w) after cell injection. In low-Ca mice, serum level of PTH was higher after 10w; microCT showed trabecular bone loss and decrease of cortical thickness at the tibia. A higher M-protein level was evidenced at 10w and 4 mice developed paraplegia at 8/9w in low-Ca-MM group only. Numerous cortical perforations of the tibia were observed in MM groups with a marked decrease in cortical thickness in low-Ca-MM. At 6w, osteoclast number from the endosteum was significantly higher in low-Ca-MM compared to normal-Ca MM. This observation was not found at 8 and 10w. MicroCT of the lumbar vertebrae showed dramatic bone destruction in the low-Ca-MM group. qPCR revealed no difference in RANKL expression whereas differences were obtained in the expression of Lrp5/Lrp6 and MIP-1α from 6w. A low calcium diet induced higher bone destruction in the tibia and vertebra associated with an earlier decrease in bone formation level and a higher increase in bone resorption level at early time in the MM development.

Bone metastasis: the importance of the neighbourhood

During the past decade preclinical studies have defined many of the mechanisms used by tumours to hijack the skeleton and promote bone metastasis. This has led to the development and widespread clinical use of bone-targeted drugs to prevent skeletal-related events. This understanding has also identified a critical dependency between colonizing tumour cells and the cells of bone. This is particularly important when tumour cells first arrive in bone, adapt to their new microenvironment and enter a long-lived dormant state. In this Review, we discuss the role of different bone cell types in supporting disseminated tumour cell dormancy and reactivation, and highlight the new opportunities this provides for targeting the bone microenvironment to control dormancy and bone metastasis.

In vitro degradability, bioactivity and primary cell responses to bone cements containing mesoporous magnesium-calcium silicate and calcium sulfate for bone regeneration

Mesoporous calcium sulfate-based bone cements (m-CSBC) were prepared by introducing mesoporous magnesium-calcium silicate (m-MCS) with specific surface area (410.9 m² g(-1)) and pore volume (0.8 cm³ g(-1)) into calcium sulfate hemihydrate (CSH). The setting time of the m-CSBC was longer with the increase of m-MCS content while compressive strength decreased. The degradation ratio of m-CSBC increased from 48.6 w% to 63.5 w% with an increase of m-MCS content after soaking in Tris-HCl solution for 84 days. Moreover, the m-CSBC containing m-MCS showed the ability to neutralize the acidic degradation products of calcium sulfate and prevent the pH from dropping. The apatite could be induced on m-CSBC surfaces after soaking in SBF for 7 days, indicating good bioactivity. The effects of the m-CSBC on vitamin D3 sustained release behaviours were investigated. It was found that the cumulative release ratio of vitamin D3 from the m-CSBC significantly increased with the increase of m-MCS content after soaking in PBS (pH = 7.4) for 25 days. The m-CSBC markedly improved the cell-positive responses, including the attachment, proliferation and differentiation of MC3T3-E1 cells, suggesting good cytocompatibility. Briefly, m-CSBC with good bioactivity, degradability and cytocompatibility might be an excellent biocement for bone regeneration.

The Breast Cancer to Bone (B2B) Metastases Research Program: a multi-disciplinary investigation of bone metastases from breast cancer

Background

Bone is the most common site of breast cancer distant metastasis, affecting 50–70 % of patients who develop metastatic disease. Despite decades of informative research, the effective prevention, prediction and treatment of these lesions remains elusive. The Breast Cancer to Bone (B2B) Metastases Research Program consists of a prospective cohort of incident breast cancer patients and four sub-projects that are investigating priority areas in breast cancer bone metastases. These include the impact of lifestyle factors and inflammation on risk of bone metastases, the gene expression features of the primary tumour, the potential role for metabolomics in early detection of bone metastatic disease and the signalling pathways that drive the metastatic lesions in the bone.

Methods/Design

The B2B Research Program is enrolling a prospective cohort of 600 newly diagnosed, incident, stage I-IIIc breast cancer survivors in Alberta, Canada over a five year period. At baseline, pre-treatment/surgery blood samples are collected and detailed epidemiologic data is collected by in-person interview and self-administered questionnaires. Additional self-administered questionnaires and blood samples are completed at specified follow-up intervals (24, 48 and 72 months). Vital status is obtained prior to each follow-up through record linkages with the Alberta Cancer Registry. Recurrences are identified through medical chart abstractions. Each of the four projects applies specific methods and analyses to assess the impact of serum vitamin D and cytokine concentrations, tumour transcript and protein expression, serum metabolomic profiles and in vitro cell signalling on breast cancer bone metastases.

Discussion

The B2B Research Program will address key issues in breast cancer bone metastases including the association between lifestyle factors (particularly a comprehensive assessment of vitamin D status) inflammation and bone metastases, the significance or primary tumour gene expression in tissue tropism, the potential of metabolomic profiles for risk assessment and early detection and the signalling pathways controlling the metastatic tumour microenvironment. There is substantial synergy between the four projects and it is hoped that this integrated program of research will advance our understanding of key aspects of bone metastases from breast cancer to improve the prevention, prediction, detection, and treatment of these lesions.

Animal Models of Bone Metastasis

Bone is one of the most common sites of cancer metastasis in humans and is a significant source of morbidity and mortality. Bone metastases are considered incurable and result in pain, pathologic fracture, and decreased quality of life. Animal models of skeletal metastases are essential to improve the understanding of the molecular pathways of cancer metastasis and growth in bone and to develop new therapies to inhibit and prevent bone metastases. The ideal animal model should be clinically relevant, reproducible, and representative of human disease. Currently, an ideal model does not exist; however, understanding the strengths and weaknesses of the available models will lead to proper study design and successful cancer research. This review provides an overview of the current in vivo animal models used in the study of skeletal metastases or local tumor invasion into bone and focuses on mammary and prostate cancer, lymphoma, multiple myeloma, head and neck squamous cell carcinoma, and miscellaneous tumors that metastasize to bone.

Inhibition of MDA-MB-231 breast cancer cell migration and invasion activity by andrographolide via suppression of nuclear factor-κB-dependent matrix metalloproteinase-9 expression

Breast cancer is one of the most common types of cancer worldwide. The majority of patients with cancer succumb to the disease as a result of distant metastases (for example, in the bones), which cause severe complications. Despite advancements in breast cancer treatment, chemotherapeutic outcomes remain far from satisfactory, prompting a search for effective natural agents with few side‑effects. Andrographolide (AP), a natural diterpenoid lactone isolated from Andrographis paniculata, inhibits cancer cell growth. The current study aimed to examine the effect of AP on breast cancer cell proliferation, survival and progression in vitro and also its inhibitory activity on breast cancer bone metastasis in vivo. To achieve this, CCK8, flow cytometry, migration, invasion, western blot, PCR and luciferase reporter assay analyses were performed in vitro as well as establishing intratibial xenograft model of breast cancer bone metastasis in vivo. The results demonstrated that AP inhibits the migration and invasion of the MBA‑MD‑231 aggressive breast cancer cell line at non‑lethal concentrations, in addition to suppressing proliferation and inducing apoptosis at high concentrations in vitro. In vivo, AP significantly inhibited the growth of tumors planted in bone and attenuated cancer‑induced osteolysis. Tartrate‑resistant acid phosphatase staining revealed osteoclast activation in tumor‑bearing mice and AP was observed to attenuate this activation. The anti‑tumor activity of AP in vitro and in vivo correlates with the downregulation of the nuclear factor κB signaling pathway and the inhibition of matrix metalloproteinase‑9 expression levels. These results indicate that AP may be an effective anti‑tumor agent for the treatment of breast cancer bone metastasis.

A tissue-engineered humanized xenograft model of human breast cancer metastasis to bone

The skeleton is a preferred homing site for breast cancer metastasis. To date, treatment options for patients with bone metastases are mostly palliative and the disease is still incurable. Indeed, key mechanisms involved in breast cancer osteotropism are still only partially understood due to the lack of suitable animal models to mimic metastasis of human tumor cells to a human bone microenvironment. In the presented study, we investigate the use of a human tissue-engineered bone construct to develop a humanized xenograft model of breast cancer-induced bone metastasis in a murine host. Primary human osteoblastic cell-seeded melt electrospun scaffolds in combination with recombinant human bone morphogenetic protein 7 were implanted subcutaneously in non-obese diabetic/severe combined immunodeficient mice. The tissue-engineered constructs led to the formation of a morphologically intact ‘organ’ bone incorporating a high amount of mineralized tissue, live osteocytes and bone marrow spaces. The newly formed bone was largely humanized, as indicated by the incorporation of human bone cells and human-derived matrix proteins. After intracardiac injection, the dissemination of luciferase-expressing human breast cancer cell lines to the humanized bone ossicles was detected by bioluminescent imaging. Histological analysis revealed the presence of metastases with clear osteolysis in the newly formed bone. Thus, human tissue-engineered bone constructs can be applied efficiently as a target tissue for human breast cancer cells injected into the blood circulation and replicate the osteolytic phenotype associated with breast cancer-induced bone lesions. In conclusion, we have developed an appropriate model for investigation of species-specific mechanisms of human breast cancer-related bone metastasis in vivo.

Chemoprevention activity of 25-hydroxyvitamin D in the MMTV-PyMT mouse model of breast cancer

Development of oncologic conditions is often accompanied by inadequate vitamin D status. The chemoprevention ability of this molecule is of high interest for breast cancer, the most common malignancy in women worldwide. Because current effective vitamin D analogues, including the naturally occurring active metabolite 1,25-dihydroxycholecalciferol (1,25(OH)2D), frequently cause hypercalcemia at pharmacologic doses, the development of safer molecules for clinical chemopreventive use is essential. This study examines whether exogenously supplied prohormone 25-hydroxycholecalciferol (25(OH)D) can delay tumor progression in vivo without hypercalcemic effects. A low vitamin D diet (25 IU/kg) in the non-immunodeficient MMTV-PyMT mouse model of metastatic breast cancer revealed a significant acceleration of mammary neoplasia compared with normal diet (1,000 IU/kg). Systemic perfusion of MMTV-PyMT mice with 25(OH)D or 1,25(OH)2D delayed tumor appearance and significantly decreased lung metastasis, and both metabolites reduced Ki-67, cyclin D1, and ErbB2 levels in tumors. Perfusion with 25(OH)D caused a 50% raise in tumor 1,25(OH)2D levels, indicating good tumor penetration and effective activation. Importantly, in contrast with 1,25(OH)2D, perfusion with 25(OH)D did not cause hypercalcemia. In vitro treatment of cultured MMTV-PyMT mammary tumor cells with 25(OH)D inhibited proliferation, confirming local activation of the prohormone in this system. This study provides an in vivo demonstration in a non-immunodeficient model of spontaneous breast cancer that exogenous 25(OH)D delays neoplasia, tumor growth, and metastasis, and that its chemoprevention efficacy is not accompanied by hypercalcemia.

Targeting IL-6 and RANKL signaling inhibits prostate cancer growth in bone

In prostate cancer metastases to bone, cancer cell-derived cytokines stimulate RANKL expression by cells of the osteoblast lineage, which in turn activates osteoclastic bone resorption. However, it is unclear whether cells of the osteoblast lineage signal back to prostate cancer cells, and if so, whether such direct cross-talk can be targeted therapeutically. Using the human prostate cancer cell line, PC3, we identified two novel signalling pathways acting between cells of the osteoblast lineage and cancer cells. First, exposure to RANKL stimulated the expression and release of IL-6 by PC3 cells in vitro (which is known to promote RANKL expression by osteoblasts). Second, treatment of PC3 cells with IL-6 increased the expression of RANK, the cognate receptor of RANKL, and enhanced the RANKL-induced release of IL-6 by PC3 cells. Third, targeted disruption of IL-6 signaling with tocilizumab, a clinically available antibody against the human IL-6 receptor, inhibited skeletal tumor growth in vivo and reduced serum RANKL levels as well as RANK expression by PC3-derived bone tumors. Similar effects were achieved when RANK expression was knocked down in PC3 cells. In contrast, disruption of IL-6 or RANK/RANKL signalling had no effect on PC3 tumor growth in soft tissues, indicating that these signalling pathways act specifically within the bone microenvironment. In conclusion, prostate cancer cells and cells of the osteoblast lineage communicate via two inter-dependent signaling pathways, which through auto-amplification strongly enhance metastatic prostate cancer growth in bone. Both pathways may be targeted for effective therapeutic intervention.

Vitamin D intake, blood 25(OH)D levels, and breast cancer risk or mortality: a meta-analysis

Background:

Experimental studies suggest potential anti-carcinogenic properties of vitamin D against breast cancer risk, but the epidemiological evidence to date is inconsistent.

Methods:

We searched MEDLINE and EMBASE databases along with a hand search for eligible studies to examine the association between vitamin D status (based on diet and blood 25-hydroxyvitamin D (25(OH)D)) and breast cancer risk or mortality in a meta-analysis. A random-effect model was used to calculate a pooled adjusted relative risk (RR).

Results:

A total of 30 prospective studies (nested case-control or cohort) were included for breast cancer incidence (n=24 studies; 31 867 cases) or mortality (n=6 studies; 870 deaths) among 6092 breast cancer patients. The pooled RRs of breast cancer incidence for the highest vs the lowest vitamin D intake and blood 25(OH)D levels were 0.95 (95% CI: 0.88–1.01) and 0.92 (95% CI: 0.83–1.02), respectively. Among breast cancer patients, high blood 25(OH)D levels were significantly associated with lower breast cancer mortality (pooled RR=0.58, 95% CI: 0.40–0.85) and overall mortality (pooled RR=0.61, 95% CI: 0.48–0.79). There was no evidence of heterogeneity and publication bias.

Conclusions:

Our findings suggest that high vitamin D status is weakly associated with low breast cancer risk but strongly associated with better breast cancer survival.

Involvement of protease-activated receptor 2 in nociceptive behavior in a rat model of bone cancer

Treatment for bone cancer pain remains a clinical challenge due to a poor understanding of the underlying mechanisms. Protease-activated receptor 2 (PAR2), a receptor for inflammatory proteases, has been implicated in nociceptive signaling under both normal and pathologic pain states. However, little is known of the role of PAR2 in cancer-induced bone pain. Here we investigated the potential role of PAR2 in a rat model of bone cancer pain. The model of bone cancer pain was induced by inoculating Walker 256 into the tibia bone cavity of rats and verified by X-ray imaging, pathology, and behavior assessments. The rats with bone cancer exhibited marked mechanical allodynia, thermal hyperalgesia, and signs of spontaneous nocifensive behavior. Subcutaneous administration of the PAR2 antagonist FSLLRY-NH2 almost completely abolished mechanical allodynia and thermal hyperalgesia but had no effects on spontaneous pain behavior in the rats with bone cancer. Immunohistochemical study revealed that the expression of PAR2 was significantly increased in large- and medium-sized dorsal root ganglia (DRG) neurons but not in small-sized neurons after Walker 256 inoculation. These results suggest that the increased expression of PAR2 in the DRG may contribute to the development of mechanical allodynia and thermal hyperalgesia associated with bone cancer rats. PAR2 might become a novel target for the treatment of pain in patients with bone cancer.

Equivalent anticancer activities of dietary vitamin D and calcitriol in an animal model of breast cancer: importance of mammary CYP27B1 for treatment and prevention

Calcitriol [1,25(OH)2D3], the hormonally active form of vitamin D exerts anti-proliferative, pro-apoptotic, anti-inflammatory effects and other anticancer actions in breast cancer (BCa) cell cultures and animal models of BCa. Our research is focused on investigating the potential beneficial effects of dietary vitamin D3 compared to calcitriol and the underlying mechanisms in BCa treatment and chemoprevention. We recently found that dietary vitamin D3 exhibits significant tumor inhibitory effects in xenograft models of BCa that are equivalent to those elicited by the administration of the active hormone calcitriol. At the easily achievable dose tested in our studies, dietary vitamin D3 exhibited substantial tumor inhibitory activity and, unlike calcitriol, did not cause hypercalcemia demonstrating its relative safety. We found elevations in circulating calcitriol as well as increased CYP27B1 expression in the tumor and the intestine in tumor-bearing mice ingesting a vitamin D3-supplemented diet. We hypothesize that the elevation in circulating 25(OH)D induced by dietary vitamin D3 supplements stimulates local synthesis of calcitriol in the mammary tumor microenvironment and the ensuing paracrine/autocrine actions play a major role in the anticancer activity of dietary vitamin D3. Our findings suggest that the endocrine activity of calcitriol derived from tumor and other extra-renal sources such as the intestine, probably also plays a role in mediating the anticancer effects of dietary vitamin D3. Thus it appears that multiple sites of 1α-hydroxylation contribute to the anticancer effects of dietary vitamin D3. Our data strongly suggest that dietary vitamin D will be useful in the chemoprevention and treatment of BCa since it is a safe, economical and easily available nutritional agent that is equivalent to calcitriol in exerting anticancer effects, at least in mouse models. Furthermore, adequate vitamin D nutrition and avoidance of vitamin D deficiency appear to be important in reducing BCa risk. These findings warrant clinical trials in BCa patients and in women at high risk for BCa to evaluate the benefits of dietary vitamin D3 supplementation. This article is part of a Special Issue entitled 'Vitamin D Workshop'.

Associations of serum 25-hydroxyvitamin D with overall and breast cancer-specific mortality in a multiethnic cohort of breast cancer survivors

PURPOSE

Despite limited evidence on the association of vitamin D with outcomes in breast cancer survivors, some clinicians advise breast cancer patients to use vitamin D supplements. More evidence is needed to inform these recommendations.

METHODS

In the Health, Eating, Activity, and Lifestyle study, we examined associations of post-treatment serum concentrations of 25-hydroxyvitamin D (25(OH)D) on overall and breast cancer-specific mortality in 585 breast cancer survivors from western Washington State, New Mexico, and Los Angeles County. 25(OH)D was measured in stored blood collected 2 years post-enrollment. Outcomes were ascertained from the Surveillance, Epidemiology, and End Results registries and medical records. Cox proportional hazards models were fit to assess associations of serum 25(OH)D with overall and breast cancer-specific mortality.

RESULTS

After a median follow-up of 9.2 years; 110 women died, including 48 from breast cancer. Standard cut points classified 211 (31.6 %) women as serum 25(OH)D deficient (<20 ng/mL), 189 (32.2 %) as insufficient (20-30 ng/mL), and 185 (36.2 %) as sufficient (>30 ng/mL). Compared to women with deficient 25(OH)D, those in the sufficient ranges had a decreased risk of overall mortality (age-adjusted HR = 0.58; 95 % CI 0.36-0.96); however, multivariate adjustments attenuated the association (HR = 0.90; 95 % CI 0.50-1.61). No association was found between serum 25(OH)D and breast cancer-specific mortality (sufficient: HR = 1.21; 95 % CI 0.52-2.80) in multivariate models.

CONCLUSION

In this breast cancer cohort, higher serum 25(OH)D may be associated with improved survival, but results were not statistically significant and must be interpreted with caution. The potential prognostic effect of vitamin D from diet, supplements, or both should be evaluated in future larger studies with additional endpoints from breast cancer patients.

Vitamin D: metabolism, molecular mechanisms, and mutations to malignancies

The potential protective effects of vitamin D against cutaneous carcinogenesis are still poorly understood. The inhibition, by vitamin D, of various cancers in in vitro and in vivo models has triggered detailed investigation of vitamin D effects on neoplastic behavior. Recent studies highlight that such neoplastic features as the tumor microenvironment, angiogenesis, DNA mutagenesis, and apoptosis are all connected to vitamin D metabolic pathways. This review discusses these connections. Vitamin D modulation of the cell cycle, DNA repair and apoptosis via its receptors (VDRs) may have a suppressive effect on skin cancer as some studies suggest. The regulation of multiple tumor signaling pathways by vitamin D may have an implication in cutaneous carcinogenesis and tumor progression to malignancy.

The role of the bone microenvironment in skeletal metastasis

The bone microenvironment provides a fertile soil for cancer cells. It is therefore not surprising that the skeleton is a frequent site of cancer metastasis. It is believed that reciprocal interactions between tumour and bone cells, known as the “vicious cycle of bone metastasis” support the establishment and orchestrate the expansion of malignant cancers in bone. While the full range of molecular mechanisms of cancer metastasis to bone remain to be elucidated, recent research has deepened our understanding of the cell-mediated processes that may be involved in cancer cell survival and growth in bone. This review aims to address the importance of the bone microenvironment in skeletal cancer metastasis and discusses potential therapeutic implications of novel insights.

Effects of sangu decoction on osteoclast activity in a rat model of breast cancer bone metastasis

Bone metastasis (BM) is a major clinical problem for which current treatments lack full efficacy. The Traditional Chinese Medicine (TCM) Sangu Decoction (SGD) has been widely used to treat BM in China. However, no in vivo experiments to date have investigated the effects of TCM on osteoclast activity in BM. In this study, the protective effect and probable mechanism of SGD were evaluated. The model was established using the breast cancer MRMT-1 cells injected into the tibia of rat. SGD was administrated, compared with Zoledronic acid as a positive control. The development of the bone tumor and osteoclast activity was monitored by radiological analysis. TRAP stain was used to identify osteoclasts quantity and activity. TRAP-5b in serum or bone tumor and TRAP mRNA were also quantified. Radiological examination showed that SGD inhibited tumor proliferation and preserved the cortical and trabecular bone structure. In addition, a dramatic reduction of TRAP positive osteoclasts was observed and TRAP-5b levels in serum and bone tumor decreased significantly. It also reduced the mRNA expression of TRAP. The results indicated that SGD exerted potent antiosteoclast property that could be directly related to its TRAP inhibited activity. In addition it prevented bone tumor proliferation in BM model.

Extraskeletal effects of vitamin D

The presence of vitamin D receptors in diverse tissues like immune cells, beta-cells in the pancreas, and cardiac myocytes has prompted research to evaluate the impact of vitamin D deficiency on the occurrence of immune diseases, diabetes, and cardiovascular disease (CVD). The expression of receptors not only in normal cells, but also in cancer cells including breast, prostate, and colon cancer cells has moreover opened the path to therapeutic exploitation of vitamin D or its metabolites and hypocalcemic structural analogues as pharmaceutical tools in the fight against chronic non-communicable diseases like diabetes, CVD, and cancer.

Breast cancer proteome takes more than two to tango on TRAIL: beat them at their own game

Breast carcinogenesis is a multidimensional disease that has resisted drug-related solutions to date because of heterogeneity, disorganized spatiotemporal behavior of signal transduction cascades, cell cycle checkpoints, cell transition, plasticity, and impaired pro-apoptotic response. These synchronized oncogenic events, including protein-protein interaction, transcriptional-regulatory, and signaling networks, trigger genomic and transcriptional disturbances in TRAIL-mediated signaling network neighborhoods. Therefore, tumor cells often acquire the ability to escape death by suppressing cell death pathways that normally function to eliminate damaged and harmful cells. This review describes the TRAIL-mediated cell death signaling pathways, the interactions between these pathways, and the ways in which these pathways are deregulated in breast cancer.

Regulation of motility, invasion, and metastatic potential of squamous cell carcinoma by 1α,25-dihydroxycholecalciferol

BACKGROUND

The active metabolite of vitamin D 1α,25-dihydroxycholecalciferol (1,25D(3) ) has exhibited broad-spectrum antitumor activity in xenograft animal models. However, its activity against metastatic disease has not been extensively investigated.

METHODS

Squamous cell carcinoma (SCC) or 1,25D(3) -resistant variant SCC-DR cells were treated with 1,25D(3) . Actin organization was examined by immunofluorescence assay. Cell migration was assessed by "wound" healing and chemotactic migration assays. Cell invasion was assessed by a Matrigel-based invasion assay and in situ zymography. Matrix metalloproteinase 2 (MMP-2) and MMP-9 expression and secretion were examined by immunoblot analysis and an enzyme-linked immunosorbent assay, respectively. E-cadherin expression was assessed by flow cytometry, immunoblot analysis, and immunohistochemistry. Knockdown of E-cadherin was achieved by small interfering RNA. An experimental metastasis mouse model was created by intravenous injection of tumor cells; and lung tumor development in the mice was assessed by magnetic resonance imaging, gross observation, and histology.

RESULTS

SCC cellular morphology and actin organization were altered by 10 nM 1,25D(3) . 1,25D(3) inhibited SCC cell motility and invasion, which were associated with reduced expression and secretion of MMP-2 and MMP-9, and 1,25D(3) promoted the expression of E-cadherin. These findings were not observed in SCC-DR cells. Knock down of E-cadherin rescued 1,25D(3) -inhibited cell migration. Intravenous injection of SCC or SCC-DR cells resulted in the establishment of extensive pulmonary lesions in saline-treated C3H mice. Treatment with 1,25D(3) resulted in a marked reduction in the formation of lung tumor colonies in mice that were injected with SCC cells, but not in mice that were injected with SCC-DR cells.

CONCLUSIONS

1,25D(3) suppressed SCC cell motility, invasion, and metastasis, partially through the promotion of E-cadherin-mediated cell-cell adhesion.

Cellular and molecular effects of vitamin D on carcinogenesis

Epidemiologic data suggest that the incidence and severity of many types of cancer inversely correlates with indices of vitamin D status. The vitamin D receptor (VDR) is highly expressed in epithelial cells at risk for carcinogenesis including those resident in skin, breast, prostate and colon, providing a direct molecular link by which vitamin D status impacts on carcinogenesis. Consistent with this concept, activation of VDR by its ligand 1,25-dihydroxyvitamin D (1,25D) triggers comprehensive genomic changes in epithelial cells that contribute to maintenance of the differentiated phenotype, resistance to cellular stresses and protection of the genome. Many epithelial cells also express the vitamin D metabolizing enzyme CYP27B1 which enables autocrine generation of 1,25D from the circulating vitamin D metabolite 25-hydroxyvitamin D (25D), critically linking overall vitamin D status with cellular anti-tumor actions. Furthermore, pre-clinical studies in animal models has demonstrated that dietary supplementation with vitamin D or chronic treatment with VDR agonists decreases tumor development in skin, colon, prostate and breast. Conversely, deletion of the VDR gene in mice alters the balance between proliferation and apoptosis, increases oxidative DNA damage, and enhances susceptibility to carcinogenesis in these tissues. Because VDR expression is retained in many human tumors, vitamin D status may be an important modulator of cancer progression in persons living with cancer. Collectively, these observations have reinforced the need to further define the molecular actions of the VDR and the human requirement for vitamin D in relation to cancer development and progression.

Dietary vitamin D₃ and 1,25-dihydroxyvitamin D₃ (calcitriol) exhibit equivalent anticancer activity in mouse xenograft models of breast and prostate cancer

1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3) or calcitriol], the hormonally active vitamin D metabolite, exhibits anticancer actions in models of breast cancer and prostate cancer. Because CYP27B1 (1α-hydroxylase), the enzyme catalyzing 1,25(OH)(2)D(3) formation in the kidney, is also expressed in extrarenal tissues, we hypothesize that dietary vitamin D(3) will be converted to 25(OH)D(3) in the body and then to 1,25(OH)(2)D(3) locally in the cancer microenvironment in which it will exert autocrine/paracrine anticancer actions. Immunocompromised mice bearing MCF-7 breast cancer xenografts showed significant tumor shrinkage (>50%) after ingestion of a vitamin D(3)-supplemented diet (5000 IU/kg) compared with a control diet (1000 IU/kg). Dietary vitamin D(3) inhibition of tumor growth was equivalent to administered calcitriol (0.025, 0.05, or 0.1 μg/mouse, three times a week). Both treatments equivalently inhibited PC-3 prostate cancer xenograft growth but to a lesser extent than the MCF-7 tumors. Calcitriol at 0.05 μg and 0.1 μg caused modest but statistically significant increases in serum calcium levels indicating that the dietary vitamin D(3) comparison was to a maximally safe calcitriol dose. Dietary vitamin D(3) did not increase serum calcium, demonstrating its safety at the concentration tested. The vitamin D(3) diet raised circulating 1,25 dihydroxyvitamin D levels and did not alter CYP27B1 mRNA in the kidney but increased it in the tumors, suggesting that extrarenal sources including the tumors contributed to the elevated circulating 1,25 dihydroxyvitamin D(3). Both calcitriol and dietary vitamin D(3) were equipotent in suppressing estrogen synthesis and signaling and other proinflammatory and growth signaling pathways. These preclinical data demonstrate the potential utility of dietary vitamin D(3) supplementation in cancer prevention and therapy.

Does vitamin D protect against DNA damage?

Vitamin D is a secosteroid best known for its role in maintaining bone and muscle health. Adequate levels of vitamin D may also be beneficial in maintaining DNA integrity. This role of vitamin D can be divided into a primary function that prevents damage from DNA and a secondary function that regulates the growth rate of cells. The potential for vitamin D to reduce oxidative damage to DNA in a human has been suggested by clinical trial where vitamin D supplementation reduced 8-hydroxy-2'-deoxyguanosine, a marker of oxidative damage, in colorectal epithelial crypt cells. Studies in animal models and in different cell types have also shown marked reduction in oxidative stress damage and chromosomal aberrations, prevention of telomere shortening and inhibition of telomerase activity following treatment with vitamin D. The secondary function of vitamin D in preventing DNA damage includes regulation of the poly-ADP-ribose polymerase activity in the DNA damage response pathway involved in the detection of DNA lesions. It is also able to regulate the cell cycle to prevent the propagation of damaged DNA, and to regulate apoptosis to promote cell death. Vitamin D may contribute to prevention of human colorectal cancer, though there is little evidence to suggest that prevention of DNA damage mediates this effect, if real. Very limited human data mean that the intake of vitamin D required to minimise DNA damage remains uncertain.