Combined effect of vitamin D3 analogs and paclitaxel on the growth of MCF-7 breast cancer cells in vivo

Vitamin D3 Inhibits the Viability of Breast Cancer Cells In Vitro and Ehrlich Ascites Carcinomas in Mice by Promoting Apoptosis and Cell Cycle Arrest and by Impeding Tumor Angiogenesis

The incidence of aggressive and resistant breast cancers is growing at alarming rates, indicating a necessity to develop better treatment strategies. Recent epidemiological and preclinical studies detected low serum levels of vitamin D in cancer patients, suggesting that vitamin D may be effective in mitigating the cancer burden. However, the molecular mechanisms of vitamin D3 (cholecalciferol, vit-D3)-induced cancer cell death are not fully elucidated. The vit-D3 efficacy of cell death activation was assessed using breast carcinoma cell lines in vitro and a widely used Ehrlich ascites carcinoma (EAC) breast cancer model in vivo in Swiss albino mice. Both estrogen receptor-positive (ER+, MCF-7) and -negative (ER-, MDA-MB-231, and MDA-MB-468) cell lines absorbed about 50% of vit-D3 in vitro over 48 h of incubation. The absorbed vit-D3 retarded the breast cancer cell proliferation in a dose-dependent manner with IC50 values ranging from 0.10 to 0.35 mM. Prolonged treatment (up to 72 h) did not enhance vit-D3 anti-proliferative efficacy. Vit-D3-induced cell growth arrest was mediated by the upregulation of p53 and the downregulation of cyclin-D1 and Bcl2 expression levels. Vit-D3 retarded cell migration and inhibited blood vessel growth in vitro as well as in a chorioallantoic membrane (CAM) assay. The intraperitoneal administration of vit-D3 inhibited solid tumor growth and reduced body weight gain, as assessed in mice using a liquid tumor model. In summary, vit-D3 cytotoxic effects in breast cancer cell lines in vitro and an EAC model in vivo were associated with growth inhibition, the induction of apoptosis, cell cycle arrest, and the impediment of angiogenic processes. The generated data warrant further studies on vit-D3 anti-cancer therapeutic applications.

Combinations of Calcitriol with Anticancer Treatments for Breast Cancer: An Update

Preclinical, clinical, and epidemiological studies indicate that vitamin D3 (VD) deficiency is a risk factor for the development of breast cancer. Underlying mechanisms include the ability of calcitriol to induce cell differentiation, inhibit oncogenes expression, and modify different signaling pathways involved in the control of cell proliferation. In addition, calcitriol combined with different kinds of antineoplastic drugs has been demonstrated to enhance their beneficial effects in an additive or synergistic fashion. However, a recognized adjuvant regimen based on calcitriol for treating patients with breast cancer has not yet been fully established. Accordingly, in the present work, we review and discuss the preclinical and clinical studies about the combination of calcitriol with different oncological drugs, aiming to emphasize its main therapeutic benefits and opportunities for the treatment of this pathology.

Effect of vitamin D on malignant behavior of non-small cell lung cancer cells

OBJECTIVE

To investigate the effects of vitamin D on the malignant behavior of A549 and NCI-H1975 tumor cells (proliferation, apoptosis, invasion, metastasis and drug resistance-related proteins) and the activation of the PI3K/AKT/mTOR signaling pathway, in order to evaluate the effect of vitamin D on the therapeutic action of cisplatin.

METHOD

In vitro cell experiments, CCK-8, flow cytometry, transwell, scratches, MTT and Western blot were used to reveal the effect of vitamin D on non-small cell lung cancer (NSCLC), and the expression of PI3K/AKT/mTOR signaling pathway was also detected. In vivo animal experiments, the nude mice were divided into four groups: control group, vitamin D treatment group, cisplatin treatment group and vitamin D + cisplatin combined treatment group. After tumor formation in vitro, tumor volume changes were calculated and tumor growth curves were drawn, collected tumor tissues for pathological sections. Western blot was used to detect the expression changes of drug-resistance related proteins in tumor tissues. Meanwhile, protein expression changes of PI3K/AKT/mTOR signaling pathway in tumor tissues were detected.

RESULT

In vitro experiments confirm Vitamin D can inhibit the proliferation, invasion and metastasis of non-small cell lung cancer cells A549 and NCI-H1975, promoting cell apoptosis, up-regulate the sensitivity of chemotherapy drugs. These effects of vitamin D may be correlated with the PI3K/AKT/mTOR signaling pathway. In vivo animal experiments, the changes in tumor volume, tumor inflammatory infiltration range, expression of drug-resistant related proteins and signaling pathway related proteins in mice were as follows: The vitamin D and cisplatin combined treatment group was significantly smaller than the control group.

CONCLUSION

Vitamin D can inhibit the proliferation, invasion and metastasis of non-small cell lung cancer (NSCLC) cells A549 and NCI-H1975 and promote apoptosis, up-regulate the sensitivity of chemotherapy drugs. The effect of vitamin D on NSCLC cells A549 and NCI-H1975 was correlated with the PI3K/AKT/mTOR signaling pathway. Vitamin D also promotes the therapeutic effect of CDDP.

Calcitriol-Loaded Dual-pH-Sensitive Micelle Counteracts Pro-Metastasis Effect of Paclitaxel in Triple-Negative Breast Cancer Therapy

The therapy of triple-negative breast cancer (TNBC) relies on chemotherapy basing on cytotoxic agents, including paclitaxel (PTX). Unfortunately, PTX will facilitate the invasion of cancer cells and the formation of metastases. To counteract pro-metastasis of PTX in TNBC therapy, in this work, calcitriol (CTL) is delivered along with PTX by a dual-pH-sensitive micelle. The PTX/CTL-co-loaded dual-pH-sensitive micelle (PCDM) can switch its surface charge from negative to positive at the tumor tissue and release PTX and CTL inside the lysosomes because of the structure change of the polymers composing PCDM under the acidic condition. This property makes PCDM able to escape from mononuclear-phagocyte system clearance and easy to enter tumor cells. PCDM efficiently suppresses the 4T1 primary tumor growth in mice and inhibits lung metastasis, due to downregulation of matrix metalloproteinase-9 and BCL-2 levels, upregulation of E-cadherin level, and counteracting the PTX-induced elevation of C-C motif chemokine ligand 2 (CCL2) and Ly6C⁺ monocytes levels by CTL. PCDM shows good biocompatibility without promoting the serum calcium level. Therefore, the combination of PTX and CTL based on this pH-sensitive micelle is promising for the TNBC treatment.

Evaluating Inhibitory Effects of Paclitaxel and Vitamin D3 Loaded Poly Lactic Glycolic Acid Co-Delivery Nanoparticles on the Breast Cancer Cell Line

Purpose: Paclitaxel (PTX) has transpired as a significant agent in the treatment of breast cancer. Meanwhile, polylactic glycolic acid (PLGA) nanoparticles (NPs) are able to increase the anticancer effect of the PTX in the blood.

Methods: Nano-precipitation was used to prepare the PLGA-PTX-VitD3 co-delivery NPs. Drug loading, encapsulation efficiency, in vitro release profile, cell viability, migration, apoptosis, and bcl2 expression of NPs were evaluated.

Results: The average size of co-delivery NPs was 231 ± 46 nm. Observed was a controlled release of the PTX and vitamin D3 from co-delivery NPs between 0.5 and 240 hours. MTT showed the ability of 8 μg.mL-1 of co-delivery NPs to kill 50 % of the MCF-7; likewise, the co-delivery NPs prevented MCF-7 migration. The co-delivery NPs led 46.35 % MCF-7 to enter primary apoptosis. 60.8% of MCF-7 in the control group were able to enter the G (1) phase of the cell cycle. The co-delivery NPs increased expression of bax. In addition to its higher toxicity against MCF-7 than that of PTX, co-delivery NPs were able to release drugs continuously for a long period, which indeed increased the efficiency of the drugs.

Conclusion: The effect of co-delivery NPs on MCF-7 cell viability was different from that in other drugs. In fact, the co-deliver NPs were able to release drugs continuously for a long time, this could induce primary apoptosis in the MCF-7 and decrease the metastasis and toxicity of drugs.

Serum Vitamin D Levels Affect Pathologic Complete Response in Patients Undergoing Neoadjuvant Systemic Therapy for Operable Breast Cancer

INTRODUCTION

There has been increasing interest in the potential benefit of vitamin D in improving breast cancer outcome. Preclinical studies suggest that vitamin D enhances chemotherapy-induced cell death. We investigated the impact of serum vitamin D levels during neoadjuvant chemotherapy (NAC) on the rates of achieving pathologic complete response (pCR) after breast cancer NAC.

PATIENTS AND METHODS

Patients from 1 of 2 Iowa registries who had serum vitamin D level measured before or during NAC were included. French patients enrolled onto a previous study of the impact of NAC on vitamin D and bone metabolism were also eligible for this study. Vitamin D deficiency was defined as < 20 ng/mL. pCR was defined as no residual invasive disease in breast and lymph nodes. A Firth penalized logistic regression multivariable model was used.

RESULTS

The study included 144 women. There was no difference between the French and Iowan cohorts with regard to age at diagnosis (P = .20), clinical stage (P = .22), receptor status (P = .32), and pCR rate (P = .34). French women had lower body mass index (mean 24.8 vs. 28.8, P < .01) and lower vitamin D levels (mean 21.5 vs. 27.5, P < .01) compared to Iowan patients. In multivariable analysis, after adjusting for the effects of cohort, clinical stage, and receptor status, vitamin D deficiency increased the odds of not attaining pCR by 2.68 times (95% confidence interval, 1.12-6.41, P = .03).

CONCLUSION

Low serum vitamin D levels were associated with not attaining a pCR. Prospective trials could elucidate if maintaining vitamin D levels during NAC, a highly modifiable variable, may be utilized to improve cancer outcomes.

The roles of UVB and vitamin D in reducing risk of cancer incidence and mortality: A review of the epidemiology, clinical trials, and mechanisms

Global cancer incidence and mortality rates are high and increasing. Thus, it is imperative to find novel solutions to preventing cancer incidence and treating it at an affordable yet efficacious manner. The solar UVB-vitamin D-cancer hypothesis was first proposed in 1980 based on a geographical ecological study. Since then, numerous ecological and observational studies as well as studies of mechanisms have provided support for the hypothesis. However, observational studies have not provided consistent support, in part due to using a single blood draw from any season to use for serum 25-hydroxyvitamin D [25(OH)D] concentration in prospective studies with long follow-up times. Case-controls studies, in which blood is drawn near time of diagnosis, and prospective studies in which blood is drawn in the sunnier half of the year, are more likely to find significant inverse relations between 25(OH)D and cancer incidence. Three vitamin D plus calcium clinical trials have found significant reduction in all-cancer incidence. This paper reviews the evidence for vitamin D in reducing incidence of and increasing survival from breast, colorectal, lung, ovarian, pancreatic, and prostate cancer. The epidemiological evidence provides strong support for all of these types of cancer except for non-aggressive prostate cancer. Studies of the cellular mechanisms of vitamin D action in different cancer cell types, strongly indicate that vitamin D can exert protective and anti-tumorigenic activities that would retard cellular transformation, hyperplasia and cancer progression. Based on the scientific evidence reviewed in this paper, individuals and health providers can consider increasing 25(OH)D concentrations through sensible sun exposure and/or vitamin D supplementation to reduce risk of and, in conjunction with standard care, treat cancer. Public health acceptance of vitamin D for cancer prevention and treatment requires stronger support from vitamin D clinical trials.

Vitamin D3-dependent VDR signaling delays ron-mediated breast tumorigenesis through suppression of β-catenin activity

The Ron receptor is upregulated in human breast cancers and correlates with enhanced metastasis and reduced patient survival. Ron overexpression drives mammary tumorigenesis through direct β-catenin activation and augmented tumor cell proliferation, migration and invasion. Ron and β-catenin are also coordinately elevated in breast cancers. The vitamin D receptor (VDR) antagonizes β-catenin signaling. Herein, we examined mammary tumor onset and progression using a Ron-driven murine model of breast tumorigenesis crossed with VDR deficient mice. VDR ablation accelerated mammary tumor onset and led to tumors that exhibited a desmoplastic phenotype and enhanced metastases. Tumor levels of active β-catenin were markedly increased in the absence of VDR. In vitro, VDR activation in breast cancer cells reduced β-catenin activation and transcriptional activity leading to elevated expression of the extracellular Wnt inhibitor dickkopf-related protein 1, and a reduction in the interaction of β-catenin with the cyclin D1 promoter. Expression of a stabilized form or β-catenin ablated the protective effects of VDR activation. Collectively, these studies delineate a protective role for VDR signaling in Ron-induced mammary tumorigenesis through disruption of β-catenin activation.

The Vitamin D Analog, MART-10, Attenuates Triple Negative Breast Cancer Cells Metastatic Potential

Regarding breast cancer treatment, triple negative breast cancer (TNBC) is a difficult issue. Most TNBC patients die of cancer metastasis. Thus, to develop a new regimen to attenuate TNBC metastatic potential is urgently needed. MART-10 (19-nor-2α-(3-hydroxypropyl)-1α,25(OH)₂D₃), the newly-synthesized 1α,25(OH)₂D₃ analog, has been shown to be much more potent in cancer growth inhibition than 1α,25(OH)₂D₃ and be active in vivo without inducing obvious side effect. In this study, we demonstrated that both 1α,25(OH)₂D₃ and MART-10 could effectively repress TNBC cells migration and invasion with MART-10 more effective. MART-10 and 1α,25(OH)₂D₃ induced cadherin switching (upregulation of E-cadherin and downregulation of N-cadherin) and downregulated P-cadherin expression in MDA-MB-231 cells. The EMT(epithelial mesenchymal transition) process in MDA-MB-231 cells was repressed by MART-10 through inhibiting Zeb1, Zeb2, Slug, and Twist expression. LCN2, one kind of breast cancer metastasis stimulator, was also found for the first time to be repressed by 1α,25(OH)₂D₃ and MART-10 in breast cancer cells. Matrix metalloproteinase-9 (MMP-9) activity was also downregulated by MART-10. Furthermore, F-actin synthesis in MDA-MB-231 cells was attenuated as exposure to 1α,25(OH)₂D₃ and MART-10. Based on our result, we conclude that MART-10 could effectively inhibit TNBC cells metastatic potential and deserves further investigation as a new regimen to treat TNBC.

Inhibition of Mouse Breast Tumor-Initiating Cells by Calcitriol and Dietary Vitamin D

The anticancer actions of vitamin D and its hormonally active form, calcitriol, have been extensively documented in clinical and preclinical studies. However, the mechanisms underlying these actions have not been completely elucidated. Here, we examined the effect of dietary vitamin D and calcitriol on mouse breast tumor-initiating cells (TICs, also known as cancer stem cells). We focused on MMTV-Wnt1 mammary tumors, for which markers for isolating TICs have previously been validated. We confirmed that these tumors expressed functional vitamin D receptors and estrogen receptors (ER) and exhibited calcitriol-induced molecular responses including ER downregulation. Following orthotopic implantation of MMTV-Wnt1 mammary tumor cells into mice, calcitriol injections or a vitamin D-supplemented diet caused a striking delay in tumor appearance and growth, whereas a vitamin D-deficient diet accelerated tumor appearance and growth. Calcitriol inhibited TIC tumor spheroid formation in a dose-dependent manner in primary cultures and inhibited TIC self-renewal in secondary passages. A combination of calcitriol and ionizing radiation inhibited spheroid formation more than either treatment alone. Further, calcitriol significantly decreased TIC frequency as evaluated by in vivo limiting dilution analyses. Calcitriol inhibition of TIC spheroid formation could be overcome by the overexpression of β-catenin, suggesting that the inhibition of Wnt/β-catenin pathway is an important mechanism mediating the TIC inhibitory activity of calcitriol in this tumor model. Our findings indicate that vitamin D compounds target breast TICs reducing tumor-initiating activity. Our data also suggest that combining vitamin D compounds with standard therapies may enhance anticancer activity and improve therapeutic outcomes.

Vitamin D in cancer chemoprevention

CONTEXT

There is increasing evidence that Vitamin D (Vit D) and its metabolites, besides their well-known calcium-related functions, may also exert antiproliferative, pro-differentiating, and immune modulatory effects on tumor cells in vitro and may also delay tumor growth in vivo.

OBJECTIVE

The aim of this review is to provide fresh insight into the most recent advances on the role of Vit D and its analogues as chemopreventive drugs in cancer therapy.

METHODS

A systematic review of experimental and clinical studies on Vit D and cancer was undertaken by using the major electronic health database including ISI Web of Science, Medline, PubMed, Scopus and Google Scholar.

RESULTS AND CONCLUSION

Experimental and clinical observations suggest that Vit D and its analogues may be effective in preventing the malignant transformation and/or the progression of various types of human tumors including breast cancer, prostate cancer, colorectal cancer, and some hematological malignances. These findings suggest the possibility of the clinical use of these molecules as novel potential chemopreventive and anticancer agents.

Epigenetic regulation of vitamin D metabolism in human lung adenocarcinoma

INTRODUCTION

1α,25-Dihydroxyvitamin D3 (1,25-D3) is antiproliferative in preclinical models of lung cancer, but in tumor tissues, its efficacy may be limited by CYP24A1 expression. CYP24A1 is the rate limiting catabolic enzyme for 1,25-D3 and is overexpressed in human lung adenocarcinoma (AC) by unknown mechanisms.

METHODS

The DNA methylation status of CYP24A1 was determined by bisulfite DNA pyrosequencing in a panel of 30 lung cell lines and 90 surgically resected lung AC. The level of CYP24A1 methylation was correlated with CYP24A1 expression in lung AC cell lines and tumors. In addition, histone modifications were assessed by quantitative chromatin immunoprecipitation-polymerase chain reaction (ChIP-qPCR) in A549, NCI-H460, and SK-LU-1.

RESULTS

Bisulfite DNA pyrosequencing analysis revealed that CYP24A1 gene was heterogeneously methylated in lung AC. Expression of CYP24A1 was inversely correlated with promoter DNA methylation in lung AC cell lines and tumors. Treatment with 5-aza-2'-deoxycytidine (5-Aza) and trichostatin A (TSA) increased CYP24A1 expression in lung AC. We observed that CYP24A1 promoter hypermethylation decreased CYP24A1 enzyme activity in vitro, whereas treatment with 5-Aza and/or TSA increased CYP24A1 enzyme affinity for its substrate 1,25-D3. In addition, ChIP-qPCR analysis revealed specific histone modifications within the CYP24A1 promoter region. Treatment with TSA increased H3K4me2 and H3K9ac and simultaneously decreased H3K9me2 at the CYP24A1 promoter and treatment with 5-Aza and/or TSA increased the recruitment of vitamin D receptor (VDR) to vitamin D response elements (VDRE) of the CYP24A1 promoter.

CONCLUSIONS

The expression of CYP24A1 gene in human lung AC is in part epigenetically regulated by promoter DNA methylation and repressive histone modifications. These findings should be taken into consideration when targeting CYP24A1 to optimize antiproliferative effects of 1,25-D3 in lung AC.

Improved clinical outcomes associated with vitamin D supplementation during adjuvant chemotherapy in patients with HER2+ nonmetastatic breast cancer

BACKGROUND

Vitamin D (VD) supplementation has pleiotropic effects that extend beyond their impact on bone health, including the disruption of downstream VD receptor signaling and human epidermal growth factor receptor 2 (HER2) signaling through the ErbB2/AKT/ERK pathway. In the present study, we examined our institutional experience with patients having nonmetastatic HER2-positive (HER(+)) breast cancer and hypothesized that those patients who received VD supplementation during neoadjuvant chemotherapy would have improved long-term outcomes.

PATIENTS AND METHODS

We performed a retrospective review of all patients (n = 308) given trastuzumab-based chemotherapy between 2006 and 2012 at the University of Miami/Sylvester Comprehensive Cancer Center (UM/SCCC). We identified 2 groups of patients for comparison-those who received VD supplementation during neoadjuvant chemotherapy (n = 134) and those who did not (n = 112). Univariate and multivariate Cox proportional hazard regression models were fitted to overall survival (OS) and disease-free survival (DFS).

RESULTS

More than half of the patients received VD during neoadjuvant chemotherapy (54.5%), with 60% receiving a dose < 10,000 units/wk and 33.3% having a VD deficiency at the start of therapy. In our final multivariate model, VD use was associated with improved DFS (hazard ratio [HR], 0.36; 95% confidence interval [CI], 0.15-0.88; P = .026], whereas larger tumor size was associated with worse DFS (HR, 3.52; 95% CI, 1.06-11.66; P = .04). There were no differences in OS based on any of the categories, including VD use, tumor size, number of metastatic lymph nodes, age at diagnosis, or lymphovascular invasion (LVI).

CONCLUSION

VD supplementation in patients with nonmetastatic HER2(+) breast cancer is associated with improved DFS.

Retinoic acid therapy resistance progresses from unilineage to bilineage in HL-60 leukemic blasts

Emergent resistance can be progressive and driven by global signaling aberrations. All-trans retinoic acid (RA) is the standard therapeutic agent for acute promyelocytic leukemia, but 10-20% of patients are not responsive, and initially responsive patients relapse and develop retinoic acid resistance. The patient-derived, lineage-bipotent acute myeloblastic leukemia (FAB M2) HL-60 cell line is a potent tool for characterizing differentiation-induction therapy responsiveness and resistance in t(15;17)-negative cells. Wild-type (WT) HL-60 cells undergo RA-induced granulocytic differentiation, or monocytic differentiation in response to 1,25-dihydroxyvitamin D3 (D3). Two sequentially emergent RA-resistant HL-60 cell lines, R38+ and R38-, distinguishable by RA-inducible CD38 expression, do not arrest in G1/G0 and fail to upregulate CD11b and the myeloid-associated signaling factors Vav1, c-Cbl, Lyn, Fgr, and c-Raf after RA treatment. Here, we show that the R38+ and R38- HL-60 cell lines display a progressive reduced response to D3-induced differentiation therapy. Exploiting the biphasic dynamic of induced HL-60 differentiation, we examined if resistance-related defects occurred during the first 24 h (the early or "precommitment" phase) or subsequently (the late or "lineage-commitment" phase). HL-60 were treated with RA or D3 for 24 h, washed and retreated with either the same, different, or no differentiation agent. Using flow cytometry, D3 was able to induce CD38, CD11b and CD14 expression, and G1/G0 arrest when present during the lineage-commitment stage in R38+ cells, and to a lesser degree in R38- cells. Clustering analysis of cytometry and quantified Western blot data indicated that WT, R38+ and R38- HL-60 cells exhibited decreasing correlation between phenotypic markers and signaling factor expression. Thus differentiation induction therapy resistance can develop in stages, with initial partial RA resistance and moderate vitamin D3 responsiveness (unilineage maturation block), followed by bilineage maturation block and progressive signaling defects, notably the reduced expression of Vav1, Fgr, and c-Raf.

Pretreatment vitamin D level and response to neoadjuvant chemotherapy in women with breast cancer on the I-SPY trial (CALGB 150007/150015/ACRIN6657)

Laboratory studies suggest that vitamin D (vitD) enhances chemotherapy-induced cell death. The objective of this study was to determine whether pretreatment vitD levels were associated with response to neoadjuvant chemotherapy (NACT) in women with breast cancer. Study patients (n = 82) were enrolled on the I-SPY TRIAL, had HER2-negative tumors, and available pretreatment serum. VitD levels were measured via DiaSorin radioimmunoassay. The primary outcome was pathologic residual cancer burden (RCB; dichotomized 0/1 vs. 2/3). Secondary outcomes included biomarkers of proliferation, differentiation, and apoptosis (Ki67, grade, Bcl2, respectively) and 3-year relapse-free survival (RFS). Mean and median vitD values were 22.7 ng/mL (SD 11.9) and 23.1 ng/mL, respectively; 72% of patients had levels deemed “insufficient” (<30 ng/mL) by the Institute of Medicine (IOM). VitD level was not associated with attaining RCB 0/1 after NACT (univariate odds ratio [OR], 1.01; 95% CI, 0.96–1.05) even after adjustment for hormone receptor status (HR), grade, Ki67, or body mass index (BMI). Lower vitD levels were associated with higher tumor Ki67 adjusting for race (OR, 0.95; 95% CI, 0.90–0.99). VitD level was not associated with 3-year RFS, either alone (hazard ratio [HzR], 0.98; 95% CI, 0.95–1.02) or after adjustment for HR, grade, Ki-67, BMI, or response. VitD insufficiency was common at the time of breast cancer diagnosis among women who were candidates for NACT and was associated with a more proliferative phenotype. However, vitD levels had no impact on tumor response to NACT or short-term prognosis.

Oral paricalcitol (19-nor-1,25-dihydroxyvitamin D2) in women receiving chemotherapy for metastatic breast cancer: a feasibility trial

The vitamin D hormone, [1,25(OH) 2D, calcitriol], inhibits proliferation and angiogenesis in breast cancer but its therapeutic use is limited by hypercalcemia. Synthetic analogs of 1,25(OH) 2D that are less calcemic, such as paricalcitol (19-nor-1,25-Dihydroxyvitamin D 2), are used to treat hyperparathyroidism associated with chronic kidney disease. We sought to determine the safety and feasibility of taking oral paricalcitol with taxane-based chemotherapy in women with metastatic breast cancer (MBC). Oral paricalcitol was considered safe if it did not result in excessive toxicity, defined as grade 3 or higher serum calcium levels. It was considered feasible if the majority of women could take eight weeks of continuous therapy in the first three months. Serum calcium was monitored weekly and the paricalcitol dose was adjusted based on its calcemic effect. Intact parathyroid hormone (iPTH) was monitored as a marker of paricalcitol activity. Twenty-four women with MBC were enrolled. Twenty women (83%) received eight weeks of continuous therapy. Paricalcitol was well-tolerated with no instances of hypercalcemia grade 2 or greater. Fourteen women (54%) were able to escalate the dose. The dose range of paricalcitol in the first 3 mo was 2-7 ug/day. Serum iPTH levels at baseline were significantly higher in women with serum 25-Hydroxyvitamin D (25-OHD) levels less than 30 ng/ml (96.4 ± 40.9 pg/ml) vs. 46.2 ± 20.3 pg/ml (p = 0 0.001) (iPTH reference 12-72 pg/ml). We conclude that paricalcitol is safe and feasible in women with MBC who are receiving chemotherapy.

MART-10, a less calcemic vitamin D analog, is more potent than 1α,25-dihydroxyvitamin D3 in inhibiting the metastatic potential of MCF-7 breast cancer cells in vitro

With the recent advance in breast cancer therapy, the survival rate of breast cancer patients has improved greatly. In spite of the progress, 25-50% of breast cancer patients eventually will develop metastasis. Due to limited early detection methods, metastasis is usually diagnosed at the late stages beyond recovery likely due to resistance to currently available breast cancer therapies. Thus, a new strategy to prevent cancer cell growth and repress tumor metastasis is desirable. The active form of vitamin D3, 1α,25-dihydroxyvitamin D3 [1α,25(OH)2D3], has anti-invasion and anti-migration properties in pre-clinical studies, yet its clinical application has been hampered by its hypercalcemic side effect. Previously, we have demonstrated that a new class of less-calcemic vitamin D analog, 19-nor-2α-(3-hydroxypropyl)-1α,25-dihydroxyvitamin D3 (MART-10), is 1000-fold more active than 1α,25(OH)2D3 in suppressing MCF-7 cells growth through cell cycle arrest and apoptosis induction. In the current study, we show for the first time that MART-10 is more active than 1α,25(OH)2D3 in preventing MCF-7 cell invasion and migration likely mediated through the upregulation of E-cadherin, and the downregulation of Snail, Slug, and Twist, the transcription factors implicated in epithelial-mesenchymal transition (EMT), as well as MMP-13. Based on the current in vitro and the highly anti-tumor characteristics of MART-10 in a pancreatic xenograft model, MART-10 is deemed as a promising candidate for breast cancer treatment. Further in vivo animal study comparing MART-10 with 1α,25(OH)2D3 and other potent and less calcemic analogs of vitamin D is warranted.

26,26,26,27,27,27-Hexadeuterated-1,25-Dihydroxyvitamin D3 (1,25D-d6) As Adjuvant of Chemotherapy in Breast Cancer Cell Lines

It has been demonstrated that 1,25-dihydroxyvitamin D₃ (1,25D) and some of its analogues have antitumor activity. 1,25D labeled with deuterium (26,26,26,27,27,27-hexadeuterated 1α,25-dihydroxyvitamin D₃, or 1,25D-d₆) is commonly used as internal standard for 1,25D liquid chromatography-mass spectrometry (LC-MS) quantification. In the present study using human breast cancer cell lines, the biological activity of 1,25D-d₆ administered alone and in combination with two commonly used antineoplastic agents, 5-fluorouracil and etoposide, was evaluated. Using an MTT assay, flow cytometry, and western blots, our data demonstrated that 1,25D-d₆ has effects similar to the natural hormone on cell proliferation, cell cycle, and apoptosis. Furthermore, the combination of 1,25D-d₆ and etoposide enhances the antitumoral effects of both compounds. Interestingly, the antitumoral effect is higher in the more aggressive MDA-MB-231 breast cancer cell line. Our data indicate that 1,25D-d₆ administered alone or in combination with chemotherapy could be a good experimental method for accurately quantifying active 1,25D levels in cultures or in biological fluids, on both in vitro breast cancer cell lines and in vivo animal experimental models.

[Vitamin D and breast cancer: physiopathology, biological and clinical implications]

There is a recent increase in interest of vitamin D and breast cancer, facing the number of publications on the subject. This increase have several reasons, on the one hand, vitamin D deficiency is more and more prevalent and, on the other hand, there are new data that highlights the extra-bone effects of vitamin D, especially in breast cancer, the vitamin D is involved in the breast cancer risk factor, the prognosis, and the interaction with breast cancer treatments. This combination between vitamin D deficiency and breast cancer is extremely usual, and combined with all cancer clinical parameters: the incidence, the tumour biology, the clinical presentation, the prognosis, and the antineoplastic treatment tolerance. This vitamin D deficiency is increased after adjuvant cancer treatments. And yet, this problem increases bone metabolism disruptions in breast cancer patients, inducing osteoporotic risk at long time, even though this population is curable. This problem is therefore serious in the adjuvant breast cancer treatment. Unfortunately, in this population, the current recommendations are clearly insufficient, and the current randomized clinical trial results would contribute to define the best way to correct the vitamin D deficiency, quickly and secure.

Vitamin D in thyroid tumorigenesis and development

Besides its classical role in bone and calcium homeostasis, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), the active form of vitamin D, has many non-classical effects; antiproliferative, anti-apoptotic and prodifferentiating effects of 1,25(OH)2D3 have been described in several tumour types in preclinical models. This review focuses on the insights gained in the elucidation of the role of 1,25(OH)2D3 in the normal thyroid and in the pathogenesis, progression and treatment of thyroid cancer, the most common endocrine malignancy. An increasing amount of observations points towards a role for impaired 1,25(OH)2D3-VDR signalling in the occurrence and progression of thyroid cancer, and a potential for structural analogues in the multimodal treatment of dedifferentiated iodine-resistant thyroid cancer. A role for vitamin D in thyroid-related autoimmunity is less convincing and needs further study. Altered 1,25(OH)2D3-VDR signalling does not influence normal thyroid development nor thyrocyte function, but does affect C-cell function, at least in rodents. If these findings also apply to humans deserves further study.

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'.

Vitamin D and breast cancer: emerging concepts

The benefit of vitamin D in cancer prevention and to certain extent therapy has been well recognized. The active form of vitamin D, 1,25-dihydroxycholecalciferol (1,25(OH)2 D3) is a natural ligand for vitamin D receptor (VDR). Since 1,25(OH)2D3 exerts toxic effects at a concentration that is beneficial, nearly 1500 analogs of vitamin D have been synthesized and evaluated for their efficacy in a variety of carcinogenesis and human cancer models both in vitro and in vivo. Among these only a handful of them have been approved for evaluation in clinical trials for leukemia, breast, prostate and colon cancers. The mechanism of vitamin D action is mediated by the nuclear VDR and the signaling cascade for its action is extensively reported. In this review we focus on the newer concepts for vitamin D action. These include (1) differential effects of vitamin D in maintaining cell proliferation when the cells are under stress but suppressing cell growth when the cells are transformed; (2) functional significance of VDR polymorphism in potential vitamin D responsiveness; (3) regulation of constitutive splicing of vitamin D target gene, CYP24a, by the hormone and its significance; and (4) regulation of microRNA by vitamin D in breast cancer. It is anticipated that the new work in these selective areas would expand the understanding of vitamin D in breast cancer prevention and therapy.

Vitamin D and breast cancer: evidence for biological and clinical significance

SUMMARY Both vitamin D deficiency and breast cancer are common. Laboratory evidence strongly suggests a biological role for vitamin D in normal breast cellular maintenance. Clinically, however, definitive associations between vitamin D and breast cancer risk and outcome have been challenging to decipher. A myriad of epidemiological studies have attempted to connect vitamin D with breast cancer risk, stage at diagnosis and outcome, but results vary. Here, we will closely examine the biologic evidence that supports an association between vitamin D and breast cancer and summarize the epidemiologic and clinical studies in this area. We will discuss ongoing trials and additional research questions that should be addressed in future studies.

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.

Inhibitory effects of calcitriol on the growth of MCF-7 breast cancer xenografts in nude mice: selective modulation of aromatase expression in vivo

Calcitriol (1,25-dihydroxyvitamin D(3)), the hormonally active metabolite of vitamin D, exerts many anticancer effects in breast cancer (BCa) cells. We have previously shown using cell culture models that calcitriol acts as a selective aromatase modulator (SAM) and inhibits estrogen synthesis and signaling in BCa cells. We have now examined calcitriol effects in vivo on aromatase expression, estrogen signaling, and tumor growth when used alone and in combination with aromatase inhibitors (AIs). In immunocompromised mice bearing MCF-7 xenografts, increasing doses of calcitriol exhibited significant tumor inhibitory effects (~50% to 70% decrease in tumor volume). At the suboptimal doses tested, anastrozole and letrozole also caused significant tumor shrinkage when used individually. Although the combinations of calcitriol and the AIs caused a statistically significant increase in tumor inhibition in comparison to the single agents, the cooperative interaction between these agents appeared to be minimal at the doses tested. Calcitriol decreased aromatase expression in the xenograft tumors. Importantly, calcitriol also acted as a SAM in the mouse, decreasing aromatase expression in the mammary adipose tissue, while increasing it in bone marrow cells and not altering it in the ovaries and uteri. As a result, calcitriol significantly reduced estrogen levels in the xenograft tumors and surrounding breast adipose tissue. In addition, calcitriol inhibited estrogen signaling by decreasing tumor ERα levels. Changes in tumor gene expression revealed the suppressive effects of calcitriol on inflammatory and growth signaling pathways and demonstrated cooperative interactions between calcitriol and AIs to modulate gene expression. We hypothesize that cumulatively these calcitriol actions would contribute to a beneficial effect when calcitriol is combined with an AI in the treatment of BCa.

1,25-dihydroxyvitamin D3 and a superagonistic analog in combination with paclitaxel or suberoylanilide hydroxamic acid have potent antiproliferative effects on anaplastic thyroid cancer

Anaplastic thyroid cancer represents one of the most aggressive cancers. The active form of vitamin D, 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)), has been shown to have antiproliferative and/or redifferentiating properties in several malignancies, including thyroid cancer. The objective of this study was to investigate the effects of 1,25(OH)(2)D(3) and the superagonistic analog CD578 in anaplastic thyroid cancer, alone or in combination with paclitaxel, a taxane, and suberoylanilide hydroxamic acid (SAHA), a potent histone deacetylase inhibitor with promising effects in undifferentiated thyroid cancer. Four human thyroid cancer cell lines (FTC-133, C643, 8505C and HTh74) were treated with 1,25(OH)(2)D(3) or CD578, alone or in combination with paclitaxel or SAHA. Effects on cell growth and differentiation were evaluated. Clear effects on growth arrest were observed in a clonogenic assay, and absolute cell counts demonstrated a 24-36% reduction in all cell lines after 72h treatment with 1,25(OH)(2)D(3) (10(-6)M) and a 60% inhibition after 120h in the most sensitive cell line HTh74. A similar growth inhibition was shown after treatment with a 1000-fold lower concentration of analog CD578. This growth arrest was explained by antiproliferative effects, further supported by an increased % of cells in the G(0)-G(1) phase of the cell cycle and by a decreased transcription factor E2F1 mRNA expression. Combination treatments of 1,25(OH)(2)D(3) or CD578 with paclitaxel or SAHA resulted in an additive and in some conditions a synergistic effect on the inhibition of proliferation. Redifferentiation analysis revealed only a modest increase in sodium iodide symporter and thyroglobulin mRNA expression after treatment with 1,25(OH)(2)D(3), without additive effect after combination treatment. No effects were observed on TSH-receptor or thyroid peroxidase mRNA expression. Our in vitro findings demonstrate that the superagonistic vitamin D analog CD578 holds promise as adjuvant antiproliferative therapy of anaplastic thyroid cancer, especially in combination with other drugs such as paclitaxel or SAHA.

CYP24A1 is an independent prognostic marker of survival in patients with lung adenocarcinoma

PURPOSE

The active form of vitamin D, 1α,25-dihydroxyvitamin D(3) (1,25-D(3)), exerts antiproliferative effects in cancers, including lung adenocarcinoma (AC). CYP24A1 is overexpressed in many cancers and encodes the enzyme that catabolizes 1,25-D(3). The purpose of our study was to assess CYP24A1 as a prognostic marker and to study its relevance to antiproliferative activity of 1,25-D(3) in lung AC cells.

EXPERIMENTAL DESIGN

Tumors and corresponding normal specimens from 86 patients with lung AC (stages I-III) were available. Affymetrix array data and subsequent confirmation by quantitative real time-PCR were used to determine CYP24A1 mRNA expression. A subsequent validation set of 101 lung AC was used to confirm CYP24A1 mRNA expression and its associations with clinical variables. The antiproliferative effects of 1,25-D(3) were examined using lung cancer cell lines with high as well as low expression of CYP24A1 mRNA.

RESULTS

CYP24A1 mRNA was elevated 8- to 50-fold in lung AC (compared to normal nonneoplastic lung) and significantly higher in poorly differentiated cancers. At 5 years of follow-up, the probability of survival was 42% (high CYP24A1, n = 29) versus 81% (low CYP24A1, n = 57) (P = 0.007). The validation set of 101 tumors showed that CYP24A1 was independently prognostic of survival (multivariate Cox model adjusted for age, gender, and stage, P = 0.001). A549 cells (high CYP24A1) were more resistant to antiproliferative effects of 1,25-D(3) compared with SKLU-1 cells (low CYP24A1).

CONCLUSIONS

CYP24A1 overexpression is associated with poorer survival in lung AC. This may relate to abrogation of antiproliferative effects of 1,25-D(3) in high CYP24A1 expressing lung AC.

Vitamin D in combination cancer treatment

As a steroid hormone that regulates mineral homeostasis and bone metabolism, 1α, 25-dihydroxycholecalciferol (calcitriol) also has broad spectrum anti-tumor activities as supported by numerous epidemiological and experimental studies. Calcitriol potentiates the anti-tumor activities of multiple chemotherapeutics agents including DNA-damaging agents cisplatin, carboplatin and doxorubicin; antimetabolites 5-fluorouracil, cytarabine, hydroxyurea, cytarabine and gemcitabine; and microtubule-disturbing agents paclitaxel and docetaxel. Calcitriol elicits anti-tumor effects mainly through the induction of cancer cell apoptosis, cell cycle arrest, differentiation, angiogenesis and the inhibition of cell invasiveness by a number of mechanisms. Calcitriol enhances the cytotoxic effects of gamma irradiation and certain antioxidants and naturally derived compounds. Inhibition of calcitriol metabolism by 24-hydroxylase promotes growth inhibition effect of calcitriol. Calcitriol has been used in a number of clinical trials and it is important to note that sufficient dose and exposure to calcitriol is critical to achieve anti-tumor effect. Several trials have demonstrated that safe and feasible to administer high doses of calcitriol through intermittent regimen. Further well designed clinical trials should be conducted to better understand the role of calcitriol in cancer therapy.

Vitamin D analogs: therapeutic applications and mechanisms for selectivity

The vitamin D endocrine system plays a central role in mineral ion homeostasis through the actions of the vitamin D hormone, 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)], on the intestine, bone, parathyroid gland, and kidney. The main function of 1,25(OH)(2)D(3) is to promote the dietary absorption of calcium and phosphate, but effects on bone, kidney and the parathyroids fine-tune the mineral levels. In addition to these classical actions, 1,25(OH)(2)D(3) exerts pleiotropic effects in a wide variety of target tissues and cell types, often in an autocrine/paracrine fashion. These biological activities of 1,25(OH)(2)D(3) have suggested a multitude of potential therapeutic applications of the vitamin D hormone for the treatment of hyperproliferative disorders (e.g. cancer and psoriasis), immune dysfunction (autoimmune diseases), and endocrine disorders (e.g. hyperparathyroidism). Unfortunately, the effective therapeutic doses required to treat these disorders can produce substantial hypercalcemia. This limitation of 1,25(OH)(2)D(3) therapy has spurred the development of vitamin D analogs that retain the therapeutically important properties of 1,25(OH)(2)D(3), but with reduced calcemic activity. Analogs with improved therapeutic indices are now available for treatment of psoriasis and secondary hyperparathyroidism in chronic kidney disease, and research on newer analogs for these indications continues. Other analogs are under development and in clinical trials for treatment of various types of cancer, autoimmune disorders, and many other diseases. Although many new analogs show tremendous promise in cell-based models, this article will limit it focus on the development of analogs currently in use and those that have demonstrated efficacy in animal models or in clinical trials.

Vitamin D signalling pathways in cancer: potential for anticancer therapeutics

Epidemiological studies indicate that vitamin D insufficiency could have an aetiological role in various human cancers. Preclinical research indicates that the active metabolite of vitamin D, 1alpha,25(OH)2D3, also known as calcitriol, or vitamin D analogues might have potential as anticancer agents because their administration has antiproliferative effects, can activate apoptotic pathways and inhibit angiogenesis. In addition, 1alpha,25(OH)2D3 potentiates the anticancer effects of many cytotoxic and antiproliferative anticancer agents. Here, we outline the epidemiological, preclinical and clinical studies that support the development of 1alpha,25(OH)2D3 and vitamin D analogues as preventative and therapeutic anticancer agents.

Effective treatment of human breast tumor in a mouse xenograft model with herpes simplex virus type 1 specifying the NV1020 genomic deletion and the gBsyn3 syncytial mutation enabling high viral replication and spread in breast cancer cells

A new oncolytic and fusogenic herpes simplex virus type 1 (HSV-1) was constructed on the basis of the wildtype HSV-1(F) strain. To provide for safety and tumor selectivity, the virus carried a large deletion including one of the two alpha4, gamma(1)34.5, alpha0 genes and the latency-associated transcript region. The gamma(1)34.5 gene, a major neurovirulence factor, was replaced by a gene cassette constitutively expressing the red fluorescent protein gene. Homologous recombination was used to transfer the fusogenic gBsyn3 mutation to the viral genome to produce the OncSyn virus. OncSyn causes extensive virus-induced cell fusion (syncytia) and replicates to higher titers than the parental Onc and HSV-1(F) strains in breast cancer cells. Biochemical analysis revealed that the OncSyn virus retains a stable genome and expresses all major viral glycoproteins. A xenograft mouse model system using MDA-MB-435S-luc (MM4L) human breast cancer cells constitutively expressing the luciferase gene implanted within the interscapular region of animals was used to test the ability of the virus to inactivate breast tumor cells in vivo. Seventy-two mice bearing MM4L breast cancer xenografts were randomly divided into three groups and given two rounds of three consecutive intratumoral injections of OncSyn, inactivated OncSyn, or phosphate-buffered saline 3 days apart. A single round of virus injections resulted in a drastic reduction of tumor sizes (p <or= 0.0001) and diminution of chemiluminescence emitted by the cancer cells (p <or= 0.0002). This effect was enhanced by a second round of virus injections into the tumors 3 days after the first round (p <or= 0.0001). Systematic necropsy and pathological evaluation of the primary tumors revealed that the single round of injections resulted in extensive necrosis of tumor cells (p <or= 0.0001), which was enhanced by the second round of injections (p <or= 0.0002). Internal organs were not affected by virus inoculation. Mouse weights were not significantly impacted by any treatment during the course of the entire study (p = 0.46). These results show that the attenuated, fusogenic, and oncolytic HSV-1(F) virus strain OncSyn may effectively treat human breast tumors in vivo.

Vitamin D and cancer

1,25-dihydroxy Vitamin D [1,25-(OH)(2)D] exerts its effects via the vitamin D receptor (VDR) that belongs to the steroid/thyroid hormone receptor superfamily leading to gene regulation which results in various biological responses. Within the last two decades, the receptor has been shown to be present not only in classical target tissues such as bone, kidney and intestine but also in many other non-classical tissues. Besides the almost universal presence of VDRs, some cell types (e.g. keratinocytes, monocytes, bone, placenta) are capable of metabolizing 25-hydroxyvitamin D to 1,25(OH)(2)D by the enzyme 1alpha-hydroxylase (CYP27B1). The combined presence of 25(OH)D-1alpha-hydroxylase as well as the specific receptor in several tissues introduced the idea of a paracrine role for 1,25(OH)(2)D. Moreover, it has been demonstrated that 1,25(OH)(2)D can induce differentiation and inhibit proliferation of a wide variety of cell types. The molecular mechanisms behind this antiproliferative action is thoroughly explored but the whole picture is still difficult to understand. Important cell cycle regulators are involved such as cyclins, cyclin dependent kinases and their corresponding inhibitors as well as E2F transcription factors and accompanying pocket proteins. However the precise hierarchical structure of this wide diversity of actions of 1,25(OH)(2)D on genes influencing cell cycle progression is not firmly established nor do we understand which pathways are essential and which redundant. The antiproliferative action makes 1,25-(OH)(2)D and its analogs a possible therapeutic tool to treat hyperproliferative disorders, among which different types of cancer. This review focuses on the effects of 1,25(OH)(2)D and its analogs on cell proliferation, the results in in vivo experiments in Vitamin D deficient or resistant animals to cancer and the current epidemiological and intervention studies linking Vitamin D status or treatment and human cancer.

Promise of vitamin D analogues in the treatment of hyperproliferative conditions

1Alpha,25-dihydroxyvitamin D3 [1alpha,25-(OH)2D3; calcitriol] is best known as a hormone involved in calcium homeostasis but is also a potent antiproliferative agent in many cell types, particularly epithelial cells. 1Alpha,25(OH)2D3 mediates its actions through a classic steroid hormone-like transcriptional mechanism by influencing the expression of hundreds of genes. Effects of 1alpha,25(OH)2D3 have been observed on expression of cell cycle regulators, growth factors and their receptors, apoptotic machinery, metastatic potential, and angiogenesis; all of which have some effect on hyperproliferative conditions. This minireview focuses on the anticancer potential of 1alpha,25(OH)2D3 and its analogues by summarizing the promising data from animal and human trials of 1alpha,25(OH)2D3 and some of the more interesting synthetic vitamin D analogues in the treatment of a variety of different animal cancer models and in human patients with advanced cancer. Optimal administration of vitamin D analogues is only just being achieved with high-dose intermittent administration overcoming bioavailability and hypercalcemia problems and combination therapy with cytotoxic agents (taxols and cisplatins), antiresorptive agents (bisphosphonates), or cytochrome P450 inhibitors being attempted. Although the potential of vitamin D as an antiproliferative drug has been realized in the treatment of psoriasis and in parathyroid cell hyperplasia associated with secondary hyperparathyroidism, the search for an anticancer treatment incorporating a vitamin D analogue remains elusive.

Vitamin D2 analog (Paricalcitol; Zemplar) for treatment of myelodysplastic syndrome

Myelodysplastic syndrome (MDS) is often a pernicious disorder associated with pancytopenia in the elderly; therapeutic approaches need to balance their toxicities versus the symptoms of the disease. 1,25(OH)(2)-Vitamin-D(3) [1,25(OH)(2)D(3)] inhibits proliferation and induces differentiation of leukemic cells in vitro. Small clinical trials of 1,25(OH)(2)D(3) have shown modest efficacy in MDS; hypercalcemia prevented the administration of doses that have been shown to be effective in vitro. Paricalcitol [19-nor-1,25(OH)(2)D(2), Zemplar] has been approved by the FDA for treatment of secondary hyperparathyroidism. This Vitamin D analog is unique because it has little hypercalcemic potential; but in vitro, it has strong anti-leukemic activity. We conducted a clinical trial of oral paricalcitol to 12 MDS patients whose disease varied between an IPSS of low to high. Drug was well-tolerated in all patients. No responses were observed according to international working group (IWG) criteria. However, the platelet count of 1 of the 12 individuals rose from 53,500 to 120,000/microl blood over 5 weeks; but the patient succumbed to a fatal fungal infection. In summary, paricalcitol given as a single agent to MDS patients is therapeutically not very efficacious; further trials of the Vitamin D analog should be considered in combination with other approaches.

25-Hydroxyvitamin D3 1alpha-hydroxylase expression in breast cancer and use of non-1alpha-hydroxylated vitamin D analogue

Introduction

The cytochrome P450 mitochondrial enzyme 25-hydroxyvitamin D₃ 1α-hydroxylase (1α-hydroxylase) of renal tubule cells hydroxylates the major circulating form of vitamin D (25(OH)D₃) to the active systemic hormone 1,25(OH)₂D₃. Local production of 1,25(OH)₂D₃ appears to occur also at other sites where 1α-hydroxylase is expressed for autocrine/paracrine regulation. To reduce risks of hypercalcemia during treatment with vitamin D, we have previously suggested use of non-1α-hydroxylated vitamin D analogues to target tissues where 1α-hydroxylase is expressed, including the parathyroid glands in secondary hyperparathyroidism. The present study was undertaken to examine expression of 1α-hydroxylase in breast cancer and to investigate whether a non-1α-hydroxylated vitamin D analogue displayed biological function. In addition, expression of the 25-hydroxyvitamin D₃ 24-hydroxylase (24-hydroxylase) and the vitamin D receptor (VDR) was investigated.

Methods

The expression of 1α-hydroxylase, 24-hydroxylase and VDR was investigated in breast cancer specimens (n = 19) and normal breast tissues (n = 10) by immunohistochemistry and/or RT-PCR. Consecutive cryosections of 6 μm essentially free of immune cells were used in the analyses. The effect of vitamin D analogues on transcriptional activation was analyzed in transiently transfected MCF-7 breast cancer cells.

Results

1α-hydroxylase protein was demonstrated in 79% and 100% of breast cancer specimens and normal breast, respectively. The overall relative mRNA levels of 1α-hydroxylase and 24-hydroxylase in normal breast compared to breast tumors were: 1α-hydroxylase, 1 ± 0.07 versus 0.7 ± 0.05, respectively (p < 0.001); 24-hydroxylase, 1 ± 0.08 verus 2.1 ± 0.2, respectively (p < 0.001). The VDR was expressed in 95% of the tumors as expected, with mRNA levels of 1 ± 0.09 and 1.4 ± 0.12 (p < 0.05) in breast cancer and normal breast, respectively. The ketoconazole-sensitive transcription activation potential of the non-1α-hydroxylated vitamin D analogue prodrug of EB1089 (EB1285) was demonstrated in MCF-7 cells, which express 1α-hydroxylase. The activity of EB1285 was about 20% of 1,25(OH)₂D₃.

Conclusion

These results demonstrate nearly normal expression levels of 1α-hydroxylase, 24-hydroxylase and VDR in the majority of investigated breast cancer specimens. A non-1α-hydroxylated vitamin D analogue displayed activity in breast cancer cells. Such analogues may present future therapeutic options for proliferative disorders where 1α-hydroxylase is expressed.

EB1089, a vitamin D receptor agonist, reduces proliferation and decreases tumor growth rate in a mouse model of hormone-induced mammary cancer

1,25-Dihydroxyvitamin D3 and several of its analogs, such as EB1089, induce growth arrest and apoptosis of breast cancer cells in culture. EB1089 has also been shown to limit growth of xenografts in nude mice and carcinogen-induced mammary tumors in rats. Coupled with the fact that the vitamin D receptor is highly expressed in a large proportion of breast tumors, these data suggest that it may be a broad spectrum therapeutic target. We utilized a transgenic model of hormone-induced mammary cancer, the LH-overexpressing mouse, to assess, for the first time, the efficacy of EB1089 in a spontaneous tumor model. Similar to human breast cancers, the pre-neoplastic mammary glands and mammary tumors in these mice express high levels of vitamin D receptor. Treatment with EB1089 decreased proliferation of mammary epithelial cells in pre-neoplastic glands by 35%. Moreover, half of hormone-induced mammary tumors treated with EB1089 demonstrated a decreased rate of growth, with a subset of these tumors even regressing, suggesting that 1,25-dihydroxyvitamin D3 analogs may be effective chemopreventive and chemotherapeutic agents for breast cancer.

Enhancement by other compounds of the anti-cancer activity of vitamin D(3) and its analogs

Differentiation therapy holds promise as an alternative to cytotoxic drug therapy of cancer. Among compounds under scrutiny for this purpose is the physiologically active form of vitamin D(3), 1,25-dihydroxyvitamin D(3), and its chemically modified derivatives. However, the propensity of vitamin D(3) and its analogs to increase the levels of serum calcium has so far precluded their use in cancer patients except for limited clinical trials. This article summarizes the range of compounds that have been shown to increase the differentiation-inducing and antiproliferative activities of vitamin D(3) and its analogs, and discusses the possible mechanistic basis for this synergy in several selected combinations. The agents discussed include those that have differentiation-inducing activity of their own that is increased by combination with vitamin D(3) or analogs, such as retinoids or transforming growth factor-beta and plant-derived compounds and antioxidants, such as curcumin and carnosic acid. Among other compounds discussed here are dexamethasone, nonsteroidal anti-inflammatory drugs, and inhibitors of cytochrome P450 enzymes, for example, ketoconazole. Thus, recent data illustrate that there are extensive, but largely unexplored, opportunities to develop combinatorial, differentiation-based approaches to chemoprevention and chemotherapy of human cancer.

Effect of vitamin D analog (1alpha hydroxy D5) immunoconjugated to Her-2 antibody on breast cancer

We previously showed that a new vitamin D analog, 1alpha(OH)D5 (D5), induced differentiation and inhibited the growth of breast cancer cells. In this report, we examined whether D5 specifically delivered to breast cancer cells could have any therapeutic effect. D5 was linked to Her-2 antibody using sulfosuccinimidyl 6-4 azido nitrophenylamido hexanode (SANPAH) as a linker. The Her-2 antibody selected in our study had no significant effect on the in vitro or in vivo growth of breast cancer cells; however, it had cell-differentiating action. In vitro, D5-Her-2 antibody conjugate (IMC) showed the ability to specifically bind to Her-2-expressing cells, to compete with Her-2 antibody for surface receptor and to cause internalization. IMC (equivalent to 5 microg Her-2 antibody given intraperitoneally once weekly for 6 weeks) significantly inhibited the growth of BT-474 cells transplanted into athymic mice. The in vivo growth-inhibitory effect of IMC treatment was similar to that observed in animals receiving D5 continuously as a dietary supplement. These results show that the targeted delivery of D5 by immunoconjugation to cell surface receptor antibodies may be of potential therapeutic value for the treatment of Her-2 positive breast cancer.

Membrane disrupting lytic peptide conjugates destroy hormone dependent and independent breast cancer cells in vitro and in vivo

We have prepared conjugates of a membrane disrupting lytic peptide (hecate) and a 15-amino acid segment of the beta-chain of CG and hecate and the decapeptide, luteinizing hormone releasing hormone (LHRH). We have tested the concept that these conjugates will target breast cancer cells expressing LH/CG or LHRH receptors. In previous studies, we were able to destroy prostate cancers in vitro and in vivo with lytic peptide conjugates. Hecate, hecate-betaCG and LHRH-hecate were added to cultures of the human breast cancer cell lines MCF-7 and MDA-MB-435S. Hecate and its conjugates showed concentration dependent toxicity to both cell lines. The lytic peptide alone showed similar EC50 values for both cell lines; however, there was a significant difference between the EC50 values when the conjugates were tested. The hormone dependent MCF-7 cell line was less sensitive to the betaCG conjugate than to the LHRH conjugate; the reverse was found for the hormone independent MDA-MB-435S cells. Removal of steroids decreased the sensitivity of MCF-7 cells to both lytic peptide conjugates and this sensitivity could be restored by adding estradiol. Activation of protein kinase C further increased the sensitivity to the drug. MDA-MB-435S xenografts were established in intact female athymic nude mice, which were treated once a week for 3 weeks with hecate-betaCG via the lateral tail vein. The ability of hecate-betaCG to destroy xenografts of human breast cancer cells (MDA-MB-435S) in nude mice was demonstrated for the first time. We conclude that hecate-betaCG and LHRH-hecate conjugates could serve as useful drugs for the treatment of breast cancer.

Antiproliferative action of vitamin D

During the past few years, it has become apparent that vitamin D may play an important role in malignant transformation. Epidemiological studies suggest that low vitamin D serum concentration increases especially the risk of hormone-related cancers. Experimentally, vitamin D suppresses the proliferation of normal and malignant cells and induces differentiation and apoptosis. In the present review we discuss the mechanisms whereby vitamin D regulates cell proliferation and whether it could be used in prevention and treatment of hyperproliferative disorders like cancers.

Cancer chemoprevention using natural vitamin D and synthetic analogs

Substantial epidemiologic data support a role for vitamin D in cancer prevention. However, dose-limiting hypercalcemic effects have proved a major obstacle to the development of natural vitamin D as a cancer chemopreventive. Structure-activity studies have sought to disassociate the toxicities and chemopreventive activities of vitamin D, and a number of synthetic deltanoids (vitamin D analogs) have shown considerable promise in this regard. Several such compounds have chemopreventive efficacy in preclinical studies, as does natural vitamin D. Data supporting further development of agents of this class include in vitro and in vivo evidence of antiproliferative, proapoptotic, prodifferentiating and antiangiogenic activities. Ongoing studies are aimed at further defining the molecular mechanisms through which vitamin D and synthetic deltanoids affect gene expression and cellular fate. Additional efforts are focused on establishing the chemopreventive index (efficacy vs toxicity) of each synthetic deltanoid.

Functions of 1alpha,25-dihydroxyvitamin D(3) in mammary gland: from normal development to breast cancer

This review examines the role of 1alpha,25(OH)(2)D(3) (1,25D) and the vitamin D(3) receptor in growth regulation of normal and transformed mammary epithelial cells. 1,25D exerts both anti-proliferative and pro-apoptotic functions in transformed mammary cells such as MCF-7. The anti-proliferative effects of 1,25D have been linked to suppression of growth stimulatory signals and potentiation of growth inhibitory signals, which lead to changes in cell cycle regulators such as p21, p27, cyclins and Rb. The pro-apoptotic effects of 1,25D involve alterations in the relative ratios of the bcl-2 family members which regulate mitochondrial integrity. In MCF-7 human breast cancer cells, 1,25D mediated apoptosis is associated with translocation of the pro-apoptotic protein Bax to the mitochondria, generation of reactive oxygen species, dissipation of the mitochondrial membrane potential and release of cytochrome c. These mitochondrial events trigger apoptosis in a caspase-independent manner, since caspase inhibitors do not rescue 1,25D treated cells from death. The potential role of 1,25D in growth and differentiation of normal mammary epithelial cells has been examined in VDR null mice. Initial data indicates a significant decrease in ductal differentiation in VDR null mice compared to age matched wild type mice, reflected as an increased number of undifferentiated terminal end buds in the VDR null mouse. These data suggest that 1,25D promotes differentiation during early mammary gland development. In summary, our studies suggest an expanding role for the vitamin D(3) endocrine system in control of proliferation, differentiation and apoptosis of mammary epithelial cells.

The vitamin D3 analog EB 1089 enhances the antiproliferative and apoptotic effects of adriamycin in MCF-7 breast tumor cells

Exposure of MCF-7 breast tumor cells to the vitamin D3 analog, EB 1089 enhances the response to adriamycin. Clonogenic survival studies indicate that EB 1089 shifts the dose-response curve for sensitivity to adriamycin by approximately six-fold in p53 wild-type MCF-7 cells; comparative studies in MCF-7 cells with a temperature-sensitive dominant negative p53 mutation show less than a two-fold shift in adriamycin sensitivity in the presence of EB 1089. The combination of EB 1089 with adriamycin also promotes apoptotic cell death in the p53 wild-type MCF-7 cells but not in the MCF-7 cells expressing mutant p53. EB 1089 treatment blocks the increase in p21waf1/cip1 levels induced by adriamycin and interferes with induction of MAP kinase activity by ionizing radiation, effects which could be related to the capacity of EB 1089 to promote secretion of insulin-like growth factor binding protein. Taken together with our previous findings that EB 1089 enhances breast tumor cell sensitivity to ionizing radiation, there studies further support the concept that vitamin D3 analogs could have utility in combination with conventional chemotherapy and/or radiotherapy in the treatment of breast cancer.