Evaluation of vitamin D analogs as therapeutic agents for prostate cancer

Is Vitamin D Deficiency Related to Increased Cancer Risk in Patients with Type 2 Diabetes Mellitus?

There is mounting evidence that type 2 diabetes mellitus (T2DM) is related with increased risk for the development of cancer. Apart from shared common risk factors typical for both diseases, diabetes driven factors including hyperinsulinemia, insulin resistance, hyperglycemia and low grade chronic inflammation are of great importance. Recently, vitamin D deficiency was reported to be associated with the pathogenesis of numerous diseases, including T2DM and cancer. However, little is known whether vitamin D deficiency may be responsible for elevated cancer risk development in T2DM patients. Therefore, the aim of the current review is to identify the molecular mechanisms by which vitamin D deficiency may contribute to cancer development in T2DM patients. Vitamin D via alleviation of insulin resistance, hyperglycemia, oxidative stress and inflammation reduces diabetes driven cancer risk factors. Moreover, vitamin D strengthens the DNA repair process, and regulates apoptosis and autophagy of cancer cells as well as signaling pathways involved in tumorigenesis i.e., tumor growth factor β (TGFβ), insulin-like growth factor (IGF) and Wnt-β-Cathenin. It should also be underlined that many types of cancer cells present alterations in vitamin D metabolism and action as a result of Vitamin D Receptor (VDR) and CYP27B1 expression dysregulation. Although, numerous studies revealed that adequate vitamin D concentration prevents or delays T2DM and cancer development, little is known how the vitamin affects cancer risk among T2DM patients. There is a pressing need for randomized clinical trials to clarify whether vitamin D deficiency may be a factor responsible for increased risk of cancer in T2DM patients, and whether the use of the vitamin by patients with diabetes and cancer may improve cancer prognosis and metabolic control of diabetes.

Development and gene expression of C57BL/6 mouse embryo palate shelves in rotary organ culture

The aim of the present study was to improve methods for the suspension culture of mouse palatal shelves by comparing the expression of platelet-derived growth factor receptor (PDGFR)-α in palatal shelves in vivo, to that in vitro. The palatal shelves of C57BL/6 mouse embryos were obtained on gestation days (GDs) 13.5, 14.5, 15.0 and 15.5 for in vivo experiments. The palatal shelves were removed and observed under a stereomicroscope to investigate palatal development. For in vitro experiments, the palatal shelves were dissected under a stereomicroscope on GD 13.5 and then subjected to rotary culture for 0, 24, 36 or 48 h. The expression of PDGFR-α at different time points was detected by immunohistochemical staining and western blot analysis. Both methods of analysis displayed PDGFR-α expression in mesenchymal and epithelial cells at GD 13.5, 14.5, 15.0 and 15.5, in vivo and in vitro. The level of PDGFR-α expression peaked on GD 14.5. The expression of PDGFR-α in palatal shelves in in vitro rotary culture was consistent with that in vivo. Therefore, the novel technique of palatal rotary organ culture presented in the current study could provide a good model for studying the mechanism of pathological palatal fusion in vitro. Additionally, the present study further confirmed that PDGFR-α gene expression was associated with the development of palatal shelves.

Exploring vitamin D metabolism and function in cancer

Vitamin D, traditionally known as an essential nutrient, is a precursor of a potent steroid hormone that regulates a broad spectrum of physiological processes. In addition to its classical roles in bone metabolism, epidemiological, preclinical, and cellular research during the last decades, it revealed that vitamin D may play a key role in the prevention and treatment of many extra-skeletal diseases such as cancer. Vitamin D, as a prohormone, undergoes two-step metabolism in liver and kidney to produce a biologically active metabolite, calcitriol, which binds to the vitamin D receptor (VDR) for the regulation of expression of diverse genes. In addition, recent studies have revealed that vitamin D can also be metabolized and activated through a CYP11A1-driven non-canonical metabolic pathway. Numerous anticancer properties of vitamin D have been proposed, with diverse effects on cancer development and progression. However, accumulating data suggest that the metabolism and functions of vitamin D are dysregulated in many types of cancer, conferring resistance to the antitumorigenic effects of vitamin D and thereby contributing to the development and progression of cancer. Thus, understanding dysregulated vitamin D metabolism and function in cancer will be critical for the development of promising new strategies for successful vitamin D-based cancer therapy.

Resurgence of vitamin D: Old wine in new bottle

There are early references of it in ancient text and physicians have discussed its importance and features of its deficiency in the past. Vitamin D has again regained interest with recent dramatic rise in the incidence of deficiency in the developing as well as developing world. In this review article, we discuss the biochemical and role of vitamin D in the skeletal system. We also discuss the recommended dietary requirements and features of skeletal deficiency. Extra-skeletal roles of vitamin D deficiency have been a matter of debate lately and it has also been discussed in detail in this article. In conclusion, it would not be wrong to label vitamin D as one of the most important vitamin involved in the metabolism of the musculoskeletal system and any clinician, especially the orthopaedician, should be well versed with its overall mechanism and roles in the human body.

Investigation of Bone Health Subsequent to Vitamin D Supplementation in Children Following Burn Injury

BACKGROUND

The effect of supplemental vitamin D on fracture occurrence following burn injuries is unclear. The objective of this study was to evaluate postintervention incidence of fractures in children during the rehabilitative phase postburn (PB) following participation in a randomized clinical trial of vitamin D supplementation.

MATERIALS AND METHODS

Follow-up for fracture evaluation was obtained in 39 of 50 patients randomized to daily enteral vitamin D2, D3, or placebo throughout the acute burn course. Serum 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, D2, D3, calcitonin, and bone alkaline phosphatase (BAP) measurements were obtained PB day 7, midpoint, discharge, and 1-year PB. Urinary calcium was obtained PB day 7 and midpoint. Dual-energy x-ray absorptiometry (DXA) was performed at discharge and 1-year PB.

RESULTS

Fractures were reported in 6 of 39 respondents. Four fractures occurred in the placebo group, 2 in the D2 group, and none in the D3 group. Serum vitamin D, calcitonin, BAP, and urinary calcium were similar between fracture groups. The group with fracture morbidity had larger burn size (83.8% ± 4.9% vs 53.0% ± 2.9%, P < .0001), greater full-thickness burn (69.7% ± 9.4% vs 39.4% ± 4.1%, P = .02), and increased incidence of inhalation injury (33% vs 6%, P = .04). Decreased bone mineral density z score was noted at discharge in the placebo fracture compared with no-fracture group (P < .05).

CONCLUSION

This preliminary report suggests there may be benefit of vitamin D3 in reducing postdischarge fracture risk. Results reaffirm the importance of monitoring bone health in pediatric patients postburn.

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.

Current progress in using vitamin D and its analogs for cancer prevention and treatment

Vitamin D has long been known for its physiological role in mineral homeostasis through its actions on the intestines, kidneys, parathyroid glands and bone. However, recent observations of antiproliferative, prodifferentiating and antiangiogenic effects elicited by the bioactive form of vitamin D (1,25[OH](2)D(3)) in a broad range of cancers is less well understood. Here, we review the increasing epidemiological and experimental evidence that supports the development of 1,25(OH)(2)D(3) and vitamin D analogs as preventative and therapeutic anticancer agents. Furthermore, this review summarizes the preclinical and clinical studies of vitamin D and its analogs over the past decade, indicating the current problems of dose-limiting toxicity from hypercalcemia and large interpatient variability in pharmacokinetics. A better understanding of how genetic variants influence vitamin D status should not only improve cancer risk predictions, but also promote the development of vitamin D analogs with more specific actions to improve therapeutic outcomes.

Vitamin D and cancer: a review of molecular mechanisms

The population-based association between low vitamin D status and increased cancer risk can be inconsistent, but it is now generally accepted. These relationships link low serum 25OHD (25-hydroxyvitamin D) levels to cancer, whereas cell-based studies show that the metabolite 1,25(OH)2D (1,25-dihydroxyvitamin D) is a biologically active metabolite that works through vitamin D receptor to regulate gene transcription. In the present review we discuss the literature relevant to the molecular events that may account for the beneficial impact of vitamin D on cancer prevention or treatment. These data show that although vitamin D-induced growth arrest and apoptosis of tumour cells or their non-neoplastic progenitors are plausible mechanisms, other chemoprotective mechanisms are also worthy of consideration. These alternative mechanisms include enhancing DNA repair, antioxidant protection and immunomodulation. In addition, other cell targets, such as the stromal cells, endothelial cells and cells of the immune system, may be regulated by 1,25(OH)2D and contribute to vitamin D-mediated cancer prevention.

Novel vitamin d analogs for prostate cancer therapy

Prostate cells contain specific receptors for 1α,25-dihydroxyvitamin D [1α,25(OH)₂D] or calcitriol, the active form of vitamin D. 1α,25(OH)₂D is known to inhibit the proliferation and invasiveness of prostate cancer cells. These findings support the use of 1α,25(OH)₂D for prostate cancer therapy. However, 1α,25(OH)₂D can cause hypercalcemia, analogs of 1α,25(OH)₂D that are less calcemic but exhibit potent antiproliferative activity would be attractive as therapeutic agents. To accomplish these goals, different strategies, based on metabolism, molecular mechanism of actions, and structural modeling, have been taken to modify the structure of vitamin D molecule with the aims to improve the efficacy and decrease the toxicity of vitamin D to treat different diseases. During the past four decades, over 3,000 analogs have been synthesized. In this paper, we discuss the development and the biological analysis of a unique class of vitamin D analogs with a substitution at the carbon 2 of 19-nor-1α,25(OH)₂D₃ molecule for potential application to the prevention and treatment of prostate cancer as well as other cancers.

A new steroidal 5,7-diene derivative, 3beta-hydroxyandrosta-5,7-diene-17beta-carboxylic acid, shows potent anti-proliferative activity

The new steroidal 5,7-diene, 3beta-hydroxyandrosta-5,7-diene-17beta-carboxylic acid (17-COOH-7DA), was synthesized from 21-acetoxypregnenolone, with the oxidative cleavage of the side chain being dependent on the presence of oxygen. In human epidermal (HaCaT) keratinocytes, 17-COOH-7DA inhibited proliferation in a dose-dependent manner, starting at a dose as low as 10(-11) M. This inhibition was accompanied by decreased expression of epidermal growth factor receptor, bcl2 and cyclin E2 mRNAs and by increased expression of involucrin mRNA. Inhibition of proliferation was associated with slowing of the cell cycle in G1/G0 phases but not with cell death. 17-COOH-7DA was significantly more potent than pregnenolone, 17-COOH-pregnenolone, 17-COOCH(3)-7DA and calcitriol. 17-COOH-7DA also inhibited proliferation of normal human epidermal melanocytes and human and hamster melanoma lines, however, with lower potency than for keratinocytes. In normal human dermal fibroblasts 17-COOH-7DA stimulated proliferation in serum-free media but inhibited it in the presence of 5% serum. 17-COOH-7DA inhibited cell colony formation of human and hamster melanoma cells, and induced monocyte-like differentiation of human HL60 leukemia cells. Thus, the new steroidal 5,7-diene, 17-COOH-7DA, can serve as an inhibitor of proliferation of normal keratinocytes and normal and malignant melanocytes, as a condition-dependent regulator of fibroblast proliferation and a stimulator of leukemia cell differentiation.

Nutraceuticals and prostate cancer prevention: a current review

Nutraceuticals are 'natural' substances isolated or purified from food substances and used in a medicinal fashion. Several naturally derived food substances have been studied in prostate cancer in an attempt to identify natural preventative therapies for this disease. Vitamin E, selenium, vitamin D, green tea, soy, and lycopene have all been examined in human studies. Other potential nutraceuticals that lack human data, most notably pomegranate, might also have a preventative role in this disease. Unfortunately, most of the literature involving nutraceuticals in prostate cancer is epidemiological and retrospective. The paucity of randomized control trial evidence for the majority of these substances creates difficulty in making clinical recommendations particularly when most of the compounds have no evidence of toxicity and occur naturally. Despite these shortcomings, this area of prostate cancer prevention is still under intense investigation. We believe many of these 'natural' compounds have therapeutic potential and anticipate future studies will consist of well-designed clinical trials assessing combinations of compounds concurrently.

EB1089 induces Skp2-dependent p27 accumulation, leading to cell growth inhibition and cell cycle G1 phase arrest in human hepatoma cells

EB1089 exhibits a high level of antiproliferative activity against various tumors. However, it is not known whether the mechanism of EB1089 induced the growth inhibition in human hepatic-carcinoma. Here we found that EB1089 significantly reduced cell growth in human hepatoma cells (Hep-G2) and blocked Hep-G2 cell-associated tumor formation in nude mice. The growth inhibition was linked to cell cycle G1 phase arrest by the accumulation of p27 and a reduction of Skp2. Knockdown of Skp2 reversed the p27 induction and G1 arrest. Taken together, our data indicate that EB1089 inhibitory activity is associated with alteration of cell cycle checkpoints through Skp2-dependent p27 induction in Hep-G2 cells.

Prostate cancer, serum parathyroid hormone, and the progression of skeletal metastases

Bony metastases from prostate cancer are a significant cause of morbidity and mortality. These metastases are predominantly blastic (bone-forming) and commonly cause increased serum levels of parathyroid hormone (PTH) as calcium ions are transferred from serum into blastic bone. The epidemiologic and clinical significance of secondary hyperparathyroidism in advanced prostate cancer have not been widely appreciated. Prostate cancer bony metastases show increased expression of the PTH receptor (PTH-IR) and PTH promotes the growth and invasiveness of prostate cancer cells in bone. Thus, blastic metastases appear to induce a "vicious cycle" in which PTH resorbs normal bone to support the growth of blastic bone. Recognition of the potential role of PTH in the progression of skeletal metastases suggests novel opportunities for prostate cancer secondary prevention. In particular, we propose that suppressing serum PTH in advanced prostate cancer may reduce morbidity by decreasing fractures and pain caused by bone resorption and may reduce mortality by retarding the progression of metastatic disease.

Induction of differentiation of human leukemia cells by combinations of COX inhibitors and 1,25-dihydroxyvitamin D3 involves Raf1 but not Erk 1/2 signaling

Differentiation therapy of cancer is being explored as a potential modality for treatment of myeloid leukemia, and derivatives of vitamin D are gaining prominence as agents for this form of therapy. Cyclooxygenase (COX) inhibitors have been reported to enhance 1,25-dihydroxyvitamin D(3) (1,25D)-induced monocytic differentiation of promyeloblastic HL60 cells, but the mechanisms of this effect are not fully elucidated, and whether this potentiation can occur in other types of myeloid leukemia is not known. We found that combination treatment with 1,25D and non-specific COX inhibitors acetyl salicylic acid (ASA) or indomethacin can robustly potentiate differentiation of other types of human leukemia cells, i.e., U937, THP-1, and that ASA +/- 1,25D is effective in primary AML cultures. Increased cell differentiation is paralleled by arrest of the cells in the G(1) phase of the cell cycle, and by increased phosphorylation of Raf1 and p90RSK1 proteins. However, there is no evidence that this increase in phosphorylation of Raf1 is transmitted through the ERK module of the MAPK signaling cascade. Transfection of small interfering (si) RNA to Raf1 decreased differentiation of U937 cells induced by a combination of ASA or indomethacin with 1,25D. However, phosphorylation levels of ERK1/2, though not of p90RSK, were increased when P-Raf1 levels were decreased by the siRNA, suggesting that in this system the ERK module does not function in the conventional manner. Identification of the strong antiproliferative activity of ASA/1,25D combinations associated with monocytic differentiation has implications for cancer chemoprevention in individuals who have a predisposition to myeloid leukemia.

Overexpression of vitamin D receptor indicates a good prognosis for cholangiocarcinoma: implications for therapeutics

BACKGROUND

Up-regulation of vitamin D receptor (VDR) expression has been shown in several tumors and is thought to represent an important endogenous response to tumor progression. The authors aimed to verify the expression of VDR and its clinical significance in histologically proven cholangiocarcinoma (CCA).

METHODS

The antiproliferative activity of vitamin D3 on CCA cell lines was explored. The immunohistochemistry of 111 paraffin-embedded CCA tissues showed that VDR expression gradually increased during CCA development. Normal bile duct epithelium rarely expresses VDR, whereas more than 74% of CCA tissues showed positive VDR staining, of which 40% were high. Approximately 80%-90%of CCA patients with papillary and well differentiated adenocarcinomas had positive VDR expression in tumor tissues, whereas 39% positive VDR expression was found in those with poorly differentiated CCAs (P < .001).

RESULTS

Expression of VDR was shown to be compatible with an overall favorable prognosis for CCA. Treatment with 1,25(OH)(2)D(3), an active metabolite of vitamin D3, in the CCA cell lines with high expression of VDR significantly reduced cell proliferation in a dose-dependent manner. The effect was not demonstrated in the CCA cell lines that had lower VDR expression.

CONCLUSIONS

These data indicated an active role for VDR in mediating the antiproliferative effects of 1,25(OH)(2)D(3) in CCA cell lines. VDR expression may constitute an important prerequisite for using vitamin D and/or its analogs in the treatment of CCA. Investigation of a mechanism by which VDR and its ligand mediate these processes is needed to provide the basis for the potential use of this hormone and its derivatives in the prevention and treatment of CCA.

A prospective study of dietary calcium, dairy products and prostate cancer risk (Finland)

High dietary intakes of calcium and dairy products have been hypothesized to enhance prostate cancer risk, but available prospective data regarding these associations are inconsistent. We examined dietary intakes of calcium and dairy products in relation to risk of prostate cancer in the Alpha-Tocopherol, Beta-Carotene (ATBC) Cancer Prevention Study, a cohort of 29,133 male smokers aged 50-69 years at study entry. Dietary intake was assessed at baseline using a validated 276-item food use questionnaire. Cox proportional hazards regression was used to adjust for known or suspected risk factors for prostate cancer. During 17 years of follow-up, we ascertained 1,267 incident cases of prostate cancer. High versus low intake of dietary calcium was associated with a marked increase in prostate cancer risk. The multivariate relative risk (RR) of prostate cancer for > or =2,000 mg/day compared to <1,000 mg/day of calcium intake was 1.63 (95% confidence interval (CI), 1.27-2.10; p trend < 0.0001). Total dairy intake was also positively associated with risk of prostate cancer. The multivariate RR of prostate cancer comparing extreme quintiles of intake was 1.26 (95% CI, 1.04-1.51; p trend = 0.03). However, no association with total dairy intake remained after we adjusted for calcium (p trend = 0.17). Findings were similar by stage and grade of prostate cancer. The results from this large prospective study suggest that intake of calcium or some related component contained in dairy foods is associated with increased prostate cancer risk.

High prevalence of vitamin D inadequacy and implications for health

During the past decade, major advances have been made in vitamin D research that transcend the simple concept that vitamin D is Important for the prevention of rickets in children and has little physiologic relevance for adults. Inadequate vitamin D, in addition to causing rickets, prevents children from attaining their genetically programmed peak bone mass, contributes to and exacerbates osteoporosis in adults, and causes the often painful bone disease osteomalacia. Adequate vitamin D is also important for proper muscle functioning, and controversial evidence suggests it may help prevent type 1 diabetes mellitus, hypertension, and many common cancers. Vitamin D inadequacy has been reported in approximately 36% of otherwise healthy young adults and up to 57% of general medicine inpatients in the United States and in even higher percentages in Europe. Recent epidemiological data document the high prevalence of vitamin D inadequacy among elderly patients and especially among patients with osteoporosis. Factors such as low sunlight exposure, age-related decreases in cutaneous synthesis, and diets low in vitamin D contribute to the high prevalence of vitamin D inadequacy. Vitamin D production from cutaneous synthesis or intake from the few vitamin D-rich or enriched foods typically occurs only intermittently. Supplemental doses of vitamin D and sensible sun exposure could prevent deficiency in most of the general population. The purposes of this article are to examine the prevalence of vitamin D inadequacy and to review the potential implications for skeletal and extraskeletal health.

Phase I/II study of 19-nor-1alpha-25-dihydroxyvitamin D2 (paricalcitol) in advanced, androgen-insensitive prostate cancer

PURPOSE

We assessed the safety and efficacy of the vitamin D analogue, 19-nor-1alpha-25-dihydroxyvitamin D2 (paricalcitol), in patients with androgen-independent prostate cancer.

EXPERIMENTAL DESIGN

Patients received paricalcitol i.v. three times per week on an escalating dose of 5 to 25 microg (3-15 microg/m2). The primary end point was prostate-specific antigen (PSA) response. Secondary end points were characterization of toxicity in this population, changes in serum parathyroid hormone (PTH), and survival.

RESULTS

A total of 18 patients were enrolled. No patient showed a sustained 50% drop in serum PSA, despite several large declines in PSA (e.g., 1,300 ng/mL). Paricalcitol was well tolerated. One instance of significant hypercalcemia, a serum calcium of 14.3 mg/dL, was observed at the highest dose (25 microg). At entry into the study, seven (41%) of the patients had elevated serum levels of PTH, which were significantly reduced by paricalcitol. Higher levels of serum PTH at study entry were significantly and negatively associated with survival (P<0.01).

CONCLUSION

No objective responses were seen in the primary end point. However, elevated serum levels of PTH, a common feature of advanced prostate cancer, were reduced by paricalcitol. Because elevated PTH is associated with increased cardiovascular and skeletal morbidity, including an increased risk for pathologic fracture, further evaluation of paricalcitol in the reduction of skeletal morbidity in advanced prostate cancer is warranted.

Vitamin D and the epidemiology of prostate cancer

Mortality rates from prostate cancer are significantly higher among African Americans than Caucasian Americans and are inversely related to the availability of ultraviolet (UV) radiation. These findings support the hypothesis, originally proposed in 1990, that prostate cancer may be caused by vitamin D deficiency. In 1992, specific receptors for 1,25-dihydroxyvitamin D [1,25(OH)2D] were demonstrated in human prostate cells. We and others have shown that 1,25(OH)2D exerts prodifferentiating, antiproliferative, and antimetastatic effects on these cells. In 1998 we demonstrated that normal prostate cells express 1alpha-hydroxylase and synthesize their own 1,25(OH)2D. Thus, 1,25(OH)2D is an autocrine hormone in the prostate. The consensus emerging from analytic epidemiologic studies is that low levels of UV radiation/vitamin D are indeed associated with an increased risk of prostate cancer in individual men. The evolution of our understanding of the role of vitamin D in the epidemiology of prostate cancer parallels our understanding of the role of vitamin D in the epidemiology of rickets. In both diseases, ecologic observations about UV radiation preceded experimental observations and were subsequently validated by them.

Hypocalcemia and Parathyroid Function in Metastatic Prostate Cancer

OBJECTIVE

To report the occurrence of hypocalcemia in a patient with metastatic prostate cancer, discuss its pathogenesis, and review the related medical literature.

METHODS

An 82-year-old man with a known history of prostate cancer was found to have a serum calcium level of 5.4 mg/dL during an admission to the hospital for small bowel obstruction. A thorough review of his medical history revealed a temporal relationship between the diagnosis of malignant disease and progressive hypocalcemia. A complete evaluation was performed, including laboratory and imaging studies, to ascertain the cause of the hypocalcemia.

RESULTS

The patient had no history of hypocalcemia before the diagnosis of, and initiation of antiandrogen therapy for, advanced prostate cancer. Serum magnesium and phosphorus levels were within normal limits. The serum calcium level responded to therapy in the hospital but remained between 5.8 and 7.1 mg/dL. The parathyroid hormone level was normal, and the 25-hydroxyvitamin D value was low. A 24-hour urine collection showed substantially reduced calcium excretion, and a whole-body bone scan revealed widespread metastatic deposits. These findings were compatible with hypocalcemia related to prostate cancer and bone metastatic lesions.

CONCLUSION

This case serves as a reminder that hypocalcemia can be a manifestation of prostate cancer metastatic to bone. In contrast to the occurrence of secondary hyperparathyroidism in this setting, however, this patient had normal levels of parathyroid hormone. Review of similar previous reports and the causes and implications of a possible functional hypoparathyroid state are discussed.

Growth Suppression of Ovarian Cancer Xenografts in Nude Mice by Vitamin D Analogue EB1089

Purpose: The poor response of advanced epithelial ovarian cancer to current treatments necessitates the development of alternative therapeutic strategies. Inhibition of cancer growth by 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] compounds represents an innovative approach for cancer therapy. The current study evaluated the therapeutic potential of a synthetic 1,25(OH)2D3 analogue EB1089 in the treatment of ovarian cancer.

Experimental Design: The response of human ovarian cancer cells to 1,25(OH)2D3 and EB1089 were first compared in cell growth, gene transcription, and apoptotic assays. Then, nude mice bearing OVCAR3 tumor xenografts were treated with EB1089 at different dosages, and tumor volumes were monitored. The effect of EB1089 and 1,25(OH)2D3 on the level of serum calcium was also examined. After the treatment, tumors were excised and processed for histologic examination, Ki-67 staining, and tissue terminal deoxynucleotide transferase–mediated dUTP nick end labeling (TUNEL) assays to evaluate the morphologic, proliferative, and apoptotic changes induced by EB1089, respectively.

Results: The study shows that EB1089 suppresses the in vitro growth of ovarian cancer cells and transcriptionally activates the GADD45 reporter gene more effectively than 1,25(OH)2D3. Clinically more importantly, EB1089 suppresses the growth of OVCAR3 tumor xenografts in nude mice without inducing hypercalcemia. Ki-67 staining and tissue TUNEL assays showed that both inhibition of cell proliferation and induction of apoptosis contribute to the EB1089-induced tumor suppression in vivo.

Conclusions: This study is the first demonstration that ovarian cancer responds positively in vivo to treatment with a 1,25(OH)2D3 compound and thus supports continued development of 1,25(OH)2D3 analogues for possible use as an alternative or complementary therapy for human ovarian 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.

Why the optimal requirement for Vitamin D3 is probably much higher than what is officially recommended for adults

The physiologic range for circulating 25-hydroxyvitamin D3 [25(OH)D; the measure of Vitamin D nutrient status] concentration in humans and other primates extends to beyond 200 nmol/L (>80 ng/mL). This biologic "normal" value is greater than current population norms for 25(OH)D. Concentrations of 25(OH)D that correlate with desirable effects extend to at least 70 nmol/L, with no obvious threshold. Randomized clinical trials using 20 mcg (800 IU) per day of Vitamin D show that this suppresses parathyroid hormone, preserves bone mineral density, prevents fractures, lowers blood pressure and improves balance. Calcium absorption from diet correlates with 25(OH)D in the normal range. Health effects of Vitamin D beyond osteoporosis are mostly supported by the circumstantial evidence of epidemiologic studies and laboratory research. These include prevention of cancer and the autoimmune diseases, insulin-dependent diabetes and multiple sclerosis. One mcg per day of Vitamin D(3) (cholecalciferol) increases circulating 25(OH)D by about 1 nmol/L (0.4 ng/mL). A recommended dietary allowance (RDA) is the long-term daily intake level that meets the total requirements for the nutrient by nearly all healthy individuals (it would presume no sunshine). If 70 nmol/L is regarded as a minimum desirable target 25(OH)D concentration, then current recommendations of 15 mcg per day do not meet the criterion of an RDA.

Sunshine is good medicine. The health benefits of ultraviolet-B induced vitamin D production

Most public health statements regarding exposure to solar ultraviolet radiation (UVR) recommend avoiding it, especially at midday, and using sunscreen. Excess UVR is a primary risk factor for skin cancers, premature photoageing and the development of cataracts. In addition, some people are especially sensitive to UVR, sometimes due to concomitant illness or drug therapy. However, if applied uncritically, these guidelines may actually cause more harm than good. Humans derive most of their serum 25-hydroxycholecalciferol (25(OH)D3) from solar UVB radiation (280-315 nm). Serum 25(OH)D3 metabolite levels are often inadequate for optimal health in many populations, especially those with darker skin pigmentation, those living at high latitudes, those living largely indoors and in urban areas, and during winter in all but the sunniest climates. In the absence of adequate solar UVB exposure or artificial UVB, vitamin D can be obtained from dietary sources or supplements. There is compelling evidence that low vitamin D levels lead to increased risk of developing rickets, osteoporosis and osteomaloma, 16 cancers (including cancers of breast, ovary, prostate and non-Hodgkin's lymphoma), and other chronic diseases such as psoriasis, diabetes mellitus, hypertension, heart disease, myopathy, multiple sclerosis, schizophrenia, hyperparathyroidism and susceptibility to tuberculosis. The health benefits of UVB seem to outweigh the adverse effects. The risks can be minimized by avoiding sunburn, excess UVR exposure and by attention to dietary factors, such as antioxidants and limiting energy and fat consumption. It is anticipated that increasing attention will be paid to the benefits of UVB radiation and vitamin D and that health guidelines will be revised in the near future.