Vitamin D and prostate cancer risk--a less sunny outlook?

The role of mass spectrometry in the analysis of vitamin D compounds

This review highlights the superseding role of mass spectrometry in the structural characterization and quantitation of vitamin D compounds in comparison to other analytical methods (e.g., UV, bioassays) that lack the sensitivity and specificity of mass spectrometry. After a short introduction to the biochemistry of vitamin D compounds, an overview of the current techniques to characterize and quantitate vitamin D compounds is given with emphasis on the contribution of mass spectrometry.

Chemoprevention of prostate cancer: Natural compounds, antiandrogens, and antioxidants - In vivo evidence

Prostate cancer is the leading non-skin malignancy detected in US males and the second cause of death due to male cancer, in the US. Interventions with drugs or diet supplements that slow down the growth and progression of prostate cancer are potentially very effective in reducing the burden of prostate cancer, particularly if these treatments also prevent the de novo development of new prostatic malignancies. Challenges to identify efficacious agents and develop them for chemopreventive application in men at risk for prostate cancer have included uncertainty about which preclinical models have the ability to predict efficacy in men and lack of consensus about which early phase clinical trial designs are the most appropriate and cost-effective to test promising agents. Efficacy studies in animal models have identified several agents with potential chemopreventive activity against prostate cancer, but few of these findings have been translated into clinical trials. This article identifies some of the major issues associated with prostate cancer chemoprevention research and summarizes the most significant current results from animal efficacy studies and human clinical prevention trials. This summary focuses on: (1) Naturally occurring agents and compounds derived from such agents, including green tea and its constituents, silibinin and milk thistle, and genistein and soy, (2) chemoprevention drugs including agents interfering with androgen action, and (3) antioxidants such as selenium, vitamin E, and lycopene. The general lack of activity of antioxidants is discussed, followed by considerations about translation of preclinical chemoprevention efficacy data, focusing on dose, form, bioavailability, and timing of administration of the agent, as well as discussion of study design of clinical trials and the predictive ability of preclinical models.

Vitamin d, sunlight and prostate cancer risk

Prostate cancer is the second common cancer in men worldwide. The prevention of prostate cancer remains a challenge to researchers and clinicians. Here, we review the relationship of vitamin D and sunlight to prostate cancer risk. Ultraviolet radiation of the sunlight is the main stimulator for vitamin D production in humans. Vitamin D's antiprostate cancer activities may be involved in the actions through the pathways mediated by vitamin D metabolites, vitamin D metabolizing enzymes, vitamin D receptor (VDR), and VDR-regulated genes. Although laboratory studies including the use of animal models have shown that vitamin D has antiprostate cancer properties, whether it can effectively prevent the development and/or progression of prostate cancer in humans remains to be inconclusive and an intensively studied subject. This review will provide up-to-date information regarding the recent outcomes of laboratory and epidemiology studies on the effects of vitamin D on prostate cancer prevention.

Prevalence of serum vitamin D deficiency and insufficiency in cancer: Review of the epidemiological literature

Vitamin D deficiency has been found to be associated with a variety of cancers, including prostate, multiple myeloma, colorectal and breast cancer. Several studies have shown vitamin D levels to have an inverse relation with cancer mortality, while others have considered it a potential risk factor. Vitamin D is believed to influence cancer prevalence, risk and survival; hence the need to assess vitamin D levels in cancer. Although numerous studies have been conducted to demonstrate vitamin D deficiency as a risk factor for cancer, relatively few have studied its prevalence. Moreover, studies estimating prevalence differ from each other, with respect to study population, sample size, study design, definition of vitamin D deficiency used and method of vitamin D assessment (with most studies limited to one particular type of cancer with relatively small sample sizes). Therefore, we qualitatively reviewed the epidemiological evidence in the oncology literature on the prevalence of vitamin D deficiency and insufficiency as measured by serum vitamin D concentrations.

Impact of oral vitamin D supplementation on serum 25-hydroxyvitamin D levels in oncology

BACKGROUND

Serum 25-hydroxyvitamin D [25(OH)D] is the major circulating form of vitamin D and a standard indicator of vitamin D status. Emerging evidence in the literature suggests a high prevalence of suboptimal vitamin D (as defined by serum 25(OH)D levels of <32 ng/ml) as well as an association between lower serum levels and higher mortality in cancer. We investigated the effect of oral vitamin D supplementation as a means for restoring suboptimal levels to optimal levels in cancer.

METHODS

This is a retrospective observational study of 2198 cancer patients who had a baseline test prior to initiation of cancer therapy at our hospital to evaluate serum 25(OH)D levels between Jan 08 and Dec 09 as part of their initial nutritional evaluation. Patients with baseline levels of < = 32 ng/ml (n = 1651) were considered to have suboptimal serum 25(OH)D levels and were supplemented with 8000 IU of Vitamin D3 (four 2000 IU D3 capsules) daily as part of their nutritional care plan. The patients were retested at their first follow-up visit. Of 1651 patients, 799 were available for follow up assessment. The mean serum 25(OH)D levels were compared in these 799 patients across the 2 time points (baseline and first follow-up) using paired sample t-test. We also investigated the factors associated with response to vitamin D supplementation.

RESULTS

Of 2198 patients, 814 were males and 1384 females. 1051 were newly diagnosed and treated at our hospital while 1147 were diagnosed and treated elsewhere. The mean age at presentation was 55.4 years. The most common cancer types were breast (500, 22.7%), lung (328, 14.9%), pancreas (214, 9.7%), colorectal (204, 9.3%) and prostate (185, 8.4%). The mean time duration between baseline and first follow-up assessment was 14.7 weeks (median 10.9 weeks and range 4 weeks to 97.1 weeks). The mean serum 25(OH)D levels were 19.1 ng/ml (SD = 7.5) and 36.2 ng/ml (SD = 17.1) at baseline and first follow-up respectively; p < 0.001. Patients with prostate and lung cancer had the highest percentage of responders (70% and 69.2% respectively) while those with colorectal and pancreas had the lowest (46.7% each). Similarly, patients with serum levels 20-32 ng/ml at baseline were most likely to attain levels > 32 ng/ml compared to patients with baseline levels < 20 ng/ml.

CONCLUSIONS

The response to supplementation from suboptimal to optimal levels was greatest in patients with prostate and lung cancer as well as those with baseline levels between 20-32 ng/ml. Characteristics of non-responders as well as those who take longer to respond to supplementation need to be further studied and defined. Additionally, the impact of improved serum 25(OH)D levels on patient survival and quality of life needs to be investigated.

Vitamins and prostate cancer risk

Prostate cancer (PC) is the second most common cancer in men worldwide. Its prevention and treatment remain a challenge to clinicians. Here we review the relationship of vitamins to PC risk. Many vitamins and related chemicals, including vitamin A, retinoids, several B vitamins, vitamin C, vitamin D and vitamin E have shown their anti-cancer activities as anti-oxidants, activators of transcription factors or factors influencing epigenetic events. Although laboratory tests including the use of animal models showed these vitamins may have anti-PC properties, whether they can effectively prevent the development and/or progression of PC in humans remains to be intensively studied subjects. This review will provide up-to-date information regarding the recent outcomes of laboratory, epidemiology and/or clinical trials on the effects of vitamins on PC prevention and/or treatment.

Vitamin D and prostate cancer risk: a review of the epidemiological literature

Prostate cancer is the most commonly diagnosed cancer in the United States. Prostate cells contain vitamin D receptors as well as enzymes necessary for vitamin D metabolism. Vitamin D metabolites have an antiproliferative and a pro-differentiating effect on prostate cancer cell lines in vitro and in vivo. As a result, there has been an emerging interest in the potential role of vitamin D in the etiology of prostate cancer. This review summarizes all available epidemiological literature on the association between dietary vitamin D, circulating levels of vitamin D and sunlight exposure in relation to prostate cancer risk. To place these studies in context, we also provide some background information on vitamin D, such as its dietary sources, metabolism, optimal levels, hypovitaminosis and relationship with the prostate.

Vitamin D, vitamin D analogs (deltanoids) and prostate cancer

'Vitamin D' is a generic term for a family of secosteroids, members of which bind to the vitamin D receptor. Calcitriol, the active form of vitamin D, has antiproliferative effects on many tumor cells. However, clinical use of calcitriol in cancer prevention or therapy is limited because it induces hypercalcemia at the necessary supraphysiological doses. The anti-tumor effects of vitamin D analogs (deltanoids) have been researched extensively; more than 3000 deltanoids have now been described. Prostate cancer is more common in northern geographic regions; mortality decreases with exposure to sunlight. As UV light is necessary for vitamin D synthesis in the skin, it has long been dogma that vitamin D is involved. This review concerns deltanoids that have been assessed for use in treating or preventing prostate cancer.