Why vitamin D for cancer patients?

Abstract

Several epidemiological, pre-clinical and clinical studies support Vitamin D as a preventive and therapeutic cancer agent.

Background: Vitamin D and cancer: calcitriol, the biologically active form of vitamin D (1,25(OH)D), exerts its effects mainly through binding to nuclear vitamin D receptor (VDR). Calcitriol has been shown to be an anti-proliferative, pro-differentiation, pro-apoptotic agent and an inhibitor of cell migration. Animal and human in vitro studies strongly indicate that vitamin D may have benefits for many forms of cancer. Inadequate levels of circulating 25-hydroxy-vitamin D (25(OH)D) are associated with an increased risk and poor prognosis of several types of cancer. Vitamin D and melanoma: cutaneous malignant melanoma (CMM) represents a major public health issue: rates in Italy have almost doubled in the last decade and CMM is frequent among young adults. For resected stage II melanoma no standard adjuvant treatment exists and five-year overall survival is about 70%. Cultured melanoma cells can synthesize calcitriol from 25(OH)D and express the VDR. Moreover, 1,25(OH)D has anti-proliferative and pro-differentiation effects in human melanoma cells. 1,25(OH)D has been shown to induce apoptosis in human melanoma cell lines and has an inhibitory effect on the spreading of melanoma cells in vitro. Preliminary results on vitamin D: epidemiological data indicate that vitamin D deficiency is relatively common in Europe. In an Italian study, we found that 85% of the participants had insufficient levels of 25(OH)D. We have shown through a meta-analysis of randomized trials that vitamin D supplementation is associated with a significant reduction (7%) in total mortality in healthy subjects and an association between VDR and 25(OH)D and CMM progression has also been demonstrated. We have also reported significant associations between VDR polymorphisms and incidence of skin cancer. In early supplementation trials, the lack of effect on cancer incidence has been attributed to insufficient vitamin D supplementation, stressing the need to better study vitamin D bioavailability. In fact, a recent IARC report highlighted the need for new randomized trials, based on results from our meta-analyses on 25(OH)D serum levels and cancer risk. Clinical trial and biomarkers studies: in order to assess whether vitamin D supplementation could improve prognosis of CMM, an Italian multi-centre trial in stage II resected melanoma patients was planned to monitor changes in 25(OH)D. The study will address two important questions regarding the relationship between the biology of VDR and (1) vitamin D metabolism, and (2) CMM prognosis. This will involve investigating the association between VDR polymorphisms and Breslow thickness, the most important prognostic factor of CMM, and between 25(OH)D serum level, vitamin D supplementation and VDR. We will also evaluate at baseline whether VDR polymorphisms are associated with Breslow thickness and whether we obtain significant increase in 25(OH)D serum levels during the first year of supplementation. We will quantify the percentages of patients who have desirable levels of 25(OH)D and, if they don't, the mean time to reach that level. The findings from this study will be of great interest because vitamin D could have anti-cancer benefits for a wide spectrum of cancers.