Calcitriol, the hormonally active form of vitamin D, is being evaluated in clinical trials as an anti-cancer agent. Calcitriol exerts multiple anti-proliferative, pro-apoptotic, and pro-differentiating actions on various malignant cells and retards tumor growth in animal models of cancer. Calcitriol also exhibits several anti-inflammatory effects including suppression of prostaglandin (PG) action, inhibition of p38 stress kinase signaling, and the subsequent production of pro-inflammatory cytokines and inhibition of NF-κB signaling. Calcitriol also decreases the expression of aromatase, the enzyme that catalyzes estrogen synthesis in breast cancer, both by a direct transcriptional repression and indirectly by reducing PGs, which are major stimulators of aromatase transcription. Other important effects include the suppression of tumor angiogenesis, invasion, and metastasis. These calcitriol actions provide a basis for its potential use in cancer therapy and chemoprevention. We summarize the status of trials involving calcitriol and its analogs, used alone or in combination with known anti-cancer agents.

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Mechanisms of the Anti-Cancer and Anti-Inflammatory Actions of Vitamin D

BACKGROUND Vitamin D has been hypothesized to reduce cancer mortality through its effects on incidence and/or survival. Epidemiologic studies of the association of 25-hydroxyvitamin D [25(OH)D] and the risk of cancer, however, have been largely limited to incident cancers at a few sites. METHODS A total of 16,818 participants in the Third National Health and Nutrition Examination Survey who were 17 years or older at enrollment were followed from 1988-1994 through 2000. Levels of serum 25(OH)D were measured at baseline by radioimmunoassay. Cox proportional hazards regression models were used to examine the relationship between serum 25(OH)D levels and total cancer mortality (in the entire population or according to race/ethnicity, sex, age, and retinol status) and mortality from specific cancers. Because serum was collected in the south in cooler months and the north in warmer months, we examined associations by collection season. All statistical tests were two-sided. RESULTS We identified 536 cancer deaths in 146,578 person-years. Total cancer mortality was unrelated to baseline vitamin D status in the entire population, men, women, non-Hispanic whites, non-Hispanic blacks, Mexican Americans, and in persons younger than 70 or 70 years or older. We found no interaction between vitamin D and season or vitamin D and serum retinol. Colorectal cancer mortality was inversely related to serum 25(OH)D level, with levels 80 nmol/L or higher associated with a 72% risk reduction (95% confidence interval = 32% to 89%) compared with lower than 50 nmol/L, P(trend) = .02. CONCLUSIONS Our results do not support an association between 25(OH)D and total cancer mortality, although there was an inverse relationship between 25(OH)D levels and colorectal cancer mortality.

http://www.luzimarteixeira.com.br/wp-content/uploads/2009/09/artigo6-nutricao1.pdf

Prospective Study of Serum Vitamin D and Cancer Mortality in the United States

Mutations and chromosomal translocations occur in leukemic cells that result in elevated expression or constitutive activation of various growth factor receptors and downstream kinases. The Raf/MEK/ERK, PI3K/PTEN/Akt/mTOR and Jak/STAT pathways are often activated by mutations in upstream genes. The Raf/MEK/ERK and PI3K/PTEN/Akt/mTOR pathways are regulated by upstream Ras that is frequently mutated in human cancer. Recently, it has been observed that the FLT-3 and Jak kinases and the phosphatase and tensin homologue deleted on chromosome 10 (PTEN) phosphatase are also frequently mutated or their expression is altered in certain hematopoietic neoplasms. Many of the events elicited by the Raf/MEK/ERK, PI3K/PTEN/Akt/mTOR and Jak/STAT pathways have direct effects on survival pathways. Aberrant regulation of the survival pathways can contribute to uncontrolled cell growth and lead to leukemia. In this review, we describe the Raf/MEK/ERK, PI3K/PTEN/Akt/mTOR and Jak/STAT signaling cascades and summarize recent data regarding the regulation and mutation status of these pathways and their involvement in leukemia.

Contributions of the Raf/MEK/ERK, PI3K/PTEN/Akt/mTOR and Jak/STAT pathways to leukemia

Vitamin D and cancer.

Interaction between vitamin D and the immune system has been recognized for many years, but its relevance to normal human physiology has only become evident in the past 5 years. Studies of innate immune responses to pathogens such as Mycobacterium tuberculosis have shown that pathogen-recognition receptor-mediated activation of localized vitamin D metabolism and signaling is a key event associated with infection. Vitamin D, acting in an intracrine fashion, is able to induce expression of antibacterial proteins and enhance the environment in which they function. The net effect of these actions is to support increased bacterial killing in a variety of cell types. The efficacy of such a response is highly dependent on vitamin D status; in other words, the availability of circulating 25-hydroxyvitamin D for intracrine conversion to active 1,25-dihydroxyvitamin D by the enzyme 25-hydroxyvitamin D-1α-hydroxylase. The potential importance of this mechanism as a determinant of human disease is underlined by increasing awareness of vitamin D insufficiency across the globe. This Review will explore the molecular and cellular systems associated with antibacterial responses to vitamin D in different tissues and possible consequences of such a response for the prevention and treatment of human immune disorders.

Antibacterial effects of vitamin D.

Rare mutations of the PIK3CA gene in malignancies of the hematopoietic system as well as endometrium, ovary, prostate and osteosarcomas, and discovery of a PIK3CA pseudogene.

Vitamin D3 is produced in skin and is sequentially metabolized by the liver and kidney to the biologically active form 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]. It is a seco-steroid hormone that regulates calcium homeostasis within the body. The genomic actions of 1,25(OH)2D3 are modulated through the vitamin D receptor (VDR). VDR belongs to a superfamily of nuclear receptors that transduce hormonal signals from the immediate environment and transactivate genes in response to these signals. Target genes contain hormone response elements (VDREs) in their promoters to which heterodimers of VDR and retinoid X receptors (RXR) can bind and transactivate expression of the target genes. The VDR is expressed in at least 30 different target tissues including bone, kidney, blood, breast, prostate, gut, activated B- and T- lymphocytes, monocytes and keratinocytes). Most dividing cell types, normal and malignant, can express VDR and respond to 1,25(OH)2D3. Although 1,25(OH)2D3 and its analogs (termed deltanoids) are important regulators of calcium and bone metabolism, their non-calciotropic activities that include inhibition of cell proliferation, promotion of cell differentiation and modulation of immune cell function have spurred interest in therapeutic applications in a wide variety of diseases. In this report, the anticancer and newly discovered antimicrobial actions of 1,25(OH)2D3 and deltanoids are reviewed.

Vitamin D Compounds: Activity Against Microbes and Cancer

Vitamin D compounds in leukemia.

Identification of marker genes including RUNX3 ( AML2 ) that discriminate between different myeloproliferative neoplasms and normal individuals

Quang T. Luong

Papers

Rare mutations of the PIK3CA gene in malignancies of the hematopoietic system as well as endometrium, ovary, prostate and osteosarcomas, and discovery of a PIK3CA pseudogene.

Vitamin D Compounds: Activity Against Microbes and Cancer

Vitamin D compounds in leukemia.

Identification of marker genes including RUNX3 (AML2) that discriminate between different myeloproliferative neoplasms and normal individuals.