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Vitamin D prevents ER+ breast cancer - new study

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By David Liu, PHD

Wednesday July 18, 2012 (foodconsumer.org) -- Calcitriol (1,25-dihydroxyvitamin D(3)), the hormonally active form of vitamin D, may be used to prevent and or treat a variety of cancers including breast cancer, according to a new study published July 13, 2012 in the journal Steroids.

A.V. Krishnan of Stanford University School of Medicine in Stanford, California and colleagues said in their report that calcitriol inhibits the growth of many cancerous cells including breast cancer (BCa) cells by its anticancer actions including cell cycle arrest, promotion of apoptosis and inhibition of invasion, metastasis and angiogenesis. 

The authors also said they have discovered new mechanisms that explain the inhibiting effects of calcitriol on the growth of estrogen receptor positive (ER+) breast cancer cells. 

The fact is, according to the authors, calcitriol suppresses COX-2 expression and increases expression of 15-PGDH, reducing the levels of inflammatory prostaglandins.  COx-2 refers to cyclooxygenase-2, which at high levels is linked to poor prognosis in breast cancer patients.    15-PGDH refers to 15-hydroxyprostaglandin dehydrogenase which is a tumor suppressor in breast cancer.

In addition, the researchers discovered  in their in vitro and in vivo studies that calcitriol suppresses the expression of aromatase, the enzyme that catalyzes estrogen synthesis selectively in breast cancer cells and in the adipose tissue surrounding breast cancer mass.

Anoth pathway that explains the antitumor property of vitamin D is that calcitriol down-regulates the expression of ERα which is a transcription factor involved in synthesis  of ER and thus attenuates estrogen signaling in breast cancer cells. 

Estrogen a common hormone found in humans is known to stimulate the growth of breast cancer cells.   This inhibition of estrogen synthesis and signaling induced by calcitriol and its anti-inflammatory actions in part explain why vitamin D inhibits estrogen receptor positive (ER+) breast cancer.  ER+ breast cancer means that the type of breast cancer is affected by the hormone estrogen because the breast cancer cells have ER. 

The researchers proposed that dietary vitamin D could exhibit similar anticancer activity after it is converted into calcitriol by an enzyme called 25-hydroxyvitamin D-1α-hydroxylase in breast cells.

Cell culture and in vivo data obtained in the studies led by the authors strongly suggest that calcitriol, which may be available as a prescription drug, and dietary vitamin D could potentially be used to prevent and or treat ER+ breast cancer in women.

Many epidemiological studies have associated high serum levels of vitamin D or high exposure to sun rays, which trigger synthesis of vitamin D in humans skin, with reduced risk of breast cancer.  By maintaining high levels of vitamin D in the blood, the risk for breast cancer may be reduced by up to 75 percent, according to prior research.

One in eight women are expected to develop breast cancer soon or later and the disease is diagnosed in about 210,000 American women and kills about 50,000 annually in the United States, according to the National cancer Institute.  

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