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Vitamin and Drug Combination May Benefit Breast Cancer

Study suggests aromatase inhibitors and vitamin D reduce growth of breast cancers

THURSDAY, Jan. 7 (HealthDay News) -- The active form of vitamin D selectively reduces the production of aromatase, which catalyzes the production of estrogen, in breast cancers, and, when combined with aromatase inhibitors, further reduces tumor growth, according to a study in the January issue of Endocrinology.

Aruna V. Krishnan, Ph.D., and colleagues from Stanford University School of Medicine in California investigated the effect of calcitriol, the hormonally active form of vitamin D, on the expression of aromatase in various cell types and in mice bearing human breast cancers.

The researchers found that calcitriol significantly reduced aromatase expression in human breast cancer cells and adipocytes, modestly increased expression in ovarian cancer cells, and substantially increased expression in human osteosarcoma cells. Similar results were observed in immunocompromised mice bearing human breast tumors. In breast cancer cells, calcitriol also reduced the levels of prostaglandins, which stimulate aromatase expression. Combination treatment of breast cancers with calcitriol and aromatase inhibitors led to enhanced inhibition of cell growth.

"The combination of calcitriol and an aromatase inhibitor may have potential benefits for breast cancer therapy," Krishnan and colleagues conclude. "In addition to augmenting the ability of aromatase inhibitors to inhibit breast cancer growth, calcitriol acting as a selective aromatase modulator that increases aromatase expression in bone would reduce the estrogen deprivation in bone caused by the aromatase inhibitors, thus ameliorating the aromatase inhibitor-induced side effect of osteoporosis."

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