Vitamin D: an essential adjuvant therapeutic agent in breast cancer

Abstract

Low serum levels of vitamin D have been reported as a risk factor for breast cancer. This narrative review provides an update on the impact of vitamin D on hormone receptors, notably estrogen receptor subunits, and gives insights on possible therapeutic interventions to overcome breast cancer. In addition, evidence that supports the beneficial use of vitamin D as adjuvant treatment of breast cancer is summarized. Vitamin D deficiency is significantly widespread in patients with triple-negative tumors. Several studies have observed a possible modulatory effect of vitamin D or its analogues on the expression of different hormone receptors in breast cancer and increased sensitivity to tamoxifen. Vitamin D possesses anti-inflammatory and immunomodulatory effects in patients with breast cancer, and the mechanism of action of vitamin D in patients with breast cancer is discussed. In conclusion, vitamin D appears to have a beneficial role in the prevention and management of breast cancer, however, large-scale, randomized controlled trials are needed to confirm the effects of vitamin D in breast cancer prevention or treatment.

Keywords: Breast cancer; calcitriol; cancer prevention; estrogen receptor modulation; immunoregulatory activities; pro-inflammatory cytokines.

Figure 1.

Illustration of the potential activities of calcitriol in breast cancer. Vitamin D downregulates ERα expression via inhibition of NF-κB, and increases sensitivity to tamoxifen through induction of functional ERα in ER-negative cancer cells. Its combination with tamoxifen may be effective in tamoxifen-resistant tumors. BC, breast cancer; ERRα, estrogen-related receptor α; ER, estrogen receptor; NFκB, nuclear factor- kappa B; TAM, tamoxifen; TNBC; triple negative breast cancer; TP53BP1, tumor protein P53 binding protein 1.