Laryngeal Cancer Cells Metabolize 25-Hydroxyvitamin D3 and Respond to 24R,25-dihydroxyvitamin D3 via a Mechanism Dependent on Estrogen Receptor Levels

Simple Summary: Vitamin D supplementation's effectiveness in reducing cancer is widely debated. The controversy may be explained by differences in 25(OH)D-3 metabolism. Previous studies showed that breast cancer cells produce vitamin D-3 metabolites locally, and their ability to regulate tumorigenesis is related to the presence of estrogen receptor alpha 66 (ER alpha 66). The present study examined this process in another estrogen-dependent cancer, laryngeal cancer. This study evaluated the effects of the active vitamin D-3 metabolite 24R,25(OH)(2)D-3 on cell growth, whether these cells can produce their own secreted vitamin D-3 metabolites, and whether this ability is related to the presence or absence of ER alpha 66. To address these questions, ER alpha-positive (UM-SCC-12) and ER alpha-negative (UM-SCC-11A) laryngeal cancer cell lines were examined for the presence of ER alpha 66; the enzymes responsible for metabolizing 25(OH)D-3 (CYP24A1 and CYP27B1); the local production of 24,25(OH)(2)D-3 and 1,25(OH)(2)D-3; and the effect of 24R,25(OH)(2)D-3 on cell growth and markers of metastasis. The results showed that laryngeal cancer cells express CYP24A1 and CYP27B1, produce 24,25(OH)(2)D-3, and respond differently to 24R,25(OH)(2)D-3, in correlation with ER alpha 66 levels. These findings suggest that tumor cells locally produce vitamin D metabolites to regulate their growth, which must be considered when recommending vitamin D supplementation. Studies have evaluated vitamin D-3's therapeutic potential in estrogen-responsive cancers, with conflicting findings. We have shown that the proliferation of breast cancer cells is regulated by 24R,25-dihydroxyvitamin D-3 (24R,25(OH)(2)D-3) depending on estrogen receptor alpha 66 (ER alpha 66) expression, suggesting that this could also be the case for estrogen-sensitive laryngeal cancer cells. Accordingly, we examined levels of ER alpha isoforms in ER alpha 66-positive UM-SCC-12 and ER alpha 66-negative UM-SCC-11A cells and their response to 24R,25(OH)(2)D-3. 24R,25(OH)(2)D-3 stimulated proliferation, increased the expression of metastatic markers, and inhibited apoptosis in UM-SCC-12 cells while having the opposite effect in UM-SCC-11A cells. To evaluate if vitamin metabolites could act via autocrine/paracrine mechanisms, we assessed the expression, protein levels, and activity of vitamin D-3 hydroxylases CYP24A1 and CYP27B1. Both cell types expressed both mRNAs; but the levels of the enzymes and their activities were differentially regulated by estrogen. ER alpha 66-negative UM-SCC-11A cells produced more 24,25(OH)(2)D-3 than UM-SCC-12 cells, but comparable levels of 1,25(OH)(2)D-3 when treated with 25(OH)D-3 These results suggest that the regulation of vitamin D-3 metabolism in laryngeal cancer cells is modulated by ER alpha 66 expression, and support a role for 24R,25(OH)(2)D-3 as an autocrine/paracrine regulator of laryngeal cancer. The local metabolism of 25(OH)D-3 should be considered when determining the potential of vitamin D-3 in laryngeal cancer.