Abstract 367: The connection of vitamin D3 induced cytotoxicity with the vitamin D3 receptor

Abstract

Abstract [Purpose] This study aims to evaluate the possible antitumor effect of vitamin D. Vitamin D is a group of lipophilic compounds comprising of vitamin D2 and vitamin D3. Vitamin D3 has been shown to play an important role in humans. It has been previously reported that the onset risk of malignant melanoma and leukemia can be decreased by maintaining high vitamin D3 levels in the body. In addition, the cytotoxic effect of vitamin D on breast cancer cells has also been shown. In this study, the relationship between the cytotoxicity of vitamin D3 and vitamin D3 receptor (VDR) expression on melanoma and leukemia cells was examined. [Method] B16F10 melanoma (B16F10) and P388 leukemia (P388) cells were used in this study. Western blot analysis was performed to determine VDR expression in each cell type. To evaluate cytotoxicity, B16F10 or P388 cells were seeded at 1×105 cells/mL, and calcitriol as vitamin D3 (range 9 ng/mL-90 μg/mL) was added at once. After two days, cytotoxicity was evaluated by colorimetric analysis using Cell Counting Kit-8. Additionally, the cytotoxicity of P388 cells was determined following the combined treatment of vitamin D3 and retinoic acid. [Results and Discussion] Western blot analysis revealed that both B16F10 and P388 cell types, expressed VDR with a higher expression in P388 cells. In P388 cells, there was a significant reduction in cell viability following vitamin D3 treatment, which decreased to 10% at 90 μg/mL. In contrast, the viability of B16F10 cells following vitamin D3 treatment only slightly decreased. Interestingly, these results suggest that the cytotoxicity of vitamin D3 correlates with VDR expression. VDR reportedly forms a heterodimer with the retinoid X receptor. However, the presence of retinoic acid did not alter vitamin D3 cytotoxicity. Therefore, it was considered that cytotoxicity induced by vitamin D3 was not connected with the formation of the VDR-retinoid X receptor heterodimer. In conclusion, there was a higher expression of VDR in P388 cells compared with B16F10 cells. This higher expression correlated with a higher level of vitamin D3 cytotoxicity, suggests an antitumor effect of vitamin D3. This study proposes the possibility of using vitamin D3 as a novel treatment for leukemia and other cancers. Citation Format: Takaya Hoshi, Yuta Abe, Ikumi Sugiyama, Yasuyuki Sadzuka. The connection of vitamin D3 induced cytotoxicity with the vitamin D3 receptor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 367.