Abstract 2693: The vitamin D3 metabolite, 24R,25(OH)3D3 is differentially tumorigenic in ER+ and ER- laryngeal cancer cells in vitro

Abstract

Abstract Due to the high vitamin D3 levels associated with improved prognosis (but not incidence) in post-menopausal breast cancer patients with ER+ tumors, vitamin D3 supplementation has been used as potential therapeutics. 24R,25(OH)2D3, an active metabolite of vitamin D3, is known to protect cartilage cells through a membrane-initiated, p53-mediated pathway, suggesting that 24R,25(OH)2D3 may affect cancer cells through a similar mechanism. Our lab has shown that the effect of 24R,25(OH)2D3 on breast cancer cell growth is highly dependent on the expression levels of ERα isoforms, specifically ERα66. Understanding the mechanisms by which 24R,25(OH)2D3 affects tumor growth in breast cancer will aid in determining its therapeutic potential in another estrogen responsive cancer, laryngeal cancer. The goal of this study was to examine the effects of 24R,25(OH)2D3 on proliferation, apoptosis, and epithelial to mesenchymal transition (EMT) in laryngeal cancer cell lines. To assess the effect of 24R,25(OH)2D3 on cell growth, UM-SCC-12 (ERα66+) and UM-SCC-11A (ERα66-) cell lines were cultured on 96 well plates until 80% confluence. Cells were serum starved for 24 hours pretreatment and then treated with full media containing either vehicle, or 24R,25(OH)2D3 (10-9M, 10-8M, or 10-7M) for 15 minutes, at which time the media were replaced with fresh media. After 20 hours, cells were harvested for proliferation by EDU assay. For other experiments cells were treated with either vehicle, or 24R,25(OH)2D3 (10-9M, 10-8M, or 10-7M) for 15 minutes and after 24 hours, cells were assessed for apoptosis (TUNEL, P53) and metastasis (OPG/RANKL). 12 hours after treatment, cells were harvested for PCR and examined for gene expression of apoptotic markers (BAX, BCL2) and various metastatic markers (SNAI1, ERBB2). 24R,25(OH)2D3 decreased proliferation in ERα66- cells (UM-SCC-11A) with the 10-7M dosage. It also increased apoptotic markers (TUNEL, P53, BAX/BCL2 expression). EMT and metastatic markers (ERBB2, SNAI1 expression) as well as bone metastatic markers (OPG/RANKL) were reduced. Conversely, in ERα66+ cells (UM-SCC-12) 24R,25(OH)2D3 had the opposite effect, increasing proliferation with 10-7M 24R,25(OH)2D3 treatment as well as decreasing DNA fragmentation (TUNEL). Treatment with 24R,25(OH)2D3 increased total P53 content and had no effect on EMT, BAX/BCL2 or other metastatic markers (SNAI1, ERBB2, OPG, RANKL). These data show that 24R,25(OH)2D3 is functionally active in laryngeal cancer tumor regulation. Contrary to results shown in breast cancer in which 24R,25(OH)2D3 was pro-tumorigenic in ERα66- cells, 24R,25(OH)2D3 was anti-tumorigenic in ERα66- laryngeal cancer cells. While this difference may be a result of a difference in other aspects of the two ERα66- cell lines, these results provide evidence of the therapeutic potential of 24R,25(OH)2D3 in laryngeal cancer and its ERα66 dependent effect. Citation Format: Cydney D. Dennis, David Joshua Cohen, Barbara D. Boyan, Zvi Schwartz. The vitamin D3 metabolite, 24R,25(OH)3D3 is differentially tumorigenic in ER+ and ER- laryngeal cancer cells in vitro [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2693.