Abstract 2084: Autocrine regulation of laryngeal cancer tumorigenesis by 24R,25(OH)2D3

Abstract

Abstract Vitamin D3 supplementation is becoming widely accepted as a therapeutic in many common estrogen responsive cancers. Previous studies in breast cancer showed that 24R,25-dihydroxyvitamin D3 (24,25) regulates tumorigenesis via a caveolae membrane-associated signaling pathway involving phospholipase D [PLD] and palmitoylation of an unknown receptor. The goal of this study was to examine the effects of 24,25 in estrogen responsive laryngeal cancer tumorigenesis, investigate the mechanisms involved, and determine the ability of the tumor cells to produce 24,25 locally. Expression of CYP24A1 and CYP27B1 was measured in ERα66+ UM-SCC-12 (UM12) and ERα66- UM-SCC-11A (UM11A) laryngeal cancer cells. Cells were treated with 25(OH)D3, and production of the vitamin D3 metabolites 1,25(OH)2D3, 24,25(OH)2D3, and 1,24,25(OH)3D3 was measured using HPLC. The therapeutic potential of 24,25 was then assessed by treating the cells with 24,25 and measuring proliferation and apoptosis. In vivo, UM12 and UM11A cells were implanted into the cheek of NSG mice; the mice were treated with 24,25, and evaluated for survival and tumor volume. The signaling pathways involving PLD, palmitoylation, and caveolin-1 were investigated as driving mechanisms. CYP24A1 and CYP27B1 were present in ERα66+ UM12 and ERα66- UM11A cells, both of which are responsive to estrogen. When treated with 25(OH)D3, UM11A cells produced more 24,25 than UM12s, comparable to the physiologically relevant levels in blood. Both cells produced similar levels of 1,25. 24,25 increased proliferation and inhibited apoptosis in ERα66+ UM12 cells in vitro, but had the opposite effect in ERα66- UM11A cells. 24,25 increased PLD activity in UM12 cells but decreased PLD activity in UM11A cells. Inhibition of PLD activity or palmitoylation, as well as silencing expression of caveolin-1, reduced the effects of 24,25 on P53 in both cell types, indicating they played a role. Mice with UM11A tumors given 24,25 exhibited reduced tumor burden and increased survival compared to vehicle-treated controls. In contrast, mice with UM12 tumors given 24,25 had an increased tumor burden and reduced survival compared to controls. The presence of CYP24A1 and CYP27B1, local production of 24,25, and demonstration that laryngeal cancer cells respond to 24,25, indicate that 24,25 acts in an autocrine/paracrine manner. 24,25 was pro-tumorigenic in ERα66+ laryngeal cancer cells while having the opposite effect in ERα66- cells, both in vitro and in vivo, demonstrating a dependence on ERα66 expression. 24,25 acts via a mechanism involving PLD, caveolae, and palmitoylation. These data show that 24,25 regulates laryngeal cancer tumorigenesis, which is mediated by membrane associated signaling pathways that may depend on ERα66 level, and suggest a major role of 24R,25-dihydroxyvitamin D3 in laryngeal cancer. Citation Format: Cydney D. Dennis, D. Joshua Cohen, Jonathan T. Dillon, Barbara D. Boyan, Zvi Schwartz. Autocrine regulation of laryngeal cancer tumorigenesis by 24R,25(OH)2D3 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2084.