Abstract 62: Vitamin D3 induces 15-Hydroxyprostaglandin Dehydrogenase to suppress pancreatic cancer cell proliferation
Authors: Hung Pham, Monica Chen, Hiroki Takahashi, Howard A. Reber, Joe Hines, Guido Eibl
Journal: Cancer Research (2012)

Abstract BACKGROUND: Excess prostaglandin E2 (PGE2) mediates growth and survival of several cancers, including prostate and pancreatic cancers (PaCa). 15-Hydroxyprostaglandin dehydrogenase (PGDH) catalyzes PGE2 to an inactive 15-keto metabolite. We have previously shown that PGDH is down-regulated in human PaCa, contributing to accumulated levels of PGE2 that can subsequently feed back to suppress further PGDH expression. In contrast, PGDH expression has been reportedly up-regulated by vitamin D3 (VD3) in prostate cancer cells but has not been confirmed in pancreatic cancer cells. AIM: The study focuses on whether VD3 up-regulates PGDH expression in pancreatic cancer cells. METHODS: Human PaCa cell lines BxPC-3, HPAF-II and MIA PaCa-2 were treated with VD3 were analyzed for vitamin D receptor (VDR), cyclooxygenase-2 (COX-2) and PGDH expression by RT-PCR. Protein extracts were analyzed by Western blotting for VDR, COX-2, PGDH, SNAI1, SNAI2 and GAPDH expression. Cellular proliferation was analyzed by MTT assay. PGE2 was measured by ELISA. RESULTS: Dose-dependent treatment with VD3 at 1000 nM resulted in a maximal decrease in proliferation by 1.3 ± 0.1-fold in BxPC-3, 1.7 ± 0.3-fold in HPAF-II expressing elevated VDR and 1.1 ± 0.3-fold in MIA PaCa-2. VD3 at 10 nM resulted a time-dependent increase in PGDH mRNA expression by 3.8 ± 0.3-fold in BxPC-3 and 7.7 ± 0.6-fold in HPAF-II, whereas expression remained unchanged in MIA PaCa-2. Conversely, COX-2 mRNA expression decreased by 0.5 ± 0.1-fold in BxPC-3 and 0.6 ± 0.1-fold in HPAF-II, but not in MIA PaCa-2. PGDH protein expression increased at 96 and 120 hrs following treatment with VD3 in BxPC-3 and HPAF-II whereas COX-2 protein expression decreased in HPAF-II cells but was abolished by 96 and 120 hrs in BxPC-3 cells. PGDH protein expression was increased at 120 hrs in MIA PaCa-2 following addition of VD3 but COX-2 protein expression in this cell line was not detected. VD3 decreased the PGDH transcriptional regulators SNAI1 protein expression by 120 hrs in BxPC-3 and HPAF-II cells but not MIA PaCa-2 whereas SNAI2 decreased in all cell types by 96 hrs. Knockdown of SNAI by siRNA at 100 nM in HPAF-II resulted in a 1.3 ± 0.3-fold decrease proliferation and 1.4 ± 0.1-fold decrease in PGE2 production. Combined treatment with 100 nM of siSNAI and 10 nM of VD3 did not result in synergistic decrease in proliferation or PGE2 production. CONCLUSION: PaCa cells expressing vitamin D receptors responded to VD3 treatment with a corresponding increase in PGDH coupled with a decrease in COX-2 expression. VD3 or siSNAI resulted in a decrease in cellular proliferation and PGE2 production but the combined treatment did not augment further decreases, suggesting that the decrease by VD3 could be mediated through SNAI regulation of PGDH. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 62. doi:1538-7445.AM2012-62