Synthetic triterpenoid induces 15-PGDH expression and suppresses inflammation-driven colon carcinogenesis
Sung Hee Choi, … , Sanford D. Markowitz, John J. Letterio
Sung Hee Choi, … , Sanford D. Markowitz, John J. Letterio
Published May 16, 2014
Citation Information: J Clin Invest. 2014;124(6):2472-2482. https://doi.org/10.1172/JCI69672.
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Research Article Oncology

Synthetic triterpenoid induces 15-PGDH expression and suppresses inflammation-driven colon carcinogenesis

Abstract

Colitis-associated colon cancer (CAC) develops as a result of inflammation-induced epithelial transformation, which occurs in response to inflammatory cytokine-dependent downregulation of 15-hydroxyprostaglandin dehydrogenase (15-PGDH) and subsequent suppression of prostaglandin metabolism. Agents that both enhance 15-PGDH expression and suppress cyclooxygenase-2 (COX-2) production may more effectively prevent CAC. Synthetic triterpenoids are a class of small molecules that suppress COX-2 as well as inflammatory cytokine signaling. Here, we found that administration of the synthetic triterpenoid 2-cyano-3,12-dioxooleana-1,9(11)-dien-C28-methyl ester (CDDO-Me) suppresses CAC in mice. In a spontaneous, inflammation-driven intestinal neoplasia model, deletion of Smad4 specifically in T cells led to progressive production of inflammatory cytokines, including TNF-α, IFN-γ, iNOS, IL-6, IL-1β; as well as activation of STAT1 and STAT3; along with suppression of 15-PGDH expression. Oral administration of CDDO-Me to mice with SMAD4-deficient T cells increased survival and suppressed intestinal epithelial neoplasia by decreasing production of inflammatory mediators and increasing expression of 15-PGDH. Induction of 15-PGDH by CDDO-Me was dose dependent in epithelial cells and was abrogated following treatment with TGF-β signaling inhibitors in vitro. Furthermore, CDDO-Me–dependent 15-PGDH induction was not observed in Smad3–/– mice. Similarly, CDDO-Me suppressed azoxymethane plus dextran sodium sulfate–induced carcinogenesis in wild-type animals, highlighting the potential of small molecules of the triterpenoid family as effective agents for the chemoprevention of CAC in humans.

Authors

Sung Hee Choi, Byung-Gyu Kim, Janet Robinson, Steve Fink, Min Yan, Michael B. Sporn, Sanford D. Markowitz, John J. Letterio

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Figure 6

CDDO-Me increases the expression of 15-PGDH in colon epithelial cells.

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CDDO-Me increases the expression of 15-PGDH in colon epithelial cells. (...
(A) Expression of 15-PGDH protein and mRNA after treatment with CDDO-Me. FET cells were treated with various doses of CDDO-Me (0–300 nM) for 24 hours. Expression of 15-PGDH protein and mRNA was analyzed by Western blotting and RT-PCR analysis (β-actin was used as a control). Lanes were run on the same gel but were noncontiguous. The data shown are representative of 6 independent experiments. (B) Time-dependent effect of CDDO-Me (100 nM) on 15-PGDH expression. FET cells were treated with CDDO-Me (100 nM) for 6, 12, 24, 48, and 72 hours and analyzed by Western blot. The data shown are representative of 3 independent experiments. (C) CDDO-Me–induced 15-PGDH promoter luciferase activity. pGL3 and 15-PGDH promoter activity in FET cells following stimulation with CDDO-Me (300 nM) for 24 hours. The fold induction of the relative levels of 15-PGDH transcripts was compared with that of untreated pGL3 transcripts. A dual luciferase assay was performed, and data shown are averages of triplicate independent measurements of Firefly/Renilla luciferase readings normalized to untreated controls. Data represent average ± SEM (n = 4–6). (D) CDDO-Me inhibited colon epithelial cellular proliferation in a dose-dependent manner. 5 × 103 FET cells were cultured with CDDO-Me (0–300 nM) in 96-well plates with treatment, and proliferation was assessed by incorporation of 3H-thymidine.