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 7

Induction of 15-PGDH expression by CDDO-Me requires SMAD-dependent TGF-β signaling.

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Induction of 15-PGDH expression by CDDO-Me requires SMAD-dependent TGF-β...
(A) FET cells cultured with CDDO-Me plus TGF-β (1 ng/ml). Western blot is representative of 3 independent experiments (noncontiguous lanes were run on the same gel). Graphs represent the mean ± SEM of 4 independent sets of experiments. (B) FET cells transfected with SBE-luc were treated with CDDO-Me plus TGF-β (1 ng/ml). Results of a dual luciferase assay are shown as averages (triplicate independent measurements of Firefly/Renilla luciferase normalized to untreated controls). Results are representative of 3 different experiments. (C) FET cells were treated with either TGF-β or CDDO-Me (for 10 minutes to 9 hours) and phosphorylation of SMAD2 and SMAD3 was examined by Western blot. (D) Cells were incubated for 30 minutes with either TGF-β receptor inhibitors, SB431542 (10 μM) or IN1130 (10 μM), or SMAD3-specific inhibitor, SIS3 (10 μM), before adding TGF-β (1 ng/ml) and/or CDDO-Me (300 nM). Data represent 3 independent experiments (all noncontiguous lanes were run on the same gel). (E) CDDO-Me failed to induce mucosal 15-PGDH expression in vivo in SMAD3 KO mice. Mice received CDDO-Me (1.25 μg or 5 μg) by gavage, and colon epithelial scrapings were analyzed by Western blot 24 hours after the last dose (all noncontiguous lanes were run on the same gel). (F) Proliferation of FET cells (with or without CDDO-Me and/or TGF-β) was measured by incorporation of 3H-thymidine.