Sphingosine-1-phosphate lyase downregulation promotes colon carcinogenesis through STAT3-activated microRNAs
Emilie Degagné, … , Yasmin Ahmedi, Julie D. Saba
Emilie Degagné, … , Yasmin Ahmedi, Julie D. Saba
Published October 27, 2014
Citation Information: J Clin Invest. 2014;124(12):5368-5384. https://doi.org/10.1172/JCI74188.
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Research Article Oncology

Sphingosine-1-phosphate lyase downregulation promotes colon carcinogenesis through STAT3-activated microRNAs

Abstract

Growing evidence supports a link between inflammation and cancer; however, mediators of the transition between inflammation and carcinogenesis remain incompletely understood. Sphingosine-1-phosphate (S1P) lyase (SPL) irreversibly degrades the bioactive sphingolipid S1P and is highly expressed in enterocytes but downregulated in colon cancer. Here, we investigated the role of SPL in colitis-associated cancer (CAC). We generated mice with intestinal epithelium-specific Sgpl1 deletion and chemically induced colitis and tumor formation in these animals. Compared with control animals, mice lacking intestinal SPL exhibited greater disease activity, colon shortening, cytokine levels, S1P accumulation, tumors, STAT3 activation, STAT3-activated microRNAs (miRNAs), and suppression of miR-targeted anti-oncogene products. This phenotype was attenuated by STAT3 inhibition. In fibroblasts, silencing SPL promoted tumorigenic transformation through a pathway involving extracellular transport of S1P through S1P transporter spinster homolog 2 (SPNS2), S1P receptor activation, JAK2/STAT3-dependent miR-181b-1 induction, and silencing of miR-181b-1 target cylindromatosis (CYLD). Colon biopsies from patients with inflammatory bowel disease revealed enhanced S1P and STAT3 signaling. In mice with chemical-induced CAC, oral administration of plant-type sphingolipids called sphingadienes increased colonic SPL levels and reduced S1P levels, STAT3 signaling, cytokine levels, and tumorigenesis, indicating that SPL prevents transformation and carcinogenesis. Together, our results suggest that dietary sphingolipids can augment or prevent colon cancer, depending upon whether they are metabolized to S1P or promote S1P metabolism through the actions of SPL.

Authors

Emilie Degagné, Ashok Pandurangan, Padmavathi Bandhuvula, Ashok Kumar, Abeer Eltanawy, Meng Zhang, Yuko Yoshinaga, Mikhail Nefedov, Pieter J. de Jong, Loren G. Fong, Stephen G. Young, Robert Bittman, Yasmin Ahmedi, Julie D. Saba

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Figure 6

SPL downregulation promotes cell transformation in a STAT3-dependent manner.

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SPL downregulation promotes cell transformation in a STAT3-dependent man...
(A) IB of SPL and STAT3 expression in Stat3+/+ and Stat3–/– MEFs in which SPL was silenced (SPL knockdown) compared with vector-only control (C) cell lines. (B) Intracellular and (C) extracellular S1P levels in MEF lines. (D) Spns2 mRNA expression levels in MEF lines. (E) Extracellular S1P levels in Stat3+/+ SPL knockdown MEFs with or without SPNS2 siRNA and MEF Stat3+/+ control cells. (F) Cell proliferation at day 3 of MEFs grown in 0% FBS in Stat3+/+ SPL knockdown MEFs with and without SPNS2 siRNA and MEF Stat3+/+ control cells. Representative bar graph from 1 individual experiment is shown. Statistical analysis was performed with data from 3 independent experiments. (G) Il6 mRNA expression levels in MEF lines. (H) Protein expression of activated JAK-2 (JAK2-P), total JAK-2 (JAK2-T), activated STAT3 (STAT3-P), and total STAT3 (STAT3-T) in control and SPL knockdown Stat3+/+ MEFs, following treatment with 125 nM S1P. (I) Cell proliferation of MEFs grown in 0% FBS. (J) Time course of tumor growth, following s.c. injection of MEF cell lines into NOD/SCID mice. Blots shown are from different gels. (K) miR-181b-1 expression and (L) Cyld expression in tumors or injection sites of NOD/SCID mice. (M) Cell proliferation at day 3 of MEFs grown in 0% FBS with or without W123 (10 μM), FTY720 (100 nm), rolipram (10 μM), NSC 74859 (25 μM), and WP1066 (1 μM) added at day 0. *P < 0.05 compared with control Stat3+/+ MEFs. #P < 0.05 compared with control SPL knockdown Stat3+/+ MEFs.