SUMMARY Inflammatory bowel disease is an important risk factor for colorectal cancer. We show that sphingosine-1-phosphate (S1P) produced by upregulation of sphingosine kinase 1 (SphK1) links chronic intestinal inflammation to colitis-associated cancer (CAC) and both are exacerbated by deletion of Sphk2. S1P is essential for production of the multifunctional NF-κB-regulated cytokine IL-6, persistent activation of the transcription factor STAT3, and consequent upregulation of the S1P receptor, S1PR1. The pro-drug FTY720 decreased SphK1 and S1PR1 expression and eliminated the NF-κB/IL-6/STAT3 amplification cascade and development of CAC even in Sphk2−/− mice and may be useful in treating colon cancer in individuals with ulcerative colitis. Thus, the SphK1/S1P/S1PR1 axis is at the nexus between NF-κB and STAT3 and connects chronic inflammation and CAC.

FTY720 (fingolimod), an FDA-approved drug for treatment of multiple sclerosis, has beneficial effects in the CNS that are not yet well understood, independent of its effects on immune cell trafficking. We show that FTY720 enters the nucleus, where it is phosphorylated by sphingosine kinase 2 (SphK2), and that nuclear FTY720-P binds and inhibits class I histone deacetylases (HDACs), enhancing specific histone acetylations. FTY720 is also phosphorylated in mice and accumulates in the brain, including the hippocampus, inhibits HDACs and enhances histone acetylation and gene expression programs associated with memory and learning, and rescues memory deficits independently of its immunosuppressive actions. Sphk2−/− mice have lower levels of hippocampal sphingosine-1-phosphate, an endogenous HDAC inhibitor, and reduced histone acetylation, and display deficits in spatial memory and impaired contextual fear extinction. Thus, sphingosine-1-phosphate and SphK2 play specific roles in memory functions and FTY720 may be a useful adjuvant therapy to facilitate extinction of aversive memories.

Background Asthma, a chronic inflammatory condition defined by episodic shortness of breath with expiratory wheezing and cough, is a serious health concern affecting more than 250 million persons. Genome-wide association studies have identified ORM (yeast)–like protein isoform 3 (ORMDL3) as a gene associated with susceptibility to asthma. Although its yeast ortholog is a negative regulator of de novo ceramide biosynthesis, how ORMDL3 contributes to asthma pathogenesis is not known. Objectives We sought to decipher the molecular mechanism for the pathologic functions of ORMDL3 in asthma and the relationship to its evolutionarily conserved role in regulation of ceramide homeostasis. Methods We determined the relationship between expression of ORMDL3 and ceramide in epithelial and inflammatory cells and in asthma pathogenesis in mice. Results Although small increases in ORMDL3 expression decrease ceramide levels, remarkably, higher expression in lung epithelial cells and macrophages in vitro and in vivo increased ceramide production, which promoted chronic inflammation, airway hyperresponsiveness, and mucus production during house dust mite–induced allergic asthma. Moreover, nasal administration of the immunosuppressant drug FTY720/fingolimod reduced ORMDL3 expression and ceramide levels and mitigated airway inflammation and hyperreactivity and mucus hypersecretion in house dust mite–challenged mice. Conclusions Our findings demonstrate that overexpression of ORMDL3 regulates ceramide homeostasis in cells in a complex manner and suggest that local FTY720 administration might be a useful therapeutic intervention for the control of allergic asthma.

Estrogen receptor-α (ERα)-negative breast cancer is clinically aggressive and does not respond to conventional hormonal therapies. Strategies that lead to re-expression of ERα could sensitize ERα-negative breast cancers to selective ER modulators. FTY720 (fingolimod, Gilenya), a sphingosine analog, is the Food and Drug Administration (FDA)-approved prodrug for treatment of multiple sclerosis that also has anticancer actions that are not yet well understood. We found that FTY720 is phosphorylated in breast cancer cells by nuclear sphingosine kinase 2 and accumulates there. Nuclear FTY720-P is a potent inhibitor of class I histone deacetylases (HDACs) that enhances histone acetylations and regulates expression of a restricted set of genes independently of its known effects on canonical signaling through sphingosine-1-phosphate receptors. High-fat diet (HFD) and obesity, which is now endemic, increase breast cancer risk and have been associated with worse prognosis. HFD accelerated the onset of tumors with more advanced lesions and increased triple-negative spontaneous breast tumors and HDAC activity in MMTV-PyMT transgenic mice. Oral administration of clinically relevant doses of FTY720 suppressed development, progression and aggressiveness of spontaneous breast tumors in these mice, reduced HDAC activity and strikingly reversed HFD-induced loss of estrogen and progesterone receptors in advanced carcinoma. In ERα-negative human and murine breast cancer cells, FTY720 reactivated expression of silenced ERα and sensitized them to tamoxifen. Moreover, treatment with FTY720 also re-expressed ERα and increased therapeutic sensitivity of ERα-negative syngeneic breast tumors to tamoxifen in vivo more potently than a known HDAC inhibitor. Our work suggests that a multipronged attack with FTY720 is a novel combination approach for effective treatment of both conventional hormonal therapy-resistant breast cancer and triple-negative breast cancer.

Background: ApoM overexpression in nonhepatic cells generates larger nascent HDLs. Results: Hepatocyte-specific apoM transgenic mice have larger plasma HDLs and hepatocytes that generate larger nascent HDLs and increased S1P secretion. Conclusion: Hepatocyte-specific apoM overexpression facilitates large apoM/S1P-enriched HDL formation by promoting large nascent HDL formation and stimulating sphingolipid synthesis and S1P secretion. Significance: Hepatic apoM regulates HDL and S1P production.