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Cancer-produced metabolites of 5-lipoxygenase induce tumor-evoked Bregs via peroxisome proliferator-activated receptor alpha

ABSTRACT: Breast cancer cells facilitate distant metastasis through the induction of immunosuppressive regulatory B cells, designated tBregs. We report here that, to do this, breast cancer cells produce metabolites of the 5-lipoxygenase (5-LO) pathway such as leukotriene B4 (LTB4) to activate the proliferator-activated receptor alpha (PPARalpha) in B cells. Inactivation of LTB4 signaling or genetic deficiency of PPARalpha in B cells blocks the generation of tBregs and thereby abrogates lung metastasis in mice with established breast cancer. Thus, in addition to eliciting fatty acid oxidation and metabolic signals, PPARalpha initiates programs required for differentiation of tBregs. We propose that PPARalpha in B cells or/and tumor 5-LO pathways represents new targets for pharmacological control of tBreg-mediated cancer escape.

OTHER RELATED OMICS DATASETS IN: PRJNA185262

ORGANISM(S): Mus musculus

PROVIDER: GSE43278 | GEO | 2013/03/13

SECONDARY ACCESSION(S): PRJNA185262

REPOSITORIES: GEO

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Project description:Bmpr2 mutations are critical risk factors for hereditary pulmonary arterial hypertension (hPAH) with approximately 20% of carriers developing disease. There is an unmet medical need to understand how environmental factors, such as inflammation, render Bmpr2 mutants susceptible to PAH. Overexpressing 5-lipoxygenase (5-LO) provokes lung inflammation and transient PAH in Bmpr2+/- mice. Accordingly, 5-LO and its metabolite, leukotriene B4 (LTB4), are candidates for the ‘second hit’. The purpose of this study was to determine how 5-LO-mediated pulmonary inflammation synergized with phenotypically-silent Bmpr2 defects to elicit significant pulmonary vascular disease in rats. Monoallelic Bmpr2 mutant rats were generated and found phenotypically normal for up to one year of observation. To evaluate whether a second hit would elicit disease, animals were exposed to 5-LO-expressing adenovirus (AdAlox5), monocrotaline, SU5416 or chronic hypoxia and analyzed. Bmpr2-mutant hPAH patient samples were assessed for neointimal 5-LO expression. Pulmonary artery endothelial cells (PAECs) were cultured with lentivirus expressing short hairpin RNA (shRNA) targeting Bmpr2 (shBmpr2) to model the impaired BMPR2 signaling, and were then exposed to 5-LO-expressing adenovirus (AdAlox5), and were assessed for phenotypic and transcriptomic changes. In vitro, BMPR2 deficiency, compounded by 5-LO-mediated inflammation, generated apoptosis-resistant and proliferative PAECs with mesenchymal characteristics. These transformed cells expressed nuclear envelop-localized 5-LO consistent with induced LTB4 production, as well as a transcriptomic signature similar to clinical disease, including upregulated NF-kB, IL-6 and TGF-β signaling pathways. The reversal of PAH and vasculopathy in Bmpr2 mutants by TGF-β antagonism suggests that TGF-β is critical for neointimal transformation. Thus, in a new two-hit model of disease, lung inflammation induced severe PAH pathology in Bmpr2+/- rats. Endothelial transformation required the activation of canonical and noncanonical TGF-β signaling pathways and was characterized by 5-LO nuclear envelope translocation with enhanced LTB4 production. This study offers one explanation of how an environmental injury unleashes the destructive potential of an otherwise-silent genetic mutation.

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Cancer-produced metabolites of 5-lipoxygenase induce tumor-evoked Bregs via peroxisome proliferator-activated receptor alpha

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