Obesity and elevated circulating cholesterol are risk factors for breast cancer recurrence, while the use of statins, cholesterol biosynthesis inhibitors widely used for treating hypercholesterolemia, is associated with improved disease-free survival. Here, we show that cholesterol mediates the metastatic effects of a high-fat diet via its oxysterol metabolite, 27-hydroxycholesterol. Ablation or inhibition of CYP27A1, the enzyme responsible for the rate-limiting step in 27-hydroxycholesterol biosynthesis, significantly reduces metastasis in relevant animal models of cancer. The robust effects of 27-hydroxycholesterol on metastasis requires myeloid immune cell function, and it was found that this oxysterol increases the number of polymorphonuclear-neutrophils and γδ-T cells at distal metastatic sites. The pro-metastatic actions of 27-hydroxycholesterol requires both polymorphonuclear-neutrophils and γδ-T cells, and 27-hydroxycholesterol treatment results in a decreased number of cytotoxic CD8+T lymphocytes. Therefore, through its actions on γδ-T cells and polymorphonuclear-neutrophils, 27-hydroxycholesterol functions as a biochemical mediator of the metastatic effects of hypercholesterolemia.

Tumor-associated myeloid cells regulate tumor growth and metastasis, and their accumulation is a negative prognostic factor for breast cancer. Here we find calcium/calmodulin-dependent kinase kinase (CaMKK2) to be highly expressed within intratumoral myeloid cells in mouse models of breast cancer, and demonstrate that its inhibition within myeloid cells suppresses tumor growth by increasing intratumoral accumulation of effector CD8 + T cells and immune-stimulatory myeloid subsets. Tumor-associated macrophages (TAMs) isolated from Camkk2 −/− mice expressed higher levels of chemokines involved in the recruitment of effector T cells compared to WT. Similarly, in vitro generated Camkk2 −/− macrophages recruit more T cells, and have a reduced capability to suppress T cell proliferation, compared to WT. Treatment with CaMKK2 inhibitors blocks tumor growth in a CD8 + T cell-dependent manner, and facilitates a favorable reprogramming of the immune cell microenvironment. These data, credential CaMKK2 as a myeloid-selective checkpoint, the inhibition of which may have utility in the immunotherapy of breast cancer.

CD39 is a transmembrane enzyme that inhibits platelet reactivity and inflammation by phosphohydrolyzing ATP and ADP to AMP. Cyclic AMP (cAMP), an essential second messenger, is particularly important in regulating genes controlling vascular homeostasis. These experiments test the hypothesis that cAMP might positively regulate the expression of CD39 and thereby modulate important vascular homeostatic properties.

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As the most common cancer in women, one in eight will develop invasive breast cancer over their lifetime making it the second most common cause of cancer-related death among women. Of the many known risk factors for developing breast cancer, obesity stands out as prominent and modifiable. Interestingly, elevated cholesterol is highly associated with obesity, and has emerged as an independent risk factor for breast cancer onset and recurrence. This indicates that cholesterol also contributes to the breast cancer-pathogenicity of obesity. This review highlights our current understanding of the mechanisms by which cholesterol impacts breast cancer. Key preclinical studies have been highlighted, including discussion of homeostatic control of cholesterol levels, signaling by cholesterol metabolites through the estrogen receptors, cholesterol formation of lipid rafts and subsequent signaling, and the potential roles of cholesterol in creating a pro-inflammatory tumor microenvironment. Future directions and avenues for therapeutic exploitation are also considered.

BackgroundRecent studies have indicated the presence of multipotent mesenchymal stromal cells (MSCs) in human lung diseases. Excess airway smooth muscle, myofibroblasts and activated fibroblasts have each been noted in asthma, suggesting that mesenchymal progenitor cells play a role in asthma pathogenesis. We therefore sought to determine whether MSCs are present in the lungs of ovalbumin (OVA)-sensitized and challenged mice, a model of allergic airways disease.MethodsBalb/c mice were sensitized and challenged with PBS or OVA over a 25 day period. Flow cytometry as well as colony forming and differentiation potential were used to analyze the emergence of MSCs along with gene expression studies using immunochemical analyses, quantitative polymerase chain reaction (qPCR), and gene expression beadchips.ResultsA CD45-negative subset of cells expressed Stro-1, Sca-1, CD73 and CD105. Selection for these markers and negative selection against CD45 yielded a population of cells capable of adipogenic, osteogenic and chondrogenic differentiation. Lungs from OVA-treated mice demonstrated a greater average colony forming unit-fibroblast (CFU-F) than control mice. Sorted cells differed from unsorted lung adherent cells, exhibiting a pattern of gene expression nearly identical to bone marrow-derived sorted cells. Finally, cells isolated from the bronchoalveolar lavage of a human asthma patient showed identical patterns of cell surface markers and differentiation potential.ConclusionsIn summary, allergen sensitization and challenge is accompanied by an increase of MSCs resident in the lungs that may regulate inflammatory and fibrotic responses.

There is an urgent need for more effective strategies to treat ovarian cancer. Elevated cholesterol levels are associated with a decreased progression-free survival time (PFS) while statins are protective. 27-Hydroxycholesterol (27HC), a primary metabolite of cholesterol, has been shown to modulate the activities of the estrogen receptors (ERs) and liver x receptors (LXRs) providing a potential mechanistic link between cholesterol and ovarian cancer progression. We found that high expression of CYP27A1, the enzyme responsible for the synthesis of 27HC, was associated with decreased PFS, while high expression of CYP7B1, responsible for 27HC catabolism, was associated with increased PFS. However, 27HC decreased the cellular proliferation of various ovarian cancer cell lines in an LXR-dependent manner. Intriguingly, ID8 grafts were unable to effectively establish in CYP27A1−/− mice, indicating involvement of the host environment. Tumors from mice treated with 27HC had altered myeloid cell composition, and cells from the marrow stem cell lineage were found to be responsible for the effects in CYP27A1−/− mice. While inhibition of CYP27A1 or immune checkpoint did not significantly alter tumor size, their combination did, thereby highlighting this axis as a therapeutic target.