A vascular niche and a VEGF-Nrp1 loop regulate the initiation and stemness of skin tumours

Angiogenesis is critical during tumour initiation and malignant progression. Different strategies aimed at blocking vascular endothelial growth factor (VEGF) and its receptors have been developed to inhibit angiogenesis in cancer patients. It has become increasingly clear that in addition to its effect on angiogenesis, other mechanisms including a direct effect of VEGF on tumour cells may account for the efficiency of VEGF-blockade therapies. Cancer stem cells (CSCs) have been described in various cancers including squamous tumours of the skin. Here we use a mouse model of skin tumours to investigate the impact of the vascular niche and VEGF signalling on controlling the stemness (the ability to self renew and differentiate) of squamous skin tumours during the early stages of tumour progression. We show that CSCs of skin papillomas are localized in a perivascular niche, in the immediate vicinity of endothelial cells. Furthermore, blocking VEGFR2 caused tumour regression not only by decreasing the microvascular density, but also by reducing CSC pool size and impairing CSC renewal properties. Conditional deletion of Vegfa in tumour epithelial cells caused tumours to regress, whereas VEGF overexpression by tumour epithelial cells accelerated tumour growth. In addition to its well-known effect on angiogenesis, VEGF affected skin tumour growth by promoting cancer stemness and symmetric CSC division, leading to CSC expansion. Moreover, deletion of neuropilin-1 (Nrp1), a VEGF co-receptor expressed in cutaneous CSCs, blocked VEGF's ability to promote cancer stemness and renewal. Our results identify a dual role for tumour-cell-derived VEGF in promoting cancer stemness: by stimulating angiogenesis in a paracrine manner, VEGF creates a perivascular niche for CSCs, and by directly affecting CSCs through Nrp1 in an autocrine loop, VEGF stimulates cancer stemness and renewal. Finally, deletion of Nrp1 in normal epidermis prevents skin tumour initiation. These results may have important implications for the prevention and treatment of skin cancers.     

CCL2 recruits inflammatory monocytes to facilitate breast-tumour metastasis

Macrophages, which are abundant in the tumour microenvironment, enhance malignancy. At metastatic sites, a distinct population of metastasis-associated macrophages promotes the extravasation, seeding and persistent growth of tumour cells. Here we define the origin of these macrophages by showing that Gr1-positive inflammatory monocytes are preferentially recruited to pulmonary metastases but not to primary mammary tumours in mice. This process also occurs for human inflammatory monocytes in pulmonary metastases of human breast cancer cells. The recruitment of these inflammatory monocytes, which express CCR2 (the receptor for chemokine CCL2), as well as the subsequent recruitment of metastasis-associated macrophages and their interaction with metastasizing tumour cells, is dependent on CCL2 synthesized by both the tumour and the stroma. Inhibition of CCL2-CCR2 signalling blocks the recruitment of inflammatory monocytes, inhibits metastasis in vivo and prolongs the survival of tumour-bearing mice. Depletion of tumour-cell-derived CCL2 also inhibits metastatic seeding. Inflammatory monocytes promote the extravasation of tumour cells in a process that requires monocyte-derived vascular endothelial growth factor. CCL2 expression and macrophage infiltration are correlated with poor prognosis and metastatic disease in human breast cancer. Our data provide the mechanistic link between these two clinical associations and indicate new therapeutic targets for treating metastatic breast cancer.     

Experimental infection of bats with Geomyces destructans causes white-nose syndrome

White-nose syndrome (WNS) has caused recent catastrophic declines among multiple species of bats in eastern North America. The disease's name derives from a visually apparent white growth of the newly discovered fungus Geomyces destructans on the skin (including the muzzle) of hibernating bats. Colonization of skin by this fungus is associated with characteristic cutaneous lesions that are the only consistent pathological finding related to WNS. However, the role of G. destructans in WNS remains controversial because evidence to implicate the fungus as the primary cause of this disease is lacking. The debate is fuelled, in part, by the assumption that fungal infections in mammals are most commonly associated with immune system dysfunction. Additionally, the recent discovery that G. destructans commonly colonizes the skin of bats of Europe, where no unusual bat mortality events have been reported, has generated further speculation that the fungus is an opportunistic pathogen and that other unidentified factors are the primary cause of WNS. Here we demonstrate that exposure of healthy little brown bats (Myotis lucifugus) to pure cultures of G. destructans causes WNS. Live G. destructans was subsequently cultured from diseased bats, successfully fulfilling established criteria for the determination of G. destructans as a primary pathogen. We also confirmed that WNS can be transmitted from infected bats to healthy bats through direct contact. Our results provide the first direct evidence that G. destructans is the causal agent of WNS and that the recent emergence of WNS in North America may represent translocation of the fungus to a region with a naive population of animals. Demonstration of causality is an instrumental step in elucidating the pathogenesis and epidemiology of WNS and in guiding management actions to preserve bat populations against the novel threat posed by this devastating infectious disease.     

A closely packed system of low-mass, low-density planets transiting Kepler-11

When an extrasolar planet passes in front of (transits) its star, its radius can be measured from the decrease in starlight and its orbital period from the time between transits. Multiple planets transiting the same star reveal much more: period ratios determine stability and dynamics, mutual gravitational interactions reflect planet masses and orbital shapes, and the fraction of transiting planets observed as multiples has implications for the planarity of planetary systems. But few stars have more than one known transiting planet, and none has more than three. Here we report Kepler spacecraft observations of a single Sun-like star, which we call Kepler-11, that reveal six transiting planets, five with orbital periods between 10 and 47?days and a sixth planet with a longer period. The five inner planets are among the smallest for which mass and size have both been measured, and these measurements imply substantial envelopes of light gases. The degree of coplanarity and proximity of the planetary orbits imply energy dissipation near the end of planet formation.     

Human metabolic individuality in biomedical and pharmaceutical research

Genome-wide association studies (GWAS) have identified many risk loci for complex diseases, but effect sizes are typically small and information on the underlying biological processes is often lacking. Associations with metabolic traits as functional intermediates can overcome these problems and potentially inform individualized therapy. Here we report a comprehensive analysis of genotype-dependent metabolic phenotypes using a GWAS with non-targeted metabolomics. We identified 37 genetic loci associated with blood metabolite concentrations, of which 25 show effect sizes that are unusually high for GWAS and account for 10-60% differences in metabolite levels per allele copy. Our associations provide new functional insights for many disease-related associations that have been reported in previous studies, including those for cardiovascular and kidney disorders, type 2 diabetes, cancer, gout, venous thromboembolism and Crohn's disease. The study advances our knowledge of the genetic basis of metabolic individuality in humans and generates many new hypotheses for biomedical and pharmaceutical research.