In a significant fraction of breast cancer patients, distant metastases emerge after years or even decades of latency. How disseminated tumour cells (DTCs) are kept dormant, and what wakes them up, ...are fundamental problems in tumour biology. To address these questions, we used metastasis assays in mice and showed that dormant DTCs reside on microvasculature of lung, bone marrow and brain. We then engineered organotypic microvascular niches to determine whether endothelial cells directly influence breast cancer cell (BCC) growth. These models demonstrated that endothelial-derived thrombospondin-1 induces sustained BCC quiescence. This suppressive cue was lost in sprouting neovasculature; time-lapse analysis showed that sprouting vessels not only permit, but accelerate BCC outgrowth. We confirmed this surprising result in dormancy models and in zebrafish, and identified active TGF-β1 and periostin as tumour-promoting factors derived from endothelial tip cells. Our work reveals that stable microvasculature constitutes a dormant niche, whereas sprouting neovasculature sparks micrometastatic outgrowth.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Exosomes, small membrane vesicles （30-100 nm） of endocytic origin secreted by most cell types, contain functional biomolecules, which can be horizontally transferred to recipient cells 1. Exosomes ...bear a specific protein and lipid composition, and carry a select set of functional mRNAs and microRNAs 2. Recently, our group has shown that c-Met shed in exosomes can promote a proangiogenic and prometastatic phenotype in bone marrow-derived progenitor cells during melanoma progression 3. In previous research, retrotransposon RNA transcripts, single-stranded DNA （ssDNA）,
Cells from the myeloid lineage, namely macrophages, dendritic cells and osteoclasts, develop podosomes instead of stress fibers and focal adhesions to adhere and migrate. Podosomes share many ...components with focal adhesions but differ in their molecular organization, with a dense core of polymerized actin surrounded by scaffolding proteins, kinases and integrins. Podosomes are found either isolated both in macrophages and dendritic cells or arranged into superstructures in osteoclasts. When osteoclasts resorb bone, they form an F-actin rich sealing zone, which is a dense array of connected podosomes that firmly anchors osteoclasts to bone. It delineates a compartment in which protons and proteases are secreted to dissolve and degrade the mineralized matrix. Since Rho GTPases have been shown to control F-actin stress fibers and focal adhesions in mesenchymal cells, the question of whether they could also control podosome formation and arrangement in cells from the myeloid lineage, and particularly in osteoclasts, rapidly emerged. This article considers recent advances made in our understanding of podosome arrangements in osteoclasts and how Rho GTPases may control it.
An excess of osteoclastic bone resorption relative to osteoblastic bone formation results in progressive bone loss, characteristic of osteoporosis. Understanding the mechanisms of osteoclast ...differentiation is essential to develop novel therapeutic approaches to prevent and treat osteoporosis. We showed previously that Wrch1/RhoU is the only RhoGTPase whose expression is induced by RANKL during osteoclastogenesis. It associates with podosomes and the suppression of Wrch1 in osteoclast precursors leads to defective multinucleated cell formation. Here we further explore the functions of this RhoGTPase in osteoclasts, using RAW264.7 cells and bone marrow macrophages as osteoclast precursors. Suppression of Wrch1 did not prevent induction of classical osteoclastic markers such as NFATc1, Src, TRAP (Tartrate-Resistant Acid Phosphatase) or cathepsin K. ATP6v0d2 and DC-STAMP, which are essential for fusion, were also expressed normally. Similar to the effect of RANKL, we observed that Wrch1 expression increased osteoclast precursor aggregation and reduced their adhesion onto vitronectin but not onto fibronectin. We further found that Wrch1 could bind integrin ß3 cytoplasmic domain and interfered with adhesion-induced Pyk2 and paxillin phosphorylation. Wrch1 also acted as an inhibitor of M-CSF-induced prefusion osteoclast migration. In mature osteoclasts, high Wrch1 activity inhibited podosome belt formation. Nevertheless, it had no effect on mineralized matrix resorption. Our observations suggest that during osteoclastogenesis, Wrch1 potentially acts through the modulation of αvß3 signaling to regulate osteoclast precursor adhesion and migration and allow fusion. As an essential actor of osteoclast differentiation, the atypical RhoGTPase Wrch1/RhoU could be an interesting target for the development of novel antiresorptive drugs.
RhoGTPases regulate actin cytoskeleton dynamics, a key element in osteoclast biology. We identified three novel genes induced during RANKL‐stimulated osteoclastogenesis among RhoGTPases and their ...exchange factors that are essential in osteoclast biology.
Introduction: During the process of differentiation, adhesion to the bone matrix or osteolysis, the actin cytoskeleton of osteoclasts undergoes profound reorganization. RhoGTPases are key regulators of actin dynamics. They control cell adhesion, migration, and morphology through their action on actin cytoskeleton. In mice, there are 18 low molecular weight RhoGTPases. They are activated by guanine nucleotide exchange factors: the RhoGEFs. There are 76 RhoGEFs in mice: 65 belong to the Dbl family and 11 to the CZH family. To identify novel genes among RhoGTPases and RhoGEFs important in osteoclasts, we established the expression profiles of the complete families of RhoGTPases and RhoGEFs during RANKL‐stimulated osteoclastogenesis.
Materials and Methods: The RAW264.7 cell line, mouse bone marrow macrophages, and hematopoietic stem cells were used as precursors for RANKL‐induced osteoclastogenesis. Gene arrays and real‐time quantitative PCR analyses were performed to establish the transcription profiles of RhoGTPase and RhoGEF genes during differentiation. Small hairpin RNA was used to knock down genes of interest.
Results: Of the 18 RhoGTPases and 76 RhoGEFs, the expression of three genes was upregulated by RANKL: the RhoGTPase RhoU/Wrch1, the Dbl family exchange factor Arhgef8/Net1, and the CZH family exchange factor Dock5. The inductions were observed in gene array and real‐time quantitative PCR experiments performed in RAW264.7 cells. They were further confirmed in bone marrow macrophages and hematopoietic stem cells. Silencing of Wrch1 and Arhgef8 expression severely inhibited differentiation and affected osteoclast morphology. Dock5 suppression was lethal in osteoclast precursors while having no effect in fibroblasts.
Conclusions: We identified three genes among RhoGTPase signaling pathways that are upregulated during RANKL‐induced osteoclastogenesis. These genes are novel essential actors in osteoclasts, most likely through the control of actin cytoskeleton dynamics.
Background information. Rho GTPases are important regulators of cytoskeleton dynamics and cell adhesion. RhoU/Wrch‐1 is a Rho GTPase which shares sequence similarities with Rac1 and Cdc42 (cell ...division cycle 42), but has also extended N‐ and C‐terminal domains. The N‐terminal extension promotes binding to SH3 (Src homology 3)‐domain‐containing adaptors, whereas the C‐terminal extension mediates membrane targeting through palmitoylation of its non‐conventional CAAX box. RhoU/Wrch‐1 possesses transforming activity, which is negatively regulated by its N‐terminal extension and depends on palmitoylation.
Results. In the present study, we have shown that RhoU is localized to podosomes in osteoclasts and c‐Src‐expressing cells, and to focal adhesions of HeLa cells and fibroblasts. The N‐terminal extension and the palmitoylation site were dispensable, whereas the C‐terminal extension and effector binding loop were critical for RhoU targeting to focal adhesions. Moreover, the number of focal adhesions was reduced and their distribution changed upon expression of activated RhoU. Conversely, RhoU silencing increased the number of focal adhesions. As RhoU was only transiently associated with adhesion structures, this suggests that RhoU may modify adhesion turnover and cell migration rate. Indeed, we found that migration distances were increased in cells expressing activated RhoU and decreased when RhoU was knocked‐down.
Conclusions. Our data indicate that RhoU localizes to adhesion structures, regulates their number and distribution and increases cell motility. It also suggests that the RhoU effector binding and C‐terminal domains are critical for these functions.
Meiosis is characterized by two chromosome segregation rounds (meiosis I and II), which follow a single round of DNA replication, resulting in haploid genome formation. Chromosome reduction occurs at ...meiosis I. It relies on key structures, such as chiasmata, which are formed by repair of double-strand breaks (DSBs) between the homologous chromatids. In turn, to allow for segregation of homologs, chiasmata rely on the maintenance of sister chromatid cohesion. In most species, chiasma formation requires the prior synapsis of homologous chromosome axes, which is mediated by the synaptonemal complex, a tripartite proteinaceous structure specific to prophase I of meiosis. Yemanuclein (Yem) is a maternal factor that is crucial for sexual reproduction. It is required in the zygote for chromatin assembly of the male pronucleus, where it acts as a histone H3.3 chaperone in complex with Hira. We report here that Yem associates with the synaptonemal complex and the cohesin complex. A genetic interaction between yem(1) (V478E) and the Spo11 homolog mei-W68, modified a yem(1) dominant effect on crossover distribution, suggesting that Yem has an early role in meiotic recombination. This is further supported by the impact of yem mutations on DSB kinetics. A Hira mutation gave a similar effect, presumably through disruption of Hira-Yem complex.
Meiosis is characterized by two chromosome segregation rounds (Meiosis I and II), which follow a single round of DNA replication, resulting in haploid genome formation. Chromosome reduction occurs at ...meiosis I. It relies on key structures, such as chiasma, which is formed by repair between homologous chromatids of a double-strand break (DSB) in one of them; to function for segregation of homologues chiasma in turn relies on maintenance of sister chromatid cohesion. In most species, chiasma formation requires the prior synapsis of homologous chromosome axes, which is signaled by the Synaptonemal Complex (SC), a tripartite proteinaceous structure specific to prophase I of meiosis. Yemanuclein (YEM) is a maternal factor that is crucial for sexual reproduction. It is required in the zygote for chromatin assembly of the male pronucleus as a histone H3.3 chaperone in complex with HIRA. We report here YEM association to the SC and the cohesin complex. A genetic interaction between yem1 (V478E) and the Spo11 homologue mei-W68, added to a yem1 dominant effect on crossover distribution suggest an early role in meiotic recombination. This is further supported by the impact of yem mutations on DSB kinetics. Hira mutant showed a similar effect presumably through disruption of HIRA-YEM complex.
A central mechanism of tumour progression and metastasis involves the generation of an immunosuppressive 'macroenvironment' mediated in part through tumour-secreted factors. Here we demonstrate that ...upregulation of the Inhibitor of Differentiation 1 (Id1), in response to tumour-derived factors, such as TGFβ, is responsible for the switch from dendritic cell (DC) differentiation to myeloid-derived suppressor cell expansion during tumour progression. Genetic inactivation of Id1 largely corrects the myeloid imbalance, whereas Id1 overexpression in the absence of tumour-derived factors re-creates it. Id1 overexpression leads to systemic immunosuppression by downregulation of key molecules involved in DC differentiation and suppression of CD8 T-cell proliferation, thus promoting primary tumour growth and metastatic progression. Furthermore, advanced melanoma patients have increased plasma TGFβ levels and express higher levels of ID1 in myeloid peripheral blood cells. This study reveals a critical role for Id1 in suppressing the anti-tumour immune response during tumour progression and metastasis.
Antimicrobial resistance in wildlife Vittecoq, Marion; Godreuil, Sylvain; Prugnolle, Franck ...
Journal of applied ecology,
April 2016, Letnik:
53, Številka:
2
Journal Article
Recenzirano
Odprti dostop
1. The spread of antimicrobial resistance is of major concern for human health and leads to growing economic costs. While it is increasingly hypothesized that wildlife could play an important role in ...antimicrobial-resistant bacteria dynamics, empirical data remain scarce. 2. The present work builds on a systematic review of the available data in order to highlight the main information we have and to suggest research pathways that should be followed if we aim to fill the gaps in our current knowledge. 3. To achieve this goal, we address four questions: (i) Which resistant bacteria are the most frequently observed in wildlife? (ii) How are resistant bacteria exchanged between wildlife and the other hosts involved? (iii) In which habitats are those resistant bacteria found? (iv) Are resistances associated with certain ecological traits of the host? 4. Synthesis and applications. We highlight the strong link existing between the impact of human activities on natural habitats and the carriage of antimicrobial-resistant bacteria by wildlife. Furthermore, we underline that omnivorous, anthropophilic and carnivorous species are at high risk of being carriers and potentially spreaders of antimicrobial-resistant bacteria. Identifying among those groups key sentinel species may be of particular interest to implement ecosystem contamination surveillance. Finally, we discuss possible exchange routes for antimicrobial-resistant bacteria between humans and wildlife. Considering that water is of major importance in those exchanges, a critical way to control antimicrobial resistance spread may be to limit aquatic environment contamination by antimicrobial-resistant bacteria and antibiotics.
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