Due to its ability to inhibit pro-metastatic matrix metalloproteinases, tissue inhibitor of metalloproteinases (TIMP)-1 has been thought to suppress tumor metastasis. However, elevated systemic levels of TIMP-1 correlate with poor prognosis in cancer patients suggesting a metastasis-stimulating role of TIMP-1. In colorectal cancer patients, tumor as well as plasma TIMP-1 levels were correlated with synchronous liver metastasis or distant metastasis-associated disease relapse. In mice, high systemic TIMP-1 levels increased the liver susceptibility towards metastasis by triggering the formation of a pre-metastatic niche. This promoted hepatic metastasis independent of origin or intrinsic metastatic potential of tumor cells. High systemic TIMP-1 led to increased hepatic SDF-1 levels, which in turn promoted recruitment of neutrophils to the liver. Both inhibition of SDF-1-mediated neutrophil recruitment and systemic depletion of neutrophils reduced TIMP-1-induced increased liver susceptibility towards metastasis. This indicates a crucial functional role of neutrophils in the TIMP-1-induced pre-metastatic niche. Conclusion Our results identify TIMP-1 as an essential promoter of hepatic pre-metastatic niche formation.

Tissue inhibitor of metalloproteinases-1 (TIMP-1) recently emerged as a pro-metastatic factor highly associated with poor prognosis in a number of cancers. This correlation seemed paradox as TIMP-1 is best described as an inhibitor of pro-tumourigenic matrix metalloproteinases. Only recently, TIMP-1 has been revealed as a signalling molecule that can regulate cancer progression independent of its inhibitory properties. In the present study, we demonstrate that an increase of both exogenous and endogenous TIMP-1 led to the upregulation of miR-210 in a CD63/PI3K/AKT/HIF-1-dependent pathway in lung adenocarcinoma cells. TIMP-1 induced P110/P85 PI3K-signalling and AKT phosphorylation. It also led to increase of HIF-1α protein levels positively correlating with HIF-1-regulated mRNA expression and upregulation of the microRNA miR-210. Downstream targets of miR-210, namely FGFRL1, E2F3, VMP-1, RAD52 and SDHD, were decreased in the presence of TIMP-1. Upon the overexpression of TIMP-1 in tumour cells, miR-210 was accumulated in exosomes in vitro and in vivo. These exosomes promoted tube formation activity in human umbilical vein endothelial cell (HUVECs), which was reflected in increased angiogenesis in A549L-derived tumour xenografts. Activation and elevation of PI3K, AKT, HIF-1A and miR-210 in tumours additionally confirmed our in vitro data. This new pro-tumourigenic signalling function of TIMP-1 may explain why elevated TIMP-1 levels in lung cancer patients are highly correlated with poor prognosis.

The ubiquitin-proteasome system (UPS) has been successfully targeted by both academia and the pharmaceutical industry for oncological and immunological applications. Typical proteasome inhibitors are based on a peptidic backbone endowed with an electrophilic C-terminus by which they react with the active proteolytic sites. Although the peptide moiety has attracted much attention in terms of subunit selectivity, the target specificity and biological stability of the compounds are largely determined by the reactive warheads. In this study, we have carried out a systematic investigation of described electrophiles by a combination of in vitro, in vivo, and structural methods in order to disclose the implications of altered functionality and chemical reactivity. Thereby, we were able to introduce and characterize the class of α-ketoamides as the most potent reversible inhibitors with possible applications for the therapy of solid tumors as well as autoimmune disorders.

The concept of proteasome inhibition ranks among the latest achievements in the treatment of blood cancer and represents a promising strategy for modulating autoimmune diseases. In this study, we describe peptidic sulfonyl fluoride inhibitors that selectively block the catalytic β5 subunit of the immunoproteasome by inducing only marginal cytotoxic effects. Structural and mass spectrometric analyses revealed a novel reaction mechanism involving polarity inversion and irreversible crosslinking of the proteasomal active site. We thus identified the sulfonyl fluoride headgroup for the development and optimization of immunoproteasome selective compounds and their possible application in autoimmune disorders.

During mRNA translation, tRNAs are charged by aminoacyl-tRNA synthetases and subsequently used by ribosomes. A multi-enzyme aminoacyl-tRNA synthetase complex (MSC) has been proposed to increase protein synthesis efficiency by passing charged tRNAs to ribosomes. An alternative function is that the MSC repurposes specific synthetases that are released from the MSC upon cues for functions independent of translation. To explore this, we generated mammalian cells in which arginyl-tRNA synthetase and/or glutaminyl-tRNA synthetase were absent from the MSC. Protein synthesis, under a variety of stress conditions, was unchanged. Most strikingly, levels of charged tRNAArg and tRNAGln remained unchanged and no ribosome pausing was observed at codons for arginine and glutamine. Thus, increasing or regulating protein synthesis efficiency is not dependent on arginyl-tRNA synthetase and glutaminyl-tRNA synthetase in the MSC. Alternatively, and consistent with previously reported ex-translational roles requiring changes in synthetase cellular localizations, our manipulations of the MSC visibly changed localization.

Protein activity is often regulated by altering the oligomerization state. One mechanism of multimerization involves domain swapping, wherein proteins exchange parts of their structures and thereby form long-lived dimers or multimers. Domain swapping has been specifically observed in amyloidogenic proteins, for example the cystatin superfamily of cysteine protease inhibitors. Cystatins are twin-headed inhibitors, simultaneously targeting the lysosomal cathepsins and legumain, with important roles in cancer progression and Alzheimer's disease. Although cystatin E is the most potent legumain inhibitor identified so far, nothing is known about its propensity to oligomerize. In this study, we show that conformational destabilization of cystatin E leads to the formation of a domain-swapped dimer with increased conformational stability. This dimer was active as a legumain inhibitor by forming a trimeric complex. By contrast, the binding sites toward papain-like proteases were buried within the cystatin E dimer. We also showed that the dimers could further convert to amyloid fibrils. Unexpectedly, cystatin E amyloid fibrils contained functional protein, which inhibited both legumain and papain-like enzymes. Fibril formation was further regulated by glycosylation. We speculate that cystatin amyloid fibrils might serve as a binding platform to stabilize the pH-sensitive legumain and cathepsins in the extracellular environment, contributing to their physiological and pathological functions.

© F e r r a t a S t o r t i F o u n d a t i o nrent study, we investigated whether TIMP-1 affects neutrophil homeostasis. We show that TIMP-1 signaling via CD63 triggered granulopoiesis in the bone marrow (BM) resulting in increased systemic neutrophil blood counts. Our findings reveal a new function of TIMP-1 on immune cell homeostasis, and may provide a link to the frequently described correlation of high TIMP-1 levels with inflammatory diseases in the clinic. Methods Animal experimentsAnimal experiments were performed in compliance with the guidelines of the Tierschutzgesetz des Freistaates Bayern and approved by the Regierung von Oberbayern. For TIMP-1-secreting tumors, 2x10 6 HT1080 cells were subcutaneously injected into the nuchal fold of CD1 nu/nu mice and tumors were grown over ten days to a diameter of approximately 1 cm. Tumor size was monitored with a caliper. For adenoviral transduction, 3x10 9 ifu were intravenously injected, as previously described. 22 Recombinant TIMP-1 protein was applied in LPS-free PBS by a single intraperitoneal (i.p.) injection of 2 mg/kg, as previously described. 22 Mice were killed with CO 2 , blood was collected from the vena cava inferior using EDTA-coated syringes, and BM cells were obtained by flushing femurs and tibias with PBS. Flow cytometryAbsolute quantification of blood neutrophils occurred in BD trucount TM tubes according to the manufacturer´s instructions. Briefly, antibody-cocktail was mixed with 50 mL fresh blood in trucount TM tubes and incubated for 15 min at RT. Subsequently, 450 mL FACS TM lysing solution (BD Bioscience) were added and incubated for 30 min at RT to lyse erythrocytes and fix the sample. For staining of BM, femurs and tibias were flushed with PBS and the obtained cell suspension was stained as blood. Samples were measured on a FACS Canto TM II flow cytometer (BD) and analyzed using FlowJo software. Immunohistochemical staining of neutrophilsFor immunohistochemical analysis of BM, femurs were freed from tissue, fixed in 4% paraformaldehyde for 20 h, de-calcified in 0.5 M EDTA for five days, dehydrated and embedded into paraffin. Ly6G-positive cells were stained on 4 mm sections, as previously described. 22 Colony formation assayBone marrow cells were harvested from AdCtrl or AdT1-transduced mice and erythrocytes were removed with RBC lysis buffer (eBioscience). 1x10 4 BM cells were seeded in MethoCult TM medium (StemCell Technologies) containing 50 ng/mL murine rSCF, 10 ng/mL murine rIL-3, and 10 ng/mL murine rIL-6 into 6-well plates. Cells were incubated at 37°C for seven days and colonies per well were counted. For each mouse, analysis was performed in duplicates, and a total of 5 mice per group were analyzed. 32Dcl3 differentiation assay 32Dcl3 cells were seeded at a density of 8x10 5 cells/mL in IL3-free medium supplemented with 100 ng/mL murine G-CSF (Peptrotech) +/-1000 ng/mL rTIMP-1. Every two days, medium was replaced by fresh medium containing 50 ng/mL G-CSF +/-1000 ng/mL rTIMP-1. At the indicated time points, cells were c...

In contrast to expectations in the past that tumor starvation or unselective inhibition of proteolytic activity would cure cancer, there is accumulating evidence that microenvironmental stress, such as hypoxia or broad-spectrum inhibition of metalloproteinases can promote metastasis. In fact, malignant tumor cells, due to their genetic and epigenetic instability, are predisposed to react to stress by adaptation and, if the stress persists, by escape and formation of metastasis. Recent recognition of the concepts of dynamic evolution as well as population and systems biology is extremely helpful to understand the disappointments of clinical trials with new drugs and may lead to paradigm-shifts in therapy strategies. This must be complemented by an increased understanding of molecular mechanism involved in stress response. Here, we review new roles of Hypoxia-inducible factor-1 (HIF-1), one transcription factor regulating stress response-related gene expression: HIF-1 is crucial for invasion and metastasis, independent from its pro-survival function. In addition, HIF-1 mediates pro-metastatic microenvironmental changes of the proteolytic balance as triggered by high systemic levels of tissue inhibitor of metalloproteinases-1 (TIMP-1), typical for many aggressive cancers, and regulates the metabolic switch to glycolysis, notably via activation of the microRNA miR-210. There is preliminary evidence that TIMP-1 also induces miR-210. Such positive-regulatory co-operation of HIF-1α, miR-210, and TIMP-1, all described to correlate with bad prognosis of cancer patients, opens new perspectives of gaining insight into molecular mechanisms of metastasis-inducing evasion of tumor cells from stress.