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.