Human lung-derived mesenchymal stem cell-conditioned medium exerts in vitro antitumor effects in malignant pleural mesothelioma cell lines.

BACKGROUND The soluble factors secreted by mesenchymal stem cells are thought to either support or inhibit tumor growth. Herein, we investigated whether the human lung-derived mesenchymal stem cell-conditioned medium (hlMSC-CM) exerts antitumor activity in malignant pleural mesothelioma cell lines H28, H2052 and Meso4. METHODS hlMSC-CM was collected from the human lung-derived mesenchymal stem cells. Inhibition of tumor cell growth was based on the reduction of cell viability and inhibition of cell proliferation using the XTT and BrdU assays, respectively. Elimination of tumor spheroids was assessed by the anchorage-independent sphere formation assay. The cytokine profile of hlMSC-CM was determined by a chemiluminescence-based cytokine array. RESULTS Our data showed that hlMSC-CM contains a broad range of soluble factors which include: cytokines, chemokines, hormones, growth and angiogenic factors, matrix metalloproteinases, metalloproteinase inhibitors and cell-cell mediator proteins. The 48- and 72-hour hlMSC-CM treatments of H28, H2052 and Meso4 cell lines elicited significant decreases in cell viability and inhibited cell proliferation. The 72-hour hlMSC-CM incubation of H28 cells completely eliminated the drug-resistant sphere-forming cells, which is more potent than twice the half maximal inhibitory concentration of cisplatin. CONCLUSIONS Our findings indicate that the cell-free hlMSC-CM confers in vitro antitumor activities via soluble factors in the tested mesothelioma cells and, hence, may serve as a therapeutic tool to augment the current treatment strategies in malignant pleural mesothelioma.

Active JNK-dependent secretion of Drosophila Tyrosyl-tRNA synthetase by loser cells recruits haemocytes during cell competition

Cell competition is a process by which the slow dividing cells (losers) are recognized and eliminated from growing tissues. Loser cells are extruded from the epithelium and engulfed by the haemocytes, the Drosophila macrophages. However, how macrophages identify the dying loser cells is unclear. Here we show that apoptotic loser cells secrete Tyrosyl-tRNA synthetase (TyrRS), which is best known as a core component of the translational machinery. Secreted TyrRS is cleaved by matrix metalloproteinases generating MiniTyr and EMAP fragments. EMAP acts as a guiding cue for macrophage migration in the Drosophila larvae, as it attracts the haemocytes to the apoptotic loser cells. JNK signalling and Kish, a component of the secretory pathway, are autonomously required for the active secretion of TyrRS by the loser cells. Altogether, this mechanism guarantees effective removal of unfit cells from the growing tissue.

Processing of procollagen III by meprins: new players in extracellular matrix assembly?

Meprins ? and ?, a subgroup of zinc metalloproteinases belonging to the astacin family, are known to cleave components of the extracellular matrix, either during physiological remodeling or in pathological situations. In this study we present a new role for meprins in matrix assembly, namely the proteolytic processing of procollagens. Both meprins ? and ? release the N- and C-propeptides from procollagen III, with such processing events being critical steps in collagen fibril formation. In addition, both meprins cleave procollagen III at exactly the same site as the procollagen C-proteinases, including bone morphogenetic protein-1 (BMP-1) and other members of the tolloid proteinase family. Indeed, cleavage of procollagen III by meprins is more efficient than by BMP-1. In addition, unlike BMP-1, whose activity is stimulated by procollagen C-proteinase enhancer proteins (PCPEs), the activity of meprins on procollagen III is diminished by PCPE-1. Finally, following our earlier observations of meprin expression by human epidermal keratinocytes, meprin ? is also shown to be expressed by human dermal fibroblasts. In the dermis of fibrotic skin (keloids), expression of meprin ? increases and meprin ? begins to be detected. Our study suggests that meprins could be important players in several remodeling processes involving collagen fiber deposition.

Meprins, membrane-bound and secreted astacin metalloproteinases

The astacins are a subfamily of the metzincin superfamily of metalloproteinases. The first to be characterized was the crayfish enzyme astacin. To date more than 200 members of this family have been identified in species ranging from bacteria to humans. Astacins are involved in developmental morphogenesis, matrix assembly, tissue differentiation and digestion. Family members include the procollagen C-proteinase (BMP1, bone morphogenetic protein 1), tolloid and mammalian tolloid-like, HMP (Hydra vulgaris metalloproteinase), sea urchin BP10 (blastula protein) and SPAN (Strongylocentrotus purpuratus astacin), the 'hatching' subfamily comprising alveolin, ovastacin, LCE, HCE ('low' and 'high' choriolytic enzymes), nephrosin (from carp head kidney), UVS.2 from frog, and the meprins. In the human and mouse genomes, there are six astacin family genes (two meprins, three BMP1/tolloid-like, one ovastacin), but in Caenorhabditis elegans there are 40. Meprins are the only astacin proteinases that function on the membrane and extracellularly by virtue of the fact that they can be membrane-bound or secreted. They are unique in their domain structure and covalent subunit dimerization, oligomerization propensities, and expression patterns. They are normally highly regulated at the transcriptional and post-translational levels, localize to specific membranes or extracellular spaces, and can hydrolyse biologically active peptides, cytokines, extracellular matrix (ECM) proteins and cell-surface proteins. The in vivo substrates of meprins are unknown, but the abundant expression of these proteinases in the epithelial cells of the intestine, kidney and skin provide clues to their functions.

Sirolimus ameliorates the enhanced expression of metalloproteinases in a rat model of autosomal dominant polycystic kidney disease

BACKGROUND: Remodelling of matrix and tubular basement membranes (TBM) is a characteristic of polycystic kidney disease. We hypothesized that matrix and TBM degradation by metalloproteinases (MMPs) could promote cyst formation. We therefore investigated the renal expression of MMPs in the Han:SPRD rat model of autosomal dominant polycystic kidney disease (ADPKD) and examined the effect of sirolimus treatment on MMPs. METHODS: 5-week-old male heterozygous (Cy/+) and wild-type normal (+/+) rats were treated with sirolimus (2 mg/kg/day) through drinking water for 3 months. RESULTS: The mRNA and protein levels of MMP-2 and MMP-14 were markedly increased in the kidneys of heterozygous Cy/+ animals compared to wild-type +/+ as shown by RT-PCR and Western blot analyses for MMP-2 and MMP-14, and by zymography for MMP-2. Strong MMP-2 expression was detected by immunoperoxidase staining in cystic epithelial cells that also displayed an altered, thickened TBM. Tissue inhibitor of metalloproteinases-2 (TIMP-2) expression was not changed in Cy/+ kidneys. Sirolimus treatment leads to decreased protein expression of MMP-2 and MMP-14 in Cy/+, whereas MMP-2 and MMP-14 mRNA levels and TIMP-2 protein levels were not affected by sirolimus. CONCLUSION: In summary, in kidneys of the Han:SPRD rat model of ADPKD, there is a marked upregulation of MMP-2 and MMP-14. Sirolimus treatment was associated with a marked improvement of MMP-2 and MMP-14 overexpression, and this correlated also with less matrix and TBM alterations and milder cystic disease.