Purpose: The anaphylatoxin C5a is a chemoattractant that induces leukocyte migration via C5a receptor (C5aR). There is emerging evidence that C5a is generated in the cancer microenvironment. We therefore sought C5aR expression and a direct influence of the C5a-C5aR axis on cancer cells.Experimental Design: C5aR expression was investigated in human cancer tissues and cell lines. Effects of C5a stimulation on cancer cells were studied by cytoskeletal rearrangement, time-lapse analysis, Matrigel chamber assay, and invasion in nude mouse in a comparison of C5aR-expressing cancer cells with control cells.Results: C5aR was aberrantly expressed in various human cancers. Several cancer cell lines also expressed C5aR. C5a triggered cytoskeletal rearrangement and enhanced cell motility three-fold and invasiveness 13-fold of C5aR-expressing cancer cells. Such enhancement by C5a was not observed in control cells. Cancer cell invasion was still enhanced in the absence of C5a concentration gradient and even after the removal of C5a stimulation, suggesting that random cell locomotion plays an important role in C5a-triggered cancer cell invasion. C5a increased the release of matrix metalloproteinases (MMP) from cancer cells by two-to 11-fold, and inhibition of MMP activity abolished the C5a-enhancing effect on cancer cell invasion. Compared with control cells, C5aR-expressing cells spread 1.8-fold more broadly at implanted nude mouse skin sites only when stimulated with C5a.Conclusions: These results illustrate a novel activity of the C5a-C5aR axis that promotes cancer cell invasion through motility activation and MMP release. Targeting this signaling pathway may provide a useful therapeutic option for cancer treatment.

No abstract

Staphylococcus aureus is the most frequently isolated pathogen in Gram-positive sepsis often complicated by a blood clotting disorder, and is the leading cause of infective endocarditis induced by bacterial destruction of endocardial tissues. The bacterium secretes cysteine proteases referred to as staphopain A (ScpA) and staphopain B (SspB). To investigate virulence activities of staphopains pertinent to clotting disorders and tissue destruction, we examined their effects on collagen, one of the major tissue components, and on plasma clotting. Both staphopains prolonged the partial thromboplastin time of plasma in a dose-and activitydependent manner, with SspB being threefold more potent than ScpA. Staphopains also prolonged the thrombin time of both plasma and fibrinogen, indicating that these enzymes can cause impaired plasma clotting through fibrinogen degradation. Whereas SspB cleaved the fibrinogen Aa-chain at the C-terminal region very efficiently, ScpA degraded it rather slowly. This explains the superior ability of the former enzyme to impair fibrinogen clottability. Enzymically active staphopains, at concentrations as low as 10 nM, degraded collagen with comparable efficiency. These results show novel virulence activities of staphopains in degrading fibrinogen and collagen, and suggest an involvement of staphopains in the clotting impairment and tissue destruction caused by staphylococcal infection. INTRODUCTIONSepsis is a serious medical condition, in which living bacteria are present in the bloodstream. Shock and disseminated intravascular coagulation (DIC) are common and potentially fatal consequences of sepsis. DIC occurs in as many as 40 % of sepsis patients, often leading to multiple organ failure (Levi & ten Cate, 1999), and is directly linked to a high mortality rate. Clinical studies have shown that Gram-positive micro-organisms are as common as Gram-negative bacteria in causing sepsis (Ahmed et al., 1991;Kieft et al., 1993).Staphylococcus aureus is the most frequently isolated pathogen in Gram-positive sepsis (Ahmed et al., 1991;Bone, 1993). In addition, this bacterium is the leading cause of infective endocarditis in many regions of the world (Fowler et al., 2005). The development of endocarditis increases the mortality rate of patients with bacteraemia (Chang et al., 2003) et al., 2005). These findings suggest that staphopains contribute to S. aureus septic shock, one of the major fatal complications of sepsis.Clotting induction and a subsequent tendency to bleeding are prominent clinical features of DIC, another lethal outcome of sepsis. Staphopains may participate in the onset of the clotting disorder through activation or inactivation of clotting factors in plasma by proteolytic cleavage. However, the ability of staphopains to affect plasma clotting has not been studied. Invasion of S. aureus into the endocardium to cause infective endocarditis requires the degradation of connective tissue including extracellular matrix proteins, and is facilitated by proteases. In this context, staphy...