Procoagulant properties of human MV3 melanoma cells

A correlation between cancer and prothrombotic states has long been described. More recently, a number of studies have focused on the procoagulant mechanisms exhibited by tumor cells. In the present study, we dissected the molecular mechanisms responsible for the procoagulant activity of MV3, a highly aggressive human melanoma cell line. It was observed that tumor cells strongly accelerate plasma coagulation as a result of: i) expression of the blood clotting initiator protein, a tissue factor, as shown by flow cytometry and functional assays (factor Xa formation in the presence of cells and factor VIIa), and ii) direct activation of prothrombin to thrombin by cells, as evidenced by hydrolysis of the synthetic substrate, S-2238, and the natural substrate, fibrinogen. This ability was highly potentiated by the addition of exogenous factor Va, which functions as a co-factor for the enzyme factor Xa. In contrast, prothrombin activation was not observed when cells were previously incubated with DEGR-factor Xa, an inactive derivative of the enzyme. Moreover, a monoclonal antibody against bovine factor Xa reduced the prothrombin-converting activity of tumor cells. In conclusion, the data strongly suggest that MV3 cells recruit factor Xa from the culture medium, triggering an uncommon procoagulant mechanism.

Are the current chronic allograft nephropathy grading systems sufficient to predict renal allograft survival?

A major problem in renal transplantation is identifying a grading system that can predict long-term graft survival. The present study determined the extent to which the two existing grading systems (Banff 97 and chronic allograft damage index, CADI) correlate with each other and with graft loss. A total of 161 transplant patient biopsies with chronic allograft nephropathy (CAN) were studied. The samples were coded and evaluated blindly by two pathologists using the two grading systems. Logistic regression analyses were used to evaluate the best predictor index for renal allograft loss. Patients with higher Banff 97 and CADI scores had higher rates of graft loss. Moreover, these measures also correlated with worse renal function and higher proteinuria levels at the time of CAN diagnosis. Logistic regression analyses showed that the use of angiotensin-converting enzyme inhibitor (ACEI), hepatitis C virus (HCV), tubular atrophy, and the use of mycophenolate mofetil (MMF) were associated with graft loss in the CADI, while the use of ACEI, HCV, moderate interstitial fibrosis and tubular atrophy and the use of MMF were associated in the Banff 97 index. Although Banff 97 and CADI analyze different parameters in different renal compartments, only some isolated parameters correlated with graft loss. This suggests that we need to review the CAN grading systems in order to devise a system that includes all parameters able to predict long-term graft survival, including chronic glomerulopathy, glomerular sclerosis, vascular changes, and severity of chronic interstitial fibrosis and tubular atrophy.

Proximal tubular dysfunction as an indicator of chronic graft dysfunction

New strategies are being devised to limit the impact of renal sclerosis on graft function. Individualization of immunosuppression, specifically the interruption of calcineurin-inhibitors has been tried in order to promote better graft survival once chronic graft dysfunction has been established. However, the long-term impact of these approaches is still not totally clear. Nevertheless, patients at higher risk for tubular atrophy and interstitial fibrosis (TA/IF) development should be carefully monitored for tubular function as well as glomerular performance. Since tubular-interstitial impairment is an early event in TA/IF pathogenesis and associated with graft function, it seems reasonable that strategies directed at assessing tubular structural integrity and function would yield important functional and prognostic data. The measurement of small proteins in urine such as α-1-microglobulin, N-acetyl-beta-D-glucosaminidase, alpha/pi S-glutathione transferases, β-2 microglobulin, and retinol binding protein is associated with proximal tubular cell dysfunction. Therefore, its straightforward assessment could provide a powerful tool in patient monitoring and ongoing clinical assessment of graft function, ultimately helping to facilitate longer patient and graft survival associated with good graft function.

Increased expression of tissue factor and protease-activated receptor-1 does not correlate with thrombosis in human lung adenocarcinoma

A correlation between cancer and hypercoagulability has been described for more than a century. Patients with cancer are at increased risk for thrombotic complications and the clotting initiator protein, tissue factor (TF), is possibly involved in this process. Moreover, TF may promote angiogenesis and tumor growth. In addition to TF, thrombin seems to play a relevant role in tumor biology, mainly through activation of protease-activated receptor-1 (PAR-1). In the present study, we prospectively studied 39 lung adenocarcinoma patients in relation to the tumor expression levels of TF and PAR-1 and their correlation with thrombosis outcome and survival. Immunohistochemical analysis showed TF positivity in 22 patients (56%), most of them in advanced stages (III and IV). Expression of PAR-1 was found in 15 patients (39%), most of them also in advanced stages (III and IV). Remarkably, no correlation was observed between the expression of TF or PAR-1 and risk for thrombosis development. On the other hand, patients who were positive for TF or PAR-1 tended to have decreased long-term survival. We conclude that immunolocalization of either TF or PAR-1 in lung adenocarcinoma may predict a poor prognosis although lacking correlation with thrombosis outcome.

Ischemia preconditioning is neuroprotective in a rat cerebral ischemic injury model through autophagy activation and apoptosis inhibition

Sublethal ischemic preconditioning (IPC) is a powerful inducer of ischemic brain tolerance. However, its underlying mechanisms are still not well understood. In this study, we chose four different IPC paradigms, namely 5 min (5 min duration), 5×5 min (5 min duration, 2 episodes, 15-min interval), 5×5×5 min (5 min duration, 3 episodes, 15-min intervals), and 15 min (15 min duration), and demonstrated that three episodes of 5 min IPC activated autophagy to the greatest extent 24 h after IPC, as evidenced by Beclin expression and LC3-I/II conversion. Autophagic activation was mediated by the tuberous sclerosis type 1 (TSC1)-mTor signal pathway as IPC increased TSC1 but decreased mTor phosphorylation. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and hematoxylin and eosin staining confirmed that IPC protected against cerebral ischemic/reperfusion (I/R) injury. Critically, 3-methyladenine, an inhibitor of autophagy, abolished the neuroprotection of IPC and, by contrast, rapamycin, an autophagy inducer, potentiated it. Cleaved caspase-3 expression, neurological scores, and infarct volume in different groups further confirmed the protection of IPC against I/R injury. Taken together, our data indicate that autophagy activation might underlie the protection of IPC against ischemic injury by inhibiting apoptosis.