Conventional immunosuppressive drugs have been used effectively to prevent immunologic rejection in organ transplantation. Individuals taking these drugs are at risk, however, for the development and recurrence of cancer. In the present study we show that the new immunosuppressive drug rapamycin (RAPA) may reduce the risk of cancer development while simultaneously providing effective immunosuppression. Experimentally, RAPA inhibited metastatic tumor growth and angiogenesis in in vivo mouse models. In addition, normal immunosuppressive doses of RAPA effectively controlled the growth of established tumors. In contrast, the most widely recognized immunosuppressive drug, cyclosporine, promoted tumor growth. From a mechanistic perspective, RAPA showed antiangiogenic activities linked to a decrease in production of vascular endothelial growth factor (VEGF) and to a markedly inhibited response of vascular endothelial cells to stimulation by VEGF. Thus, the use of RAPA, instead of cyclosporine, may reduce the chance of recurrent or de novo cancer in high-risk transplant patients.

Cancer is an increasingly recognized problem associated with immunosuppression. Recent reports, however, suggest that the immunosuppressive agent rapamycin has anti-cancer properties that could address this problem. Thus far, rapamycin's effects on immunity and cancer have been studied separately. Here we tested the effects of rapamycin, versus cyclosporine A (CsA), on established tumors in mice simultaneously bearing a heart allograft. In one tumor-transplant model, BALB/c mice received subcutaneous syngenic CT26 colon adenocarcinoma cells 7 days before C3H ear-heart transplantation. Rapamycin or CsA treatment was initiated with transplantation. In a second model system, a B16 melanoma was established in C57BL/6 mice that received a primary vascularized C3H heart allograft. In vitro angiogenic effects of rapamycin and CsA were tested in an aortic ring assay. Results show that CT26 tumors grew for 2 weeks before tumor complications occurred. However, rapamycin protected allografts, inhibited tumor growth, and permitted animal survival. In contrast, CsA-treated mice succumbed to advancing tumors, albeit with a functioning allograft. Rapamycin's antitumor effect also functioned in severe combined immunodeficient BALB/c mice. Similar effects of the drugs occurred with B16 melanomas and primary vascularized C3H allografts in C57BL/6 mice. Furthermore, in this model, rapamycin inhibited the tumor growth-enhancing effects of CsA. Moreover, in vitro experiments showed that CsA promotes angiogenesis by a transforming growth factor-beta-related mechanism, and that this effect is abrogated by rapamycin. This study demonstrates that rapamycin simultaneously protects allografts from rejection and attacks tumors in a complex transplant-tumor situation. Notably, CsA protects allografts from rejection, but cancer progression is promoted in transplant recipients.

We report two cases of proximal endograft collapse with an almost complete aortic occlusion after endovascular tube-graft treatment of thoracic aortic disease (thoracic aneurysm after a type B dissection, traumatic blunt aortic rupture) using the TAG Gore system. Oversizing of endografts is known to cause this complication. In our two cases, however, the oversizing was between 12% and 21.7%, which is less than the allowed oversizing of 25% that is recommended by the manufacturer. This endograft-related complication might be due to a poor alignment of the currently available endografts in highly angulated and tight aortic arches. In the first case, a combined endovascular and open emergent repair procedure achieved a reopening of the proximal endograft by proximal extension (TAG Gore). In the second case, proximal extension was not considered owing to a precise positioning of the endograft distal to the left carotid artery. A balloon-expanding Palmaz stent was therefore placed interventionally in the proximal part of the TAG graft to expand the endograft and to avoid another collapse of the device. This proximal endograft collapse has to be acknowledged as a potentially hazardous complication. We therefore recommend that the proximal part of thoracic endografts in the aortic arch should be closely monitored and we offer two possible endovascular solutions for resolving the problem of proximal endograft collapse.

The long-term results of this prospective, randomized, single-center study revealed a high incidence of relevant restenosis and neurologic symptoms after CAS. CEA seems to be superior to CAS concerning the development of restenosis and significant prevention of stroke. However, the long-term results of the ongoing multicenter trials have to be awaited for a final conclusion.

Purpose: Despite current chemotherapies, pancreatic cancer remains an uncontrollable, rapidly progressive disease. Here, we tested an approach combining a recently described antiangiogenic drug, rapamycin, with standard gemcitabine cytotoxic therapy on human pancreatic tumor growth.Experimental Design: Tumor growth was assessed in rapamycin and gemcitabine-treated nude mice orthotopically injected with metastatic L3.6pl human pancreatic cancer cells. H&E staining was performed on tumors, along with Ki67 staining for cell proliferation and immunohistochemical terminal deoxynucleotidyl transferase-mediated nick end labeling and CD31 analysis. Rapamycin-treated tumor vessels were also directly examined in dorsal skin-fold chambers for blood flow after thrombosis induction. Cell death in human umbilical vein endothelial cells was assessed by flow cytometry after annexin-V staining.Results: Rapamycin therapy alone inhibited tumor growth and metastasis more than gemcitabine, with remarkable long-term tumor control when the drugs were combined. Mechanistically, H&E analysis revealed tumor vessel endothelium damage and thrombosis with rapamycin treatment. Indeed, dorsal skin-fold chamber analysis of rapamycin-treated tumors showed an increased susceptibility of tumor-specific vessels to thrombosis. Furthermore, terminal deoxynucleotidyl transferase-mediated nick end labeling/ CD31 double staining of orthotopic tumors demonstrated apoptotic endothelial cells with rapamycin treatment, which also occurred with human umbilical vein endothelial cells in vitro. In contrast, gemcitabine was not antiangiogenic and, despite its known cytotoxicity, did not reduce proliferation in orthotopic tumors; nevertheless, rapamycin did reduce tumor proliferation.Conclusions: Our data suggest a novel mechanism whereby rapamycin targets pancreatic tumor endothelium for destruction and thrombosis. We propose that rapamycin-based vascular targeting not only reduces tumor vascularization, it decreases the number of proliferating tumor cells to be destroyed by gemcitabine, thus introducing a new, clinically feasible strategy against pancreatic cancer.

Rhodamine 6G is a vital dye accumulating in the mitochondria of cells. It is used in intravital fluorescence microscopy for contrast enhancement of white blood cells (WBC), enabling visualization of WBC in the microvasculature even at high center flow velocity. The aim of this study was to examine the kinetics of WBC staining after intravascular administration of rhodamine 6G in Lewis rats, Syrian golden hamsters and BALB/c mice. For this purpose, WBC were isolated from whole blood and the percentage of cells stained positively as well as their fluorescence intensity were measured by flow cytometry 5, 15, 30 and 60 min after dye administration. Injection of 0.06-0.2 mg/kg body weight of rhodamine 6G resulted in staining of practically all granulocytes and monocytes over the entire observation period of 60 min. Fluorescence intensity of WBC was adequate to be detected in an experimental setup for intravital fluorescence microscopy in the hamster dorsal skinfold chamber. The degree of WBC staining was different in the species studied, yielding a higher percentage of stained lymphocytes in rats than in mice and hamsters. Staining of lymphocytes declined within 60 min after rhodamine application, the loss of fluorescent label being most pronounced in hamster cells. After 15-30 min, relative fluorescence intensity of stained lymphocytes had decreased considerably, indicating the need for reinjection of the dye or limiting microscopic analysis to approximately 15 min after rhodamine 6G administration. While the intravascular injection of rhodamine 6G results in adequate staining of granulocytes and monocytes, only a fraction of lymphoid cells are stained.

CAS patients with untreated asymptomatic > 70% restenosis had an extremely low rate of late ipsilateral stroke (0.8% over 50 months). CEA patients with untreated, asymptomatic > 70% restenosis had a significantly higher risk of late ipsilateral stroke (compared with patients with no restenosis), but this was only 5% at 37 months. Overall, 97% of all late ipsilateral strokes after CAS and 85% after CEA occurred in patients without evidence of significant restenosis or occlusion.

Functional capillary density (FCD) is one of the parameters obtained by intravital microscopy using epi-illumination of the tissue surface or trans-illumination of thin tissue layers. FCD, defined as the length of red cell-perfused capillaries per observation area (cm^-1), has been used as an indicator of the quality of tissue perfusion in various animal models. Quantitative analysis of FCD in randomly selected regions of the tissue is performed by means of a computer-assisted video analysis system which allows calculation of the length of RBC-perfused capillaries. Basically, two different mathematical approaches can be employed: the first approach is based on the addition of the distances between two neighboring points (pixels) on the video screen (Pythagorean principle). The second approach uses the superimposition of a grid system that allows estimation of the capillary length by counting the number of intersections between the capillaries and the grid lines (stereological approach). The immanent error has been calculated in our laboratory to be ± 1 % with the Pythagorean and ± 5% with the stereological method. Beside these systematic errors of computerized measurement, the individual (user-dependent) errors occurring during recognition and redrawing of the capillaries on the video image with use of a digitizing tablet are in the range of ± 10% (intraindividual) and ± 70% (interindividual) for the recognition and ± 3% (interindividual) for the redrawing procedure. Our studies indicate that the errors resulting from the use of a computer-assisted calculation (Pythagorean or stereological approach) or the user-assisted redrawing of the capillaries are negligible when compared to the errors made during recognition of the capillaries on the video screen. The methods are applied for assessment of FCD in two different microcirculation models of skin muscle and pancreas yielding highly reproducible, user-independent results under physiologic conditions and the pathophysiologic conditions of ischemia-reperfusion.