Tumor Microcirculation Research Articles

Changes of tumor microcirculation after transcatheter arterial chemoembolization: first pass perfusion MR imaging and Chinese ink casting in a rabbit model.

To observe the change of tumor microcirculation after transcatheter arterial chemoembolization (TACE) with bletilla microspheres by using first pass perfusion MR imaging (FP) and Chinese ink casting. VX2 carcinoma cells were surgically implanted into the left and right lobes of liver of 30 New Zealand white rabbits, which were divided into 3 groups at random. Emulsion of lipiodol mixed with mitomycin C, and 5-FU bletilla microspheres were injected into the hepatic artery respectively, and saline was used as control agent. MR imaging was performed with turbo-flash sequence 14 d after tumor implantation and 7 d after interventional therapy. The steepest slopes (SS) of the signal intensity versus time curves were created for quantitative analysis, 7.5% Chinese ink gelatin solution was injected through ascending artery (17 cases) or portal vein (2 cases) for lesion microvessel area (MVA) measurement after the last MRI examination. The correlation between perfusion imaging and MVA was studied blindly. The SS values at the rim of tumor in lipiodol group (mean, 49% per second) and bletilla group (mean, 35% per second) were significantly decreased (P<0.05) as compared with control group (mean, 124% per second), no difference was found between lipiodol and bletilla groups (P>0.05). In lipiodol group, the MVAs (24 974+/-11 836 microm(2)) in the center of the tumor were significantly smaller than those of the control group (35 510+/-15 675 microm(2)) (P<0.05), while the MVAs (80 031+/-22 745 microm(2)) around the tumor were significantly increased because small and dense plexuses appeared around the tumor which correlated to intense reaction of granulation tissue. None of the vessels was seen in the tumor in bletilla group, the peripheral MVAs of the tumor were significantly smaller than those of the control group (P<0.05) and lipiodol group (P<0.05). There was a good correlation between SS and MVAs in control group (r(s), 0.985, P<0.0001) and bletilla group (r(s), 0.743, P<0.05), the correlation was not significant in lipiodol group (r(s), 0.527, P>0.05). TACE with bletilla microspheres may enhance its anti-tumor effect by inhibiting the angiogenesis, and FP-MRI provides useful information to assess the TACE effect by depicting tumor vascularization and perfusion.

Differential relationship between changes in tumour size and microcirculatory functions induced by therapy with an antivascular drug and with cytotoxic drugs: implications for the evaluation of therapeutic efficacy of AC7700 (AVE8062)

A novel combretastatin A-4 derivative, AC7700, which is now in Phase I clinical trials under a new code, AVE8062, has shown strong antitumour effects against solid tumours in rodents because of its powerful and continued stanching of the tumour blood flow (TBF). Despite the strong tumour-suppressing qualities of AC7700, it does not produce an immediate reduction in tumour size. To elucidate the reason for this effect, we investigated the relationship between the change in tumour size in Sato lung carcinoma (SLC) and circulatory functions after therapy with AC7700, doxorubicin (Adriamycin [ADR]), or mitomycin C (MMC). To measure time-lapse changes in TBF with the hydrogen clearance method at the same site after drug administration, we developed a new apparatus for keeping electrodes within a tumour. AC7700 led to the destruction of both cancer cells and tumour vessels by interrupting the supply of nutrients. Intravenous (i.v.) administration of fluorescent dyes after AC7700 treatment revealed no fluorescence within the tumour vessels, which confirmed that the tumour microcirculation had been completely blocked. In contrast, ADR led to the destruction of SLC tumour cells, but did not have the same effect on tumour vessels. Intravenously administered fluorescent dyes immediately reached the tumour, which indicated that the tumour vasculature remained intact, and the TBF remained at the preadministration level, even 6 days after ADR treatment. In addition, although the size of the tumour increased slightly for 2 days with ADR treatment, possibly because of swelling of the cancer cells, thereafter it continued to decrease. MMC had virtually no effect on SLC tumour cells, tumour size or tumour vessels. We conclude that changes in tumour size brought about by cancer chemotherapy depend not only on the sensitivity of the cancer cells to the drug in question, but also on the nature of changes in the microcirculatory functions of the tumour brought about by the therapy. When both tumour cells and the tumour vasculature are destroyed, the effectiveness of therapy can not be determined from changes in tumour size alone.

Insights into the mechanisms of lymph node metastasis.

The mechanisms by which malignant tumors leave the primary tumor site, invade lymphatics, and metastasize to regional lymph nodes (RLNs) are complex and interrelated. Although the phenomenon of lymph node metastasis has been recognized for over 200 years, the exact mechanisms have only recently been the subject of intense interest and sophisticated experimentation. Sentinel lymph node biopsy has rapidly entered the clinical mainstream for melanoma and breast carcinoma, and this technique has provided confirmation of the orderly anatomic progression of tumor cells from primary site to the RLNs through lymphatic capillaries and trunks. Exciting studies involving the pathophysiology of interstitial fluid pressure in tumors and the peritumoral extracellular matrix have focused on lymphatic flow and tumor microenvironment and microcirculation. Molecular techniques have led to the definition of unique markers found on lymphatic endothelial cells. These markers have enabled scientists to identify peritumoral and intratumoral lymphatics and to visualize the ingrowth of tumor cells into the lumena of lymphatic capillaries. Tumor-secreted cytokines, such as vascular endothelial growth factors (VEGF)-C and -D, bind to VEGF receptors on lymphatic endothelial cells and induce proliferation and growth of new lymphatic capillaries; this process is similar to the well-known mechanism of angiogenesis, which results from the proliferation of new blood vessel capillaries. Lymphangiogenesis is associated with an increased incidence of RLN metastasis, and it is possible that this step is essential to the metastatic process. Directional movement toward lymphatics and lymph nodes appears to follow a chemokine gradient, and it is likely that some tumor cells that express certain types of chemokine receptors are more likely to metastasize to the RLNs. In contrast, tumor cells that do not express specific receptors that are responsive to lymphatic chemokines may not metastasize. New knowledge regarding the molecules involved in these processes should enable improvements in prognostic and possibly therapeutic approaches to the management of malignant tumors.

Imaging tumor angiogenesis with contrast ultrasound and microbubbles targeted to alpha(v)beta3.

Angiogenesis is a critical determinant of tumor growth and metastasis. We hypothesized that contrast-enhanced ultrasound (CEU) with microbubbles targeted to alpha(v)-integrins expressed on the neovascular endothelium could be used to image angiogenesis. Malignant gliomas were produced in 14 athymic rats by intracerebral implantation of U87MG human glioma cells. On day 14 or day 28 after implantation, CEU was performed with microbubbles targeted to alpha(v)beta3 by surface conjugation of echistatin. CEU perfusion imaging with nontargeted microbubbles was used to derive tumor microvascular blood volume and blood velocity. Vascular alpha(v)-integrin expression was assessed by immunohistochemistry, and microbubble adhesion was characterized by confocal microscopy. Mean tumor size increased markedly from 14 to 28 days (2+/-1 versus 35+/-14 mm2, P<0.001). Tumor blood volume increased by approximately 35% from day 14 to day 28, whereas microvascular blood velocity decreased, especially at the central portions of the tumors. On confocal microscopy, alpha(v)beta3-targeted but not control microbubbles were retained preferentially within the tumor microcirculation. CEU signal from alpha(v)beta3-targeted microbubbles in tumors increased significantly from 14 to 28 days (1.7+/-0.4 versus 3.3+/-1.0 relative units, P<0.05). CEU signal from alpha(v)beta3-targeted microbubbles was greatest at the periphery of tumors, where alpha(v)-integrin expression was most prominent, and correlated well with tumor microvascular blood volume (r=0.86). CEU with microbubbles targeted to alpha(v)beta3 can noninvasively detect early tumor angiogenesis. This technique, when coupled with changes in blood volume and velocity, may provide insights into the biology of tumor angiogenesis and be used for diagnostic applications.

Tumor microcirculation and diffusion predict therapy outcome for primary rectal carcinoma

Purpose The aim of our study was to correlate perfusion indices and apparent diffusion coefficients with therapy outcome after chemoradiation. Methods and materials In 34 patients with primary rectal carcinoma (cT3) undergoing preoperative chemoradiation, pretherapeutic perfusion indices and apparent diffusion coefficients were obtained by dynamic or diffusion-weighted magnetic resonance imaging. Therapy response was defined if the pathologic observation revealed no invasion into the perirectal fat after chemoradiation. Results In 18 patients, a response and in 16, no response was observed. Statistically significant differences were found for the mean perfusion index ( p < 0.001; 7.5 ± 1.5 mL/min/100 g vs. 10.7 ± 2.7 mL/min/100 g) and for the intratumoral cumulative fraction of pixels with perfusion-indices > 12 mL/min/100 g ( p < 0.001, 3.7 ± 4.0% vs. 24.7 ± 17.9%). A three-way ANOVA resulted in significant effects for therapy responder/nonresponder ( p < 0.001) and for apparent diffusion coefficient and the individual patients. Conclusion Perfusion indices and apparent diffusion coefficients inside the tumor region seem to be of predictive value for therapy outcome of preoperative therapy in patients with primary rectal carcinoma. Higher parameter levels in the nonresponding group could be explained by increased shunt flow or increased angiogenic activity in aggressive tumor cell clusters resulting in reduced nutrients supply and higher fraction of intratumoral necrosis respectively.

Platelet-endothelial interaction in tumor angiogenesis and microcirculation

Activated platelets release angiogenic growth factors and have therefore been proposed to contribute to tumor angiogenesis within a potentially prothrombotic tumor microcirculation. The aim of the study was to investigate interactions of platelets with the angiogenic microvascular endothelium of highly vascularized solid tumors during growth and in response to endothelial stimulation in comparison with normal subcutaneous tissue. Experiments were performed in the dorsal skinfold chamber preparation of C57BL/6J mice bearing the Lewis lung carcinoma (LLC-1) or methylcholanthrene-induced fibrosarcoma (BFS-1). Fluorescently labeled rolling and adherent platelets, red blood cell velocity, and vessel diameters were assessed by intravital fluorescence microscopy on days 1, 3, 8, and 14 after tumor cell implantation. Slightly elevated numbers of rolling platelets were observed in the early stages of tumor angiogenesis at day 1 (control, 1.7 +/- 0.6; LLC-1, 3.4 +/- 1.8; BFS-1, 3.0 +/- 0.7 [1/mm/s], P <.05) and day 3 (control, 1.6 +/- 0.6; LLC-1, 4.1 +/- 1.7, P <.05; BFS-1, 2.3 +/- 0.5 [1/mm/s]) after tumor cell implantation. Endothelial stimulation with calcium ionophore A23187 at day 14 after tumor cell implantation resulted in a minor increase to 2.1 +/- 0.4 (LLC-1) and 1.8 +/- 0.8 (BFS-1) rolling platelets (1/mm/s) in tumor microvessels compared with 4.9 +/- 0.9 in controls (P <.05). Platelet adherence was not observed. We therefore conclude that in the 2 experimental tumors under study, (1) slightly increased platelet rolling is a transient phenomenon after tumor cell implantation, and (2) platelet-endothelial interaction in response to endothelial stimulation is reduced in tumor microvessels.

Leukocyte behavior in angiogenic vessels is affected by tumor-derived nitric oxide.

Recent studies indicate a possible role of nitric oxide (NO) in regulating leukocyte-endothelial cell interactions, which plays a key role in the tumor immunity. The purpose of the present study is aimed to observe the tumor hemodynamics intravitally and to clarify the effect of NO on tumor microcirculation by means of a real-time confocal laser-scanning microscope using NO-reactive indicators. Visualization of localization of NO and the leukocyte behavior was made in the mesenteric microvessels of an experimental tumor model rat. Production of NO was clearly visualized along the endothelium of the tumor-free rats, but scarcely found in the newly formed tumor microvessels. A higher level of NO production was observed in a solid tumor region, where a more marked decrease in the leukocyte-endothelial cell interactions was observed. Local administration of a NO synthase (NOS) inhibitor increased leukocyte adhesion. This indicates that tumor-derived NOS creates the tumor specific microenvironment of the immature angiogenic tumor vessels, thereby modulating leukocyte behavior.

High-frequency 3-D color-flow imaging of the microcirculation

High-frequency (> 20 MHz) ultrasound (US) flow imaging has the potential to be an important tool for assessing microvascular blood flow in superficial tissues noninvasively. In this paper, we describe the development and evaluation of a 3-D US flow imaging system capable of operating at center frequencies in the 20- to 50-MHz range. Flow images are made for tissue volumes of sizes up to 10 mm laterally and 5 mm in depth, permitting a range of scientific and clinical applications. To acquire data sets in a reasonable time, the 2-D sections were derived from data collected with a transducer that was scanning continuously in a direction perpendicular to the beam axis. Due to spectral broadening effects induced by scanning tissue, significant tradeoffs must be made between frame rate, lateral resolution and the minimum detectable blood velocity. 3-D flow images were reconstructed with flow data acquired from a series of adjacent planes. The system was evaluated at a center frequency of 50 MHz, using two PVDF transducers with lateral resolutions of 43 μm and 65 μm and axial resolutions of 66 μm to 72 μm, respectively. Velocity ranges were from below 1 mm/s to 25 mm/s. In vivo validation experiments using the mouse ear demonstrated the ability to follow branching patterns of closely spaced microvessels from 30 μm to 100 μm in diameter. Experiments conducted on mouse tumors successfully imaged microvessel morphology in the tumor microcirculation. (E-mail: goetzda@sten.sunnybrook.utoronto.ca)

Complex microcirculation patterns detected by confocal indocyanine green angiography predict time to growth of small choroidal melanocytic tumors: MuSIC Report II

Purpose Multiple independent laboratories have confirmed the histologic observation that some tumor microcirculation patterns (MCPs) in uveal melanomas are associated strongly with death resulting from metastatic disease. Because these patterns are imageable with confocal indocyanine green angiography (ICG), we designed a prospective study to evaluate whether these angiographically detectable MCPs predict time to tumor growth. Design Observational case series, prospective, non-randomized. Participants Ninety-eight patients with unilateral, small, choroidal melanocytic tumors. Methods The following information and tumor characteristics were recorded for each patient: demographic parameters, best-corrected visual acuity, intraocular pressure, related visual symptoms, location and dimension of tumor, pigmentation, orange pigment, drusen, tumor-associated hemorrhage, subretinal fluid, and confocal ICG angiographically determined microcirculation patterns—silent (avascularity), normal (preexisting normal choroidal vessels within the tumor), straight vessels, parallel without and with cross-linking, arcs without and with branching, loops, and networks. Main outcome measures Time to growth of the tumor, with growth defined as an increase in the maximal apical tumor height of 0.5 mm measured by standardized A-scan ultrasonography, photographic documentation of an increase of the largest basal diameter of at least 1.5 mm, advancement of one tumor border of at least 0.75 mm, or a combination thereof. Results Twenty-eight of the 98 tumors in this study (29%) met the predetermined criteria for tumor growth. The median time to growth was 127 days (range, 51–625 days). The following tumor characteristics were significantly associated with time to tumor growth: flashes ( P = 0.0224), orange pigment ( P = 0.012), subretinal fluid ( P < 0.001), maximum basal tumor diameter at initial examination ( P = 0.015), maximum apical tumor height ( P < 0.001), parallel with cross-linking MCP ( P < 0.001), arcs with branching MCP ( P = 0.006), loops ( P < 0.001), and networks ( P < 0.001). Of these, the angiographic documentation of any of the complex MCPs (parallel with cross-linking, arcs with branching, loops, networks, or a combination thereof) showed the strongest association with the time to tumor growth in a Cox proportional hazard model. Conclusions The characteristics of our patient cohort are comparable by clinical and echographic parameters with cohorts for predicting tumor growth, described previously in the literature. In addition, we detected a novel clinical predictor of tumor growth: the confocal ICG angiographic detection of complex MCPs.

Nifedipine improves blood flow and oxygen supply, but not steady-state oxygenation of tumours in perfusion pressure-controlled isolated limb perfusion.

Isolated limb perfusion allows the direct application of therapeutic agents to a tumour-bearing extremity. The present study investigated whether the dihydropyridine-type Ca2+-channel blocker nifedipine could improve blood flow and oxygenation status of experimental tumours during isolated limb perfusion. Perfusion was performed by cannulation of the femoral artery and vein in rats bearing DS-sarcoma on the hind foot dorsum. Perfusion rate was adjusted to maintain a perfusion pressure of 100–140 mmHg throughout the experiment. Following equilibration, nifedipine was continuously infused for 30 min (8.3 μg min−1 kg−1 BW). During constant-pressure isolated limb perfusion, nifedipine can significantly increase perfusion rate (+100%) and RBC flux (+60%) through experimental leg tumours. ‘Steal phenomena’ in favour of the surrounding normal tissue and oedema formation were not observed. Despite the increased oxygen availability (+63%) seen upon application of this calcium channel blocker, nifedipine does not result in a substantial reduction of tumour hypoxia, most probably due to an increase in O2 uptake with rising O2 supply to the tumour-bearing hind limb. Nifedipine application during isolated limb perfusion can enhance tumour microcirculation and may therefore promote the delivery (pharmacokinetics) of anti-cancer drugs to the tumour and by this improve the efficacy of pressure-controlled isolated limb perfusion.British Journal of Cancer (2002) 87, 1462–1469. doi:10.1038/sj.bjc.6600611 www.bjcancer.com© 2002 Cancer Research UK

Tumor microcirculation and diffusion predicts therapy outcome for primary rectal carcinoma undergoing combined chemoradiation

Tumor microcirculation and diffusion predicts therapy outcome for primary rectal carcinoma undergoing combined chemoradiation

Development of an arterial tree in C6 gliomas but not in A375 melanomas.

The microcirculation of tumors is severely disturbed. Tumors are usually supplied by fragile capillaries and do not possess the natural hierarchy of blood vessels. The detection of specific markers for arterial and venous endothelial cells (ECs) now enables us to study the vascular tree in tumors. We have injected rat C6 glioma and human A375 melanoma cells into 3.5- to 4-day-old avian embryos. After 10-12 days of reincubation the tumor cells formed solid tumors vascularized by host ECs. In contrast to the melanomas, the gliomas induced an almost normal vascular tree with arterial and venous vessels. The arterial vessels express the arterial EC marker ephrin-B2, and possess a media of smooth muscle alpha-actin (alphaSMA)-positive cells. Venular vessels in the gliomas are ephrin-B2-negative/alphaSMA-positive. Although the gliomas may represent a rare case of vascular tree induction in tumors, the results underline the heterogeneity of tumor-induced angiogenesis. This has an impact on tumor blood flow and thereby also on the efficacy of chemotherapy and radiotherapy.

Tumour oxygenation measurements using computed tomography and magnetic resonance imaging

Tumour oxygenation measurements using computed tomography and magnetic resonance imaging

Pancreas Microenvironment Promotes VEGF Expression and Tumor Growth: Novel Window Models for Pancreatic Tumor Angiogenesis and Microcirculation

Pancreatic cancer has a poor prognosis, and treatment strategies based on preclinical research have not succeeded in significantly extending patient survival. This failure likely stems from the general lack of information on pancreatic tumor physiology, attributable to the difficulties in developing relevant, orthotopic models that accurately reflect pancreatic cancer in the clinic. To overcome this limitation, we developed abdominal wall windows suitable for intravital microscopy that allowed us to monitor angiogenesis and microvascular function noninvasively during tumor growth in vivo. We used two complementary tumor models in mice: orthotopic (human ductal pancreatic adenocarcinoma, PANC-1, grown in the pancreas), and ectopic (PANC-1 grown in the abdominal wall). We found that orthotopic PANC-1 tumors grew faster than the ectopic tumors and exhibited metastatic spread in the late stage similar to advanced pancreatic cancer in the clinic. Orthotopic PANC-1 tumors expressed vascular endothelial growth factor (VEGF)121 and VEGF165, contained higher levels of tumor cell–derived VEGF protein, and maintained vascular density and hyperpermeability during exponential tumor growth. Orthotopic PANC-1 tumors showed lower leukocyte–endothelial interactions in the early stage of growth. In addition, both VEGF121 and VEGF165 promoted the growth of PANC-1 cells in vitro. Finally, Anti-VEGF neutralizing antibody inhibited angiogenesis and tumor growth of PANC-1 tumors in both sites. We conclude that the orthotopic pancreas microenvironment enhances VEGF expression, which stimulates growth of PANC-1 tumors (compared with ectopic tumors). The mechanism is autocrine and/or paracrine and also is involved in the maintenance of blood vessels. This comparative system of orthotopic and ectopic pancreatic cancer will provide the rigorous understanding of pancreatic tumor pathophysiology needed for development of novel therapeutic strategies.

Improved response of colon cancer xenografts to radioimmunotherapy with pentoxifylline treatment.

A methylxanthine, pentoxifylline (PTX), has the potential to improve tumour microcirculation and oxygenation in vivo. We aimed to determine whether this agent would enhance the response of tumours to experimental radioimmunotherapy (RIT). Balb/c nu/nu mice with xenografts of LS180 human colon cancer were treated with 4.63 MBq of 131I-A7 anti-colorectal monoclonal antibody. A dose of 50 mg/kg of PTX was administered i.p. immediately after the 131I-A7 injection and daily thereafter for 7 days. The effect of PTX administration on 131I-A7 targeting in tumours was assessed with biodistribution and radioluminography on day 2. Intratumoural pO2 was measured with microelectrodes. The administration of PTX alone did not suppress tumour growth, but the efficacy of RIT with 131I-A7 was significantly improved by PTX: tumour volumes on day 15, relative to the initial volume, were 16.8+/-3.60 in the nontreated controls, 13.9+/-2.17 with PTX, 3.43+/-0.44 with RIT, and 1.86+/-0.59 with RIT+PTX (P<0.05). PTX administration did not alter the biodistribution or intratumoural distribution of 131I-A7. However, intratumoural pO2 was significantly improved by PTX administration: 16.9+/-9.75 mmHg in control tumours versus 25.6+/-11.3 mmHg in PTX-treated tumours (P<0.01). These results indicate that PTX-induced radiosensitisation of tumour cells due to better oxygenation is responsible for the better RIT outcomes, because the net radiation absorbed dose to the tumours did not appear to be changed.

Developments in ultrasound contrast media.

Ultrasound microbubble contrast agents are effective and safe echo enhancers. An ingenious array of methods are employed to achieve stability and provide a clinically useful enhancement period. Microbubbles enhance ultrasound signals by up to 25 dB (greater than 300-fold increase) due to resonant behaviour. This is used to rescue failed Doppler studies and may be extended to image the microcirculation of tumours and the myocardium using non-linear modes. Functional studies open up a whole range of applications by using a variety of active and passive quantitation techniques to derive indices from the transit of contrast through a tissue of interest. This has been especially successful in the detection of liver metastases and cirrhosis and shows great promise as a clinical tool. It also has great potential in measuring microcirculatory flow velocity. The demonstration that some microbubbles are not just pure blood pool agents but have a hepatosplenic specific phase has extended the versatility of ultrasound. Imaging of this stationary phase with non-linear modes such as phase inversion and stimulated acoustic emission, has improved the sensitivity and specificity of ultrasound in the detection and characterisation of focal liver lesions to rival that of CT and MR.

Imaging the microcirculation of untreated and treated human choroidal melanomas.

Histologically demonstrable microcirculation patterns (microcirculation pattern) of human choroidal melanomas have prognostic significance for the patient. We report on our experience in imaging these microcirculation pattern in vivo using simultaneous confocal Fluorescein (FA)- and Indocyaninegreen (ICG) angiography before and after brachytherapy. The simultaneously procured confocal FA- and ICG angiograms of 50 patients with untreated choroidal melanomas were studied for the visibility of microcirculation pattern. Patients were also followed with simultaneous FA/ICG after brachytherapy. Confocal FA disclosed signs of tumor vascularization in 12 (24%) of the 50 examined patients but microcirculation pattern only in 3 patients (6%). In contrast, simultaneously obtained confocal ICG disclosed microcirculation pattern in 47 patients (94%). In 10 (77%) of the 13 patients the tumor microcirculation changed considerably after brachytherapy: Distortion, thickening, thinning, as well as complete obliteration of vessels could be observed. Histologically demonstrated microcirculation pattern can be imaged in vivo. This offers the possibility to assess the likely biologic behavior of the individual tumor without the need for obtaining a cytologic or histologic specimen via enucleation or fine-needle biopsy. Confocal ICG angiogiography images microcirculation pattern better than FA which can be explained by the different absorption-, fluorescence- and exudation-characteristics ICG. Follow-up with confocal ICG of choroidal melanomas after brachytherapy shows different features and allows for visualization of the microcirculation reaction to the treatment which might be a useful tool for studying the effects of future anti-angiogenesis based tumor therapies.

Monitoring of Tumor Microcirculation during Fractionated Radiation Therapy in Patients with Rectal Carcinoma: Preliminary Results and Implications for Therapy

To measure microcirculatory changes during chemoirradiation and to correlate perfusion index (PI) values with therapy outcome. Perfusion data in 11 patients with cT3 (clinical staging, tumor invaded the perirectal tissue) rectal carcinoma who underwent preoperative chemoirradiation were analyzed. Perfusion data were acquired by using a T1 mapping sequence with a whole-body magnetic resonance (MR) imager. After contrast medium was intravenously infused at a constant rate, concentration-and-time curves were evaluated for arterial blood and tumor. All patients underwent MR imaging before and at constant intervals during chemoirradiation. Clinical stages before therapy were compared with surgical stages after therapy. Spatial and temporal resolution on dynamic T1 maps were sufficient to reveal changes in contrast medium accumulation in the tumor. Comparison of PI values and radiation dose showed a significant increase in the 1st (P: =.003) and 2nd weeks (P: =.01) of treatment; values subsequently returned to pretreatment levels or showed a renewed increase. High initial PI values correlated with greater lymph node downstaging (P: =.042). Dynamic T1 mapping provides a suitable tool for monitoring tumor microcirculation during chemoirradiation and offers the potential for individual optimization of therapeutic procedures. Furthermore, these results indicate that the PI map may serve as a prognostic factor.

Trafficking of 'immune' CD4(+)/CD8(+)T-lymphocytes into the RENCA tumour microcirculation in vivo in mice.

RENCA-IL-2 (Murine Renal Cell Carcinoma transfected with murine IL-2 gene) cells were rejected by immunocompetent (but not T-cell deficient) Balb/c mice, which developed ‘immunity’ to subsequent parental RENCA tumour cell challenge. Splenocytes adoptively transferred this immunity. CD4+ and CD8+ T-lymphocytes prepared from the spleens of ‘tumour immune’ mice were evaluated for their ability to traffic into the tumour environment using an in vivo model that enables visualization of events within the microvasculature. RENCA cells were implanted into the mouse cremaster muscle and the trafficking of syngeneic lymphocyte subpopulations, derived from naive and ‘immune’ animals, into both the RENCA tumour and the surrounding normal cremaster muscle microcirculation was measured by in vivo microscopy. Fluorescently labelled CD4+ and CD8+ T lymphocytes taken from the spleens of naive mice or mice previously immunized with RENCA-IL-2 were injected systemically into tumour-bearer mice. Naive effector cells migrated to, and flowed through both the tumour and the normal microcirculation, with negligible adhesion. However we observed the selective recruitment, localization and arrest of immune CD4+ and CD8+ T lymphocytes (P < 0.05) into the tumour microcirculation, and in some instances the subsequent extravasation of cells into the tumour interstitium. Lymphocyte rolling by ‘immune’ CD4+ and CD8+ T-cells in the tumour microcirculation was greatly reduced, suggesting impaired adhesion molecule expression on the tumour endothelium. This study clearly demonstrates, by direct in vivo microscopy assessment, the localization of effector cells, CD4+ and CD8+ lymphocytes into tumours. © 2000 Cancer Research Campaign

Vascular structure and microcirculation of experimental pancreatic carcinoma in rats.

To study angiogenesis and microcirculation in experimental pancreatic carcinoma. Open experimental study. 2 University hospitals, Germany and USA. 16 male Lewis rats. Induction of a duct-like pancreatic cancer in the pancreas and peritoneum by interposition of fragments of tumour between 2 inert transparent polymethylmethacrylate plates. Microcirculation in the tumour and interaction between leucocytes, tumour, and endothelium investigated by intravital microscopy. The density of vessels in the carcinoma was significantly less than in normal pancreatic tissue (p = 0.0004). The vasculature of the tumour was characterised by a lack of differentiation in architecture of vessels, formation of sinusoidal and lacunar vessels and sudden changes in diameter of vessels. Red blood cell velocity differed among tumour vessels, but mean values were similar to those of normal exocrine pancreas. The mixed lymphocyte culture test indicated that the cell line DSL6A was immunogenic. However, high-affinity leucocyte-endothelium-interaction was significantly reduced in the tumour's microcirculation after both orthotopic and heterotopic implantation (p = 0.002). Rates of apoptosis were suppressed in heterotopic tumours compared with orthotopic ones. Tumour growth was faster in heterotopic tumours. Experimental duct-like pancreatic carcinoma can be differentiated from normal pancreas by: chaotic arrangement of vessels with loss of differentiation of architecture and heterogeneous distribution; the formation of sinusoidal or lacunar vessels; lower vascular density with similar erythrocyte velocity; increase in mean diameter of vessels; reduced leucocyte-endothelium interaction despite confirmed immunogeneity independent of wall shear rates. The site of implantation influences apoptosis and growth rates.