Walker 256/B malignant breast cancer cells improve femur angioarchitecture and disrupt hematological parameters in a rat model of tumor osteolysis.

This study was designed to assess femur angioarchitecture and hematological effects of Walker 256/B cells in a rat model of tumor osteolysis. Tumor osteolysis was induced by in situ inoculation of Walker 256/B malignant cells. Six other rats were sham operated and served as control. Twenty days later, rats were euthanized, and femurs were collected than radiographed. Angioarchitecture [mean lumen diameter (MLD), wall thickness (WTh), Vessel number, volume, and separation (VNb, VV, and VSp respectively)] was studied by histomorphometry at 2 different positions (P1: diaphysis, and P2: metaphysis) of the operated femora. Some hematological parameters were also assessed. Walker 256/B induced marked tumor osteolysis, with cortical perforation and trabecular destruction, associated increase in bone vascularization (increases of VNb and VV and decrease of VSp). Angioarchitecture of W256/B rats was disorganized and showed large MLD and lower WTh. These effects were more prominent in P2. When compared to Sham group, significantly decreases at levels of red blood cell (RBC), hemoglobin (Hb), hematocrit (Ht), and white blood cell (WBC) were observed in W256/B rats. These results suggest that Walker 256/B cells induced tumor osteolysis, improve hypervasculature especially near the tumoral foci (P2) associated hematological disruption. Besides, tumor vessels showed abnormal (enlarged and thinner) and disorganized morphology.

Fingolimod potentiates the effects of sunitinib malate in a rat breast cancer model.

Most of the antiangiogenic strategies used in oncology principally target endothelial cells through the vascular endothelial growth factor (VEGF) pathway. Multiple kinase inhibitors can secondarily reduce mural cell stabilization of the vessels by blocking platelet-derived growth factor receptor (PDGFR) activity. However, sphingosine-1-phosphate (S1P), which is also implicated in mural cell recruitment, has yet to be targeted in clinical practice. We therefore investigated the potential of a simultaneous blockade of the PDGF and S1P pathways on the chemotactic responses of vascular smooth muscle cells (VSMCs) and the resulting effects of this blockade on breast tumor growth. Due to crosstalk between the S1P and PDGF pathways, we used AG1296 and/or VPC-23019 to inhibit PDGFR-ß and S1PR1/S1PR3 receptors, respectively. We showed that S1PR1 and S1PR3 are the principal receptors that mediate the S1P chemotactic signal on rat VSMCs and that they act synergistically with PDGFR-ß during PDGF-B signaling. We also showed that simultaneous blockade of the PDGFR-ß and S1PR1/S1PR3 signals had a synergistic effect, decreasing VSMC migration velocity toward endothelial cell and breast carcinoma cell-secreted cytokines by 65-90%. This blockade also strongly decreased the ability of VSMCs to form a three-dimensional cell network. Similar results were obtained with the combination of sunitinib malate (a VEGFR/PDGFR kinase inhibitor) and fingolimod (an S1P analog). Sunitinib malate is a clinically approved cancer treatment, whereas fingolimod is currently indicated only for treatment of multiple sclerosis. Orally administered, the combination of these drugs greatly decreased rat breast tumor growth in a syngeneic cancer model (Walker 256). This bi-therapy did not exert cumulative toxicity and histological analysis of the tumors revealed normalization of the tumor vasculature. The simultaneous blockade of these signaling pathways with sunitinib malate and fingolimod may provide an effective means of reducing tumor angiogenesis, and may improve the delivery of other chemotherapies.

[Destruction of Walker-256 tumor vasculature by a novel ultrasound cavitation technique].

OBJECTIVE: To explore the feasibility of disrupting tumor microcirculation by the cavitation of microbubbles enhanced ultrasound (US) and analyze its pathological mechanism. METHODS: Twenty-four SD male rats with subcutaneously transplanted Walker-256 tumor were divided into 3 groups, i.e. ultrasound plus microbubbles group (US + MB), US group and sham group. Pulsed US was delivered to tumor for 3 minutes during an intravenous infusion of microbubbles at 0.2 ml/kg in the US + MB group. The control groups received only the US exposure or the MB injection. Tumor perfusion was visualized with contrast enhanced ultrasound before and 0 min after treatment. Finally the pathological examination was performed. RESULTS: The contrast perfusion of Walker-256 tumors vanished immediately after treatment in the US + MB group and the gray scale value (GSV) decreased from 121 ± 12 (pre-treatment) to 81 ± 9 (post-treatment, P < 0.01). There was no significant difference of GSV before and after treatment in two control groups (P > 0.05). The GSV values were 112 ± 14 and 111 ± 12 pre-treatment and 113 ± 14 and 103 ± 13 post-treatment in the sham and US groups. The pathological examination showed remarkable hemorrhage, endothelial injuries, increased intercellular edema and in situ thrombosis. CONCLUSION: Microbubble-enhanced ultrasound can significantly disrupt tumor vasculature and block its circulation. And it may become a novel physical anti-angiogenetic therapy for tumor.

Biological Principles of Stereotactic Body Radiation Therapy (SBRT) and Stereotactic Radiation Surgery (SRS): Indirect Cell Death.

PURPOSE: To review the radiobiological mechanisms of stereotactic body radiation therapy stereotactic body radiation therapy (SBRT) and stereotactic radiation surgery (SRS). METHODS AND MATERIALS: We reviewed previous reports and recent observations on the effects of high-dose irradiation on tumor cell survival, tumor vasculature, and antitumor immunity. We then assessed the potential implications of these biological changes associated with SBRT and SRS. RESULTS: Irradiation with doses higher than approximately 10 Gy/fraction causes significant vascular injury in tumors, leading to secondary tumor cell death. Irradiation of tumors with high doses has also been reported to increase the antitumor immunity, and various approaches are being investigated to further elevate antitumor immunity. The mechanism of normal tissue damage by high-dose irradiation needs to be further investigated. CONCLUSIONS: In addition to directly killing tumor cells, high-dose irradiation used in SBRT and SRS induces indirect tumor cell death via vascular damage and antitumor immunity. Further studies are warranted to better understand the biological mechanisms underlying the high efficacy of clinical SBRT and SRS and to further improve the efficacy of SBRT and SRS.

Characteristic Blood-Perfusion Reduction of Walker 256 Tumor Induced by Diagnostic Ultrasound and Microbubbles.

Tumor angiogenesis is characterized by a defective, leaky and fragile microvascular construction, and microbubble-enhanced ultrasound (MEUS) with high-pressure amplitude is capable of disrupting tumor microvasculature and arresting blood perfusion. In this study, we tried to investigate whether the blood perfusion of a malignant tumor can be characteristically interrupted by combining microbubbles and diagnostic ultrasound (US). Twenty-nine Sprague-Dawley (SD) rats with subcutaneous Walker 256 tumors and seven healthy SD rats were included. Fifteen tumors were treated by MEUS, which combined constant microbubble injection and 20 episodes of irradiation by diagnostic US (i.e., acoustic radiation force impulse [ARFI] imaging). The other 14 tumors were treated by ARFI or sham US only. Seven skeleton muscles from healthy SD rats were also treated with MEUS, serving as the control. Contrast-enhanced ultrasound (CEUS) was performed before and after all treatments. The blood perfusion of the tumor MEUS group showed a significant drop immediately after treatment, followed by a quick, incomplete perfusion recovery within 10-20 min. The visual perfusion scoring result was consistent with the quantitative analysis by CEUS peak intensity. However, there were no significant perfusion changes in the tumor control groups or the muscle control group. Histologic examination found severe microvascular disruption and hemorrhage in the MEUS-treated tumors but not in the control groups. Therefore, the treatment combining diagnostic US and microbubbles can specifically decrease or interrupt the blood perfusion of Walker 256 tumors, which could be a potential new imaging method for diagnosing malignant tumors.

Radiopharmaceutical tracking of particles injected into tumors: a model to study clearance kinetics.

OBJECTIVES: Success of selective drug therapies depends on the drug's depot time in the target to treat. Depot time is currently being prolonged, using drug-eluting beads or microspheres for selective internal radiation therapy. The purpose of this study was to establish a model for investigating the depot time of particles injected into tumors in relation to tumor vascularization and particle size. MATERIALS AND METHODS: An animal model with two different vascularized tumors (Walker Carcinoma 256 (hypervascularized) and Yoshida Sarcoma (hypovascularized)) was used. The tumors were implanted into the hind leg of Wistar rats. When the tumors reached 10-15mm, rhenium radiolabeled particles of 25microm and 0.3microm were percutaneously injected into the tumors: large particles (Re-188 microspheres) in 10 hypo- and 10 hypervascularized tumors and small particles (Re-186 sulfid colloid) in 4 hypo- and 16 hypervascularized tumors with the co-injection of the vasoconstrictor, adrenalin (0.01 mg), into 8 hypervascularized tumors. Tumor activity was measured with a gamma camera at 10 min, 1h, 3h, 6h, 14h and 48h p.i. In addition, activity in the lung, liver, spleen, kidneys, and lymph nodes was measured at 48 h p.i. Measurements were adjusted for decay times and then compared. RESULTS: Drainage of the injected particles is bi-phasic, characterized by a fast wash-out. At 10 min p.i., intratumoral activity decreases to 70% of the initially injected activity. This is followed by a slow decline at 48 h p.i in which intratumoral activity decreases to at least 60% of the initially injected activity. Slow decline is independent of particle size and vascularization, whereas fast leakage depends on both. Co-injecting adrenalin significantly reduced the wash-out of the small particles. Radiolabeled microspheres accumulated mainly in the lungs, smaller colloids in the liver. CONCLUSIONS: Particle stay time, biodistribution, and stability can be easily monitored as shown in this animal model. The hematogeneous wash-out can be reduced, using larger particles and vasoconstrictors. Prolonged retention is independent of vascularization and particle size and appears to be sufficient for therapy.

Red propolis and L-lysine on angiogenesis and tumor growth in a new model of hamster cheek pouch inoculated with Walker 256 tumor cells.

OBJECTIVE: To evaluate the effect of red propolis and L-lysine on angiogenesis and tumor growth in a new model of hamster cheek pouch inoculated with Walker 256 tumor cells. METHODS: The study consisted of two experiments with four groups each (total: 57 hamsters). In the experiment 1, the animals were inoculated with Walker tumor cells, followed by administration of test substances (red propolis 200mg/5mL/kg or L-lysine 150mg/kg) or control substances (gum arabic 5mL/kg or water 5mL/kg) for 10 days. The animals in the experiment 2 received red propolis, L-lysine, gum arabic or water at the same doses, for 33 days prior to inoculation of Walker tumor cells, followed by 10 days of treatment with the same substances. Based on single-plane images, angiogenesis was quantified (mean vascular area), in percentage, and tumor area (mm2) and perimeter (mm). RESULTS: In the experiment 1, compared to animals receiving water, the mean vascular area expressed in percentage was significantly smaller in animal treated with propolis (p<0.05) and L-lysine (p<0.001). CONCLUSION: Both red propolis and L-lysine inhibited tumor angiogenesis in the new hamster cheek pouch model when administered after tumor inoculation.

[An experimental study of energy controllable steep pulse in the treatment of rat with subcutaneous transplantive tumor].

This experimental study was designed to investigate the effects and the expressions of microvessel density (MVD), vascular endothelial growth factor (VEGF) on the transplanted tumor in the rat model with Walker-256 after energy controllable steep pulse(ECSP). The experiment revealed that the steep pulse electrical field has better effect on tumor, compared with the control. The positive cell staining intensity of VEGF in the control group was significantly higher than that in ECSP group (P < 0.05). The number of MVD in the tumor tissues of ECSP group was significantly lower than that of tumor control group (P < 0.05). These results showed that ECSP could inhibit the growth and angiogenesis of tumor and its pathway is to down-regulate the expression of VEGF possibly.

Blood flow and heat transfer in Walker 256 mammary carcinoma.

True thermal conductivity of 13 Walker 256 mammary carcinomas in noninbred Sprague-Dawley rats averaged 3.2+/-0.9 mW/cm/degrees C under physiologic conditions. A comparison of the effective thermal conductivity in 4 tumors with and without blood flow revealed large differences ranging from 14 to 132%. When the blood supply to the tumor was doubled or reduced to one-half, the effective thermal conductivity varied proportionally to the square root of the perfusion rate. The values of thermal conductivity were obtained from a tumor preparation in which blood flow was monitored continuously during temperature changes. These changes were measured by thermistors and produced by thermal probes incorporated by the growing tumor, not surgically inserted within the tissue at the time of measurement. Inasmuch as tissue necrosis was not a dominant factor, the data are interpreted to reflect the degree of difference in local perfusion of the neoplastic tissue.

Blood flow in normal tissues and tumors during hyperthermia.

The effect of hyperthermia on the blood flow was studied in skin, muscle, and Walker 256 carcinoma implanted in the legs of SD rats. The radioactive microsphere method was used to measure the blood flow. Hyperthermia for 1 hour with water at 43 degrees C increased the blood flow in skin and muscle by about threefold to fourfold. On the contrary, hyperthermia had no appreciable effect on the blood flow in tumors. Consequently, during hyperthermia blood flow in the skin and muscle surrounding the tumors was greater than that in tumors larger than about 2 g. Despite the apparent increase in heat dissipation by the increased blood flow, the temperature of the skin was 42.6-42.8 degrees C, and the temperature at the core of tumors larger than 2 cm in diameter was 42.3-42.7 degrees C during the hyperthermia. The lower temperature in the muscle could be attributed to an increase in heat dissipation as a result of the increased blood flow. This differential rise in temperature by heating may account in part for the differential effect of hyperthermia on tumors and normal tissues in vivo.

Blood flow and venous pH of tissue-isolated Walker 256 carcinoma during hyperglycemia.

Hemodynamic (blood flow rate, hematocrit, hemoglobin concentration, and blood viscosity) and pH responses to glucose (6 g/kg, i.p.) injections were studied in ten Walker 256 carcinoma tumors (0.5-1.8 g) grown in the "tissue-isolated" tumor preparation. A maximum blood flow reduction of 57 +/- 19% (SD) occurred concurrently with an increase in tumor arterial-venous blood pH difference 20-30 min after glucose administration. Tumor venous blood pH dropped significantly by 0.15 +/- 0.07 pH unit to 7.15 +/- 0.01, while systemic blood pH dropped by 0.06 +/- 0.02 pH unit to 7.38 +/- 0.03. Arteriovenous blood pH differences were found to correlate with blood flow rates; however, both the small magnitude of the pH reduction and the immediate blood flow response argue against the hypothesis of increased resistance to flow caused by low pH-stiffened RBC membranes. Significant increases in systemic and tumor efferent whole blood viscosities at 2.25 and 4.5s-1 occurred after glucose administration, while hemoglobin concentrations of systemic and tumor efferent blood increased by as much as 11 +/- 1 and 16 +/- 2%, respectively. Venous to arterial hematocrit and hemoglobin ratios remained unchanged with glucose administration. These data suggest local tumor blood flow reductions are caused by increased viscous resistance to flow within the tortuous microvasculature of tumor, not as a result of low pH RBC rigidity, but rather from other mechanisms such as glucose-mediated RBC rigidity and systemic hemoconcentration.

Temperature and blood flow measurements in and around 7,12-dimethylbenz(a)anthracene-induced tumor and Walker 256 carcinosarcomas in rats.

By means of an implanted transmitter, a circadian rhythm of temperature was found both in 7,12-dimethylbenz(a)anthracene-induced tumors and in Walker 256 carcinosarcomas. There was no significant difference in the temperatures of the two tumors. The temperature was lowest in periods of rest, and the temperature difference between light and dark periods was about 1 degree. Both tumors were found to have a higher temperature than that of s.c. tissue. External temperature measurements of the skin covering the 7,12-dimethylbenz(a)anthracene-induced tumor by thermistor probe and by thermography showed a temperature 1-2 degrees below the temperature of surrounding skin areas. In the 7,12-dimethylbenz(a)anthracene-induced tumors the blood flow was low, which should correspond to a relatively small heat production, although the temperature was relatively high. Blood flow in skin overlying tumor was high, presumably a perifocal hyperemic reaction, although the temperature was relatively low in this area. Thus tissue temperatures was not indicative of blood flow.

Inhibition of angiogenesis by the matrix metalloprotease inhibitor N-[2R-2-(hydroxamidocarbonymethyl)-4-methylpentanoyl)]-L-tryptophan methylamide.

The inhibitor N-[2R-2-(hydroxamidocarbonymethyl)-4-methylpentanoyl)]-L- tryptophan methylamide specifically blocks several matrix metalloproteases, enzymes which are thought to be involved in angiogenesis. An extract of Walker 256 carcinoma in Hydron pellets implanted in the corneas of Sprague-Dawley rats was used to stimulate angiogenesis from the vessels of the limbus. Angiogenesis was graded visually as the distance penetrated into the cornea and the number of vessels generated. The vessel area was also measured by image analysis using Image 1 software. Continuous i.v. administration of N-[2-(hydroxamidocarbonymethyl)-4-methylpentanoyl)]- L-tryptophan methylamide at 32 mg/kg/day (n = 17) via syringe pump reduced vessel number [25.06 +/- 5.9 (SEM) compared to 65.33 +/- 9.0] and vessel area (26.14 +/- 3.2 mm2 compared with 40.96 +/- 4.6 mm2), but not distance penetrated, compared to vehicle-treated control eyes after 6 days. These results confirm the suspected role for matrix metalloproteases in angiogenesis and suggest that inhibitors of these enzymes may be angiostatic agents.

Bulk transfer of fluid in the interstitial compartment of mammary tumors.

Venous blood leaving a solid tumor showed higher erythrocyte concentration than did aortic blood. Net fluid loss of efferent blood as calculated from hematocrit differences was 2.7 to 6.7% of flow volume, 4.5 to 10.2% of perfusing plasma volume, or 0.14 to 0.22 ml fluid per hr per g in 2 to 5 g transplanted MTW9 and Walker 256 mammary carcinomas, and primary N-nitrosomethylurea- and 7,12-dimethylbenz(alpha)anthracene-induced mammary carcinomas of rats. Net fluid loss was directly related to blood flow but inversely related to tumor size. Increased hydrostatic pressure in tumor interstitial space was a consistent finding. Micropore chambers embedded in transplanted tumors drained 4 to 5 times more interstitial fluid than did identical chambers in the s.c. tissue. It is concluded that: (a) convective currents are present within the interstitial spaces of tumors; (b) the magnitude of fluid transfer can be measured by the difference in hemoconcentration between afferent and efferent tumor blood; and (c) the volume of this fluid transfer is not altered by hormone-induced tumor regression. The increased hydrostatic pressure of tumor interstitial spaces is interpreted as being due to absence of an anatomically well-developed lymphatic network. The bulk transfer of fluid within interstitial spaces is comparable to lymphatic drainage and should be considered in assessing drug concentration and distribution in solid tumors.

Increases in brain tumor and cerebral blood flow by blood-perfluorochemical emulsion (Fluosol-DA) exchange.

It has been suggested that oxygen-carrying blood substitutes, perfluorochemical (PFC) emulsions, can increase blood flow and oxygen delivery to poorly perfused tumor regions. Local cerebral blood flow was measured in male Wistar rats bearing intracranial Walker 256 tumor with and without blood-PFC exchange using [14C]iodoantipyrine (IAP) and quantitative autoradiographic techniques. The exchange transfusion was performed in two groups of awake animals breathing 100% oxygen: (a) complete blood-PFC exchange, hematocrit 4%; and (b) partial blood-PFC exchange, hematocrit 20-25%. The tissue/blood partition coefficient for IAP was determined in a separate set of experiments under identical conditions and was used in calculating blood flow. Cerebral blood flow increased approximately 2-fold following complete blood-PFC exchange and 1.5-fold by the partial exchange. A similar 1.5-fold increase in flow was measured in intraparenchymal tumors following partial exchange; however, a flow increase was not identified in the meningeal extension of the tumors. The increase in cerebral blood flow is consistent with an autoregulatory response of the central nervous system vasculature to maintain an adequate supply of oxygen to central nervous system tissue. Presumably, the increase in blood flow to the intracerebral tumor reflects the autoregulatory response of the host tissue. The effect of blood-PFC exchange on blood flow and drug delivery to tumor may depend on the particular tumor and its site of growth (host tissue). The tissue/blood partition coefficient for IAP increased from 0.8 to 1.0 and 1.4 following partial and complete blood-PFC exchange, respectively. This change in the partition coefficient reflects the change in the intravascular fraction of IAP that is bound to plasma proteins. The enhanced therapeutic effect that has been reported in some experimental tumor models may result from a higher tissue/blood equilibrium distribution ratio (due to reduced plasma protein binding) resulting in a higher tissue exposure to certain drugs following PFC administration.

Increased thermal response to ultrasound in the Walker carcinosarcoma treated with vasoactive drugs.

In order to evaluate the potential of a highly selective Ca2+ entry blocker (nisoldipine) and of 5-hydroxytryptamine (5-HT) as adjuvant in hyperthermia treatment, we studied the differential flow response and time-course of tumor and normal tissue temperature following the administration of the two substances and during ultrasound heating. In 12 rats bearing Walker 256 carcinomas i.p. injection of 0.2-0.4 mg/kg nisoldipine caused a reduction in the tumor-to-muscle flow relationship of 4.4 +/- 1.9 (SD) to 1.74 +/- 0.86 as determined by intraarterial 133Xe injection; i.p. injection of 2-8 mg/kg 5-HT (N = 13) caused a respective reduction from 3.9 +/- 2.67 to 1.3 +/- 1.59. During a 20-min period of 41 degrees C normal tissue temperature-controlled ultrasound heating without drugs, tumor temperature attained 40.8 +/- 0.9 degrees C (N = 16). Nisoldipine or 5-HT injection at continuing 41 degrees C normal tissue temperature controlled energy delivery produced an instantaneous further increment of tumor temperature, eventually to 44.0 +/- 1.14 degrees C or 44.2 +/- 1.26 degrees C, respectively, after a period of 20 min. Injection of 0.9% NaCl (N = 4) solution caused only insignificant changes. Blood pressure and muscle perfusion were distinctly influenced by nisoldipine, but not by 5-HT. Since both drugs instantaneously increased the temperature differential between tumor and normal tissue, though by different vasoaction, they should be considered as adjuvants in hyperthermia.

Disposition characteristics of macromolecules in the perfused tissue-isolated tumor preparation.

Disposition characteristics of model macromolecules with different physicochemical characteristics and macromolecular prodrugs of mitomycin C, namely mitomycin C-dextran conjugates, were studied in tissue-isolated tumor preparations of Walker 256 carcinoma with the use of a single-pass vascular perfusion technique. In constant infusion experiments, all radiolabeled macromolecules accumulated in the tumor tissue, but the degree and pattern of distribution greatly varied, depending on their electric charges. Positively charged macromolecules were markedly accumulated compared with those that were neutral or negatively charged. In addition, their concentrations were significantly higher in viable than in necrotic regions, while neutral and negative compounds were distributed in necrotic rather than in viable regions. Pharmacokinetic analysis of tissue concentration-time courses of positively charged diethylaminoethyl and neutral dextrans showed that their movement occurred by convective fluid flow, and that high tissue accumulation of positively charged macromolecules could be explained by strong binding due to electrostatic interaction. For neutral and anionic macromolecules with negligible affinity to the tissue, it was suggested that the final concentration gradient between the viable and necrotic regions was decided by their tissue fluid content. Thus, the present study revealed the basic disposition characteristics of macromolecules in tumor tissue relative to their physicochemical properties.

Effect of intravenous versus intraperitoneal glucose injection on systemic hemodynamics and blood flow rate in normal and tumor tissues in rats.

The effect of i.v. versus i.p. glucose injections on blood flow rate of Walker 256 carcinoma and several normal tissues of unanesthetized, unrestrained female Sprague-Dawley rats was measured, using the radioactive microsphere technique prior to and 60 min after glucose administration (6 g/kg, i.v. or i.p.). Changes in systemic hemodynamics were also investigated in an attempt to further quantify the mechanisms responsible for tumor blood flow reduction. Most of the normal tissues showed either no modification or a decrease in the blood flow rate following i.v. or i.p. glucose injections. The response was more pronounced following i.p. injection. Most of the tissues studied also exhibited significant modification in cardiac output distribution. A decrease in blood flow rate and cardiac output distribution was also observed in the tumors following i.v. or i.p. injections. However, as observed in the normal tissues, the response was more pronounced following i.p. injection. Mechanisms for blood flow reduction include systemic effects such as reduction and redistribution of cardiac output. An additional systemic mechanism following i.p. injection includes hypovolemic hemoconcentration which was evident by an increase in blood hematocrit. In rats, unlike observations in mice, the change in hematocrit following i.p. injection is not as large and cannot account for the total blood flow reduction. Local mechanisms include an increase in red blood cell rigidity due to glucose itself and tissue acidosis.

Disposition of anticancer drugs after bolus arterial administration in a tissue-isolated tumor perfusion system.

Disposition characteristics of various anticancer drugs in a tissue-isolated tumor preparation were studied in Walker 256 carcinosarcoma-bearing rats using an in situ single-pass vascular perfusion technique. Three anticancer drugs, 5-fluorouracil, mitomycin C, and Adriamycin, and two lipophilic prodrugs of mitomycin C were tested in the tumor preparation perfused with Tyrode's solution containing 4.7% bovine serum albumin. After bolus arterial injection of test drugs, their outflow concentration-time curves were analyzed based on statistical moment theory. In each tumor preparation, the injection of drug was paired with that of vascular reference substance, Evans' blue-labeled bovine serum albumin, and disposition parameters of the drug were corrected with those of vascular reference substance. From the mean transit time values of vascular reference substance, the average vascular volume of the tumor preparation was calculated to be 0.063 ml/g, which decreased with tumor growth. All drugs showed significant extraction by the tumor tissue, depending on their physicochemical properties. Distribution volumes of tested drugs were from 1.53 to 3.33 times larger than the vascular volume. Calculated intrinsic clearance values for the protein-unbound fractions increased as the lipophilicity of the drug increased. The potential increase in tumor uptake was observed in lipophilic prodrugs of mitomycin C. The present experimental system is thus suggested to be useful for analyzing drug disposition in tumor tissue.

Resting host and tumor perfusion as determinants of tumor vascular responses to norepinephrine.

Blood flow determinations and arteriograms were obtained in rat (Walker carcinoma) and rabbit (V2 carcinoma) liver tumors at rest and after norepinephrine administration. Resting tumor blood flow exceeded resting hepatic flow in both models, and both tumors responded with vasoconstriction and reduced blood flow. In tumors and the surrounding normal host tissue, the greater the perfusion prior to drug administration, the greater is the response (decrease in perfusion) to the vasoconstrictor. Although tumor perfusion decreased after vasoconstrictor, post-norepinephrine angiograms revealed an improved diagnostic image because of the enlarged but unresponsive tumor feeder vessels, persistent tumor blush, and simultaneous vasoconstriction in the normal liver. In these models, improved tumor visualization resulted even though a decrease in tumor blood flow had occurred. The angiographic image is related therefore to the lack of vasoconstriction in the tumor feeder vessel, which has, however, a decreased blood flow and the correspondingly greater volume of normally constricting hepatic arteries which results in a marked decrease in the background of vessels upon which the tumor image is superimposed.