Rat Liver Tumor Model Research Articles

Hepatic arterial infusion (HAI) with PEGylated liposomes containing 5-FU improves tumor control of liver metastases in a rat model

To investigate the cytostatic effect of 5-fluorouracil (5-FU) encapsulated in polyethylene glycol (PEG) liposomes with or without degradable starch microspheres (DSM) in a long-term trial using a rat liver tumor model. The cytostatics were applied once either as a hepatic arterial infusion (HAI) or were systemically infused via the tail vein. Seven groups were compared with respect to tumor growth and survival times: 5-FU HAI (group I), 5-FU + DSM HAI (group II), PEG-5-FU HAI (group III), PEG-5-FU + DSM HAI (group IV), NaCl HAI (group V), 5-FU i.v. (group VI), and PEG-5-FU i.v. (group VII). Seven and 14 days after treatment in groups III and IV, only group IV had significantly inhibited tumor growth on day 21 compared to the groups treated intravenously. On day 28, none of the animals from the intravenously treated groups were still alive compared to a significantly longer survival time of 6 and 8 weeks in groups III and IV. Locoregional therapy with 5-fluorouracil encapsulated in PEGylated liposomes may further improve the treatment success with longer-lasting tumor regression and prolonged survival times.

Abstract No. 150: The tissue permeabilizer cyclopentadecanolide reduces the threshold temperature required to ablate tumors in a rat liver tumor model

Abstract No. 150: The tissue permeabilizer cyclopentadecanolide reduces the threshold temperature required to ablate tumors in a rat liver tumor model

Abstract No. 146: MRI and 3D finite element modeling for prediction of irreversible electroporation ablation zones: Feasibility studies in a rat liver tumor model

Abstract No. 146: MRI and 3D finite element modeling for prediction of irreversible electroporation ablation zones: Feasibility studies in a rat liver tumor model

Reference region-based pharmacokinetic modeling in quantitative dynamic contract-enhanced MRI allows robust treatment monitoring in a rat liver tumor model despite cardiovascular changes

In this work, two pharmacokinetic modeling techniques, population arterial input function model, and reference region model, were applied to dynamic contract-enhanced MRI data, to test the influence of a change in heart rate on modeling parameters. A rat population arterial input function was generated by dynamic contrast-enhanced computed tomography measurements using the MR contrast agent gadolinium diethylenetriamine penta-acetic acid. Then, dynamic contract-enhanced MRI was used for treatment monitoring in two groups of hepatocellular carcinoma bearing rats. Whereas group 1 had the same heart rate as animals analyzed for the population arterial input function (263 ± 20 bpm), group 2 had a higher heart rate (369 ± 11 bpm) due to a different anesthesia protocol. The pharmacokinetic modeling parameters volume transfer constant K(trans) and relative extravascular extracellular space v(e) were calculated with both models and statistically compared. For group 1, good correlation and agreement was found between the models showing no difference in K(trans) and v(e) (ΔK(trans): 4 ± 19% and Δv(e): 4 ± 12%, P = 0.2). In contrast, for group 2, a bias in parameter values for the population arterial input function model was detected (ΔK(trans): -45 ± 7% and Δv(e): -31 ± 7%, P ≤ 0.001). The presented work underlines the value of the reference region model in longitudinal treatment monitoring and provides a straightforward approach for the generation of a rat population arterial input function.

Interferon-alpha exhibits dual effects in a rat liver tumor model with liver cirrhosis

Interferon-alpha exhibits dual effects in a rat liver tumor model with liver cirrhosis

Imaging Hypoxia in Orthotopic Rat Liver Tumors with Iodine 124–labeled Iodoazomycin Galactopyranoside PET

To evaluate iodine 124 (124I)-labeled iodoazomycin galactopyranoside (IAZGP) positron emission tomography (PET) in the detection of hypoxia in an orthotopic rat liver tumor model by comparing regions of high (124)I-IAZGP uptake with independent measures of hypoxia and to determine the optimal time after injection to depict hypoxia. The institutional animal care and use committee approved this study. Morris hepatoma tumors were established in the livers of 15 rats. Tumor oxygenation was measured in two rats with a fluorescence fiberoptic oxygen probe. (124)I-IAZGP was coadministered with the established hypoxia markers pimonidazole and EF5 in nine rats; 12-hour PET data acquisition was performed 24 hours later. Tumor cryosections were analyzed with immunofluorescence and autoradiography. In the four remaining rats, serial 20- and 60-minute PET data acquisition was peformed up to 48 hours after tracer administration. Oxygen probe measurements showed severe hypoxia (<1 mm Hg) distributed evenly throughout tumor tissue. Analysis of cryosections showed diffuse homogeneous uptake of (124)I-IAZGP throughout all tumors. The (124)I-IAZGP distribution correlated positively with pimonidazole (r = 0.78) and EF5 (r = 0.76) distribution. Tracer uptake in tumors was detectable with PET after 24 hours in seven of nine rats. In rats that underwent serial PET, tumor-to-liver contrast was sufficient to enable detection of hypoxia between 6 and 48 hours after tracer administration. The optimal ratio between signal intensity and tumor-to-liver contrast occurred 6 hours after tracer administration. Regions of high (124)I-IAZGP uptake in orthotopic rat liver tumors are consistent with independent measures of hypoxia; visualization of hypoxia with (124)I-IAZGP PET is optimal 6 hours after injection.

Magnetic Resonance Imaging of Liver Metastases: Experimental Comparison of Anionic and Conventional Superparamagnetic Iron Oxide Particles With a Hepatobiliary Contrast Medium During Dynamic and Uptake Phases

To assess the contrast-enhancing effects of citrate-coated superparamagnetic iron oxide particles (VSOP-C184) in a rat liver tumor model using dynamic and delayed magnetic resonance imaging in comparison to carboxydextran-coated particles (ferucarbotran) and a hepatobiliary contrast medium (gadobenate dimeglumine). A total of 32 male rats with liver tumors (CC-531 colorectal carcinoma) were examined at 1.5 T with a T1-weighted dynamic series (3D gradient echo sequence) and T1-weighted and T2*-weighted images (2D gradient echo sequences) before and 15 and 90 minutes after injection. VSOP-C184 was investigated at doses of 0.015, 0.045, and 0.06 mmol Fe/kg, ferucarbotran at 0.015 mmol Fe/kg, and gadobenate dimeglumine at 0.025, 0.05, and 0.1 mmol Gd/kg. Liver-tumor contrast-to-noise ratio (CNR) was calculated and statistically compared. T1-weighted dynamic images: VSOP-C184 has significantly higher CNR values at a dose of 0,015 mmol Fe/kg than ferucarbotran at the same dose (P = 0.001). VSOP-C184 produces a significantly higher CNR at a dose of 0.045 mmol Fe/kg than gadobenate dimeglumine at a dose of 0.05 mmol Gd/kg (P = 0.019). At a dose of 0.06 mmol Fe/kg, the CNR for VSOP-C184 is significantly lower than that of gadobenate dimeglumine (0.1 mmol Gd/kg) (P = 0.005).T2-weighted delayed images: CNR values of VSOP-C184 are similar to those of ferucarbotran and are significantly higher than those of gadobenate dimeglumine (P < 0.05). On T1-weighted magnetic resonance imaging of liver tumors VSOP-C184 produces a high contrast comparable to that of a hepatobiliary contrast medium in addition to its contrast-enhancing effect in T2-weighted imaging.

Biodistribution and Bioactivity of Tetra-pegylated Meta-tetra(hydroxyphenyl)chlorin Compared to Native Meta-tetra(hydroxyphenyl)chlorin in a Rat Liver Tumor Model

Biodistribution and Bioactivity of Tetra-pegylated Meta-tetra(hydroxyphenyl)chlorin Compared to Native Meta-tetra(hydroxyphenyl)chlorin in a Rat Liver Tumor Model

Marked suppression of tumor growth by FTY720 in a rat liver tumor model: the significance of down-regulation of cell survival Akt pathway.

We aim to investigate the anticancer effect of a novel immunomodulator FTY720 on a rat orthotopic liver tumor model. A buffalo rat orthotopic liver tumor model was established by injection of a buffalo hepatoma cell line MH7777 into the right portal vein. FTY720 was administered by intraperitoneal injection starting at 10 days after tumor cell injection at a dosage of 5 mg/kg/day. FTY720 markedly suppressed tumor growth and inhibited tumor progression by selective induction of apoptosis of tumor cells via down-regulation of phospho-Akt(ser473) and up-regulation of cleaved caspase-3, together with decrease of focal adhesion kinase. Moreover, the proliferation index of tumor cells was significantly reduced to 15.92+/-5.03% by FTY720 compared with that of 42.92+/-4.47% in the control group (p<0.001). In addition, we confirmed that FTY720 caused no effect on infiltrated lymphocyte in tumor tissue. We conclude that FTY720 is an effective anticancer agent for liver tumor in a rat model without affecting the immune system of the host.

Ischemia-reperfusion of small liver remnant promotes liver tumor growth and metastases—Activation of cell invasion and migration pathways

Elucidating the mechanism of liver tumor growth and metastasis after hepatic ischemia-reperfusion (I/R) injury of a small liver remnant will lay the foundation for the development of therapeutic strategies to target small liver remnant injury, and will reduce the likelihood of tumor recurrence after major hepatectomy or liver transplantation for liver cancer patients. In the current study, we aimed to investigate the effect of hepatic I/R injury of a small liver remnant on liver tumor development and metastases, and to explore the precise molecular mechanisms. A rat liver tumor model that underwent partial hepatic I/R injury with or without major hepatectomy was investigated. Liver tumor growth and metastases were compared among the groups with different surgical stress. An orthotopic liver tumor nude mice model was used to further confirm the invasiveness of the tumor cells from the above rat liver tumor model. Significant tumor growth and intrahepatic metastasis (5 of 6 vs. 0 of 6, P=0.015), and lung metastasis (5 of 6 vs. 0 of 6, P=0.015) were found in rats undergoing I/R and major hepatectomy compared with the control group, and was accompanied by upregulation of mRNA levels for Cdc42, ROCK (Rho kinase), and vascular endothelial growth factor, as well as activation of hepatic stellate cells. Most of the nude mice implanted with liver tumor from rats under I/R injury and major hepatectomy developed intrahepatic and lung metastases. In conclusion, hepatic I/R injury of a small liver remnant exacerbated liver tumor growth and metastasis by marked activation of cell adhesion, invasion, and angiogenesis pathways.

Arteriolovenular Shunting Critically Determines Shutdown of Microcirculation Upon Cryotherapy in Tumor-Bearing Rat Liver

Tissue destruction by cryosurgery not only is mediated by direct cell damage, but also involves secondary mechanisms, such as ischemia due to shutdown of the microcirculation. Clinicians favor repetitive cryoapplication, although there is no proven evidence for a more effective tumor eradication. The aims of this study were (1) to establish a rat liver tumor model that allows for intravital microscopic analysis of hepatic tumor microcirculation and (2) to elucidate critical determinants of shutdown of microvascular perfusion after single and repetitive cryotherapy. In WAG-Rji rats (n = 14), syngeneic colon carcinoma cells (CC531) were implanted into the left liver lobe. Hepatic and tumor microcirculation were studied by intravital microscopy. Two weeks after implantation, the tumors had developed a microvasculature with a capillary density markedly (P < .05) lower compared with the sinusoidal density of normal liver. However, at the tumor margin, venule diameters were significantly enlarged (P < .05), with high red blood cell velocities and arteriolovenular shunts. Both freeze procedures (temperature at the tumor margin: -32.4 degrees C +/- 1.6 degrees C and -36.4 degrees C +/- 2.0 degrees C) resulted in a complete shutdown of intratumoral and peritumoral capillary and hepatic sinusoidal perfusion. In contrast, some large venules showed maintenance of blood flow initially after freezing (15 minutes); however, this was abolished during the subsequent 2-hour observation period. Enlarged high-flow venules at the tumor margin, which participate in arteriolovenular shunting, critically determine the shutdown of the microcirculation upon cryotherapy. Repetitive freezing is not more effective than a single-freeze procedure to achieve complete tumor microcirculatory stasis.

Hepatic artery infusion of antisense oligodeoxynucleotide and lipiodol mixture transfect liver cancer in rats

To study the distribution and stability of antisense oligodeoxynucleotide (ASODN) in Walker-256 cells and their distribution in liver, lung and kidney tissues after being infused alone or mixed with lipiodol via hepatic artery in a rat liver tumor model. 5'-Isothiocyanate (FITC)-labeled vascular endothelial growth factor (VEGF) ASODN was added into Walker-256 cell culture media. Its distribution in cells was observed by fluorescence microscope at different time points. Walker-256 carcinosarcoma was transplanted into Wistar rat liver to establish a liver cancer model. 5'-FITC-labeled VEGF ASODN mixed with (mixed group, n = 6) or without (TAI group, n = 6) ultra-fluid lipiodol was administrated via hepatic artery. Frozen samples of liver, lung and kidney tissue were taken from rats after 1, 3 and 6 d, respectively. The distribution of ASODN was observed under fluorescent microscope. ASODN could enter cytoplasm within 2 h and nuclei within 6 h. Accumulation of ASODN reached the peak point in nuclei at 12 h, and then disappeared gradually. No fluorescence could be seen in cells at 48 h. In vivo experiment, on d 1 and 3 the fluorescence staining in liver was stronger in mixed group than in TAI group and more fluorescence could be detected in lung and kidney in TAI group than in mixed group. On d 6, no fluorescence could be detected in TAI group, but faint fluorescence could be seen in mixed group. ASODN could be seen in cancer cells and normal hepatic cells. In mixed group, ASODN was mainly distributed in liver tumor tissues. ASODN can transfect Walker-256 cells. ASODN mixed with lipiodol infusion via hepatic artery can be used in the treatment of HCC.

Biodistribution of 10B in a rat liver tumor model following intra-arterial administration of sodium borocaptate (BSH)/degradable starch microspheres (DSM) emulsion

We reported that intra-arterial administration of borocaptate sodium (BSH)/lipiodol emulsion provided selectively high 10B concentrations (approximately 200 ppm 6 h after administration) in experimental liver tumors. In the present study, we investigated the pharmacokinetics of BSH following intra-arterial administration of BSH with other embolizing agent, degradable starch microspheres (DSM). The 10B concentration in the tumor at 1 h after administration of BSH with DSM was 231 ppm. At 6 h, the 10B concentration in the tumor in BSH with DSM group was 81.5 ppm. The 10B concentration in the liver at 1 h after administration of BSH with DSM was 184 ppm. At 6 h, the 10B concentration in the liver in BSH with DSM group was 78 ppm. The tumor/liver 10B concentration ratios (T/L ratio) in the “BSH+DSM” group were significantly smaller than those in the “BSH+lipiodol” group at 1 h (1.4 vs. 3.6) and 6 h (1.1 vs. 14.9). BSH/DSM-boron neutron capture therapy (BNCT) was not suitable for treatment of multiple liver tumors due to the low T/L 10B concentration ratio. However, the high 10B accumulation in the liver tumors following intra-arterial administration of BSH/DSM emulsion suggests that BSH/DSM-BNCT has the potential for application to malignant tumors in other sites.

Intra-arterial administration of sodium borocaptate (BSH)/lipiodol emulsion delivers B-10 to liver tumors highly selectively for boron neutron capture therapy: experimental studies in the rat liver model

Purpose Boron neutron capture therapy (BNCT) is particle radiotherapy with alpha ( 4He) particle and recoiled lithium nucleus ( 7Li) derived from a reaction of boron ( 10B) and thermal neutron. We investigated applying BNCT to malignant liver tumors. The purpose of the present study was to reveal the efficacy for administration of emulsion of a boron compound (sodium borocaptate; BSH) and lipiodol via a hepatic artery using a rat liver tumor model. Methods and materials Rat liver tumors were developed by direct injection of Walker 256 cells into the liver parenchyma. BSH (75 mg/kg)/lipiodol (0.3 mL/kg) emulsion was administered via the hepatic artery. Boron concentrations in the tumors, liver, and blood were measured at 1, 6, and 12 h after administration. Neutron capture radiography (NCR) was taken to confirm the selective accumulation of 10B in the liver tumors. Results Boron concentrations in the liver tumors and the tumor/liver (T/L) boron concentration ratio at 1, 6, and 12 h after administration of BSH/lipiodol emulsion (concentration: T/L ratio) were 479.2 ppm: 4.0, 197.3 ppm: 14.9, and 96.5 ppm: 6.6, respectively. Highly selective irradiation was clearly demonstrated by the NCR images. Conclusions Intra-arterial administration of BSH/lipiodol emulsion is effective method for delivering high concentration of 10B selectively to the liver tumors.

An implantable rat liver tumor model for experimental transarterial chemoembolization therapy and its imaging features.

To establish an ideal implantable rat liver tumor model for interventional therapy study and examine its angiographic signs and MRI, CT features before and after embolization. Forty male Wistar rats were implanted with Walker-256 tumor in the left lateral lobe of liver. Digital subtraction angiography (DSA) and transarterial chemoembolization were performed on day 14 after implantation. Native computer tomography (CT, n=8) and native magnetic resonance (MR, n=40) were performed between the day 8 and day 21 after implantation. The radiological morphological characteristics were correlated with histological findings. Successful implantation was achieved in all forty rats, which was confirmed by CT and MRI. MR allowed tumor visualization from day 8 while CT from day 11 after implantation. The tumors were hypodensity on CT, hypointense on MR T1-weighted and hyperintense on T2-weighted. The model closely resembled human hepatocarcinoma in growth pattern and the lesions were rich in vasculature on angiography and got its filling mainly from the hepatic artery. Before therapy, tumor size was 211.9+/-48.7 mm(3). No ascites, satellite liver nodules or lung metastasis were found. One week after therapy, tumor size was 963.6+/-214.8 mm(3) in the control group and 356.5+/-78.4mm(3) in TACE group. Ascites (4/40), satellite liver nodules (7/40) or lung metastasis (3/40) could be seen on day 21. Walker-256 tumor rat model is suitable for the interventional experiment. CT and MRI are helpful in animal optioning and evaluating experimental results.

Selective radioprotection of hepatocytes by systemic and portal vein infusions of amifostine in a rat liver tumor model

Purpose: The tolerance of the liver to radiation is too low to permit an effective dose to be delivered to patients who have diffuse intrahepatic cancer. In this study we evaluated whether systemic or portal venous administration of the aminothiol compound, amifostine, could protect the normal liver from the effects of ionizing radiation without compromising tumor cell kill in a rat liver tumor model. Methods and Materials: Rats implanted with liver tumors were infused with 200 mg/kg amifostine over 15 min via the femoral or portal vein. The livers were irradiated with a single 6-Gy fraction 15–20 min after the termination of amifostine infusion. Protection of the liver was assessed by an in vitro hepatocyte micronucleus assay and tumor protection by an in vivo- in vitro clonogenic survival assay. Tissue levels of the active metabolite, free WR-1065, were determined in the tumor and in the normal liver using a specific HPLC assay with electrochemical detection. Results: After a 6-Gy fraction, the frequency of hepatocyte micronuclei after administration of saline, systemic amifostine, and portal venous amifostine was 18.7 ± 1%, 6.8 ± 1%, and 9.9 ± 2%, respectively, corresponding to a radiation equivalent effect of 6 Gy ± 0.5, 1.8 Gy ± 0.3, and 2.5 Gy ± 1.3, respectively. Both amifostine conditions showed considerably less radiation effect than saline-treated controls ( p < 0.01); the two amifostine conditions did not differ ( p = 0.3). The surviving fraction of tumor cells was not affected by amifostine treatment and was 0.03 ± 0.02 and 0.05 ± 0.03 for systemic and portal venous delivery and 0.06 ± 0.02 for control animals (ANOVA analysis showed no significant difference of the means p = 0.34). Portal venous delivery produced significantly less WR-1065 in the tumor compared to systemic administration (54 μM ± 36 vs. 343 μM ± 88, respectively, p = 0.03). Conclusions: Both systemic and portal venous administration of amifostine effectively protect hepatocytes from ionizing radiation without compromising tumor cell kill in a clinically relevant animal model. These findings suggest that amifostine may be a selective normal tissue radioprotectant in liver cancer and that regional/portal infusions may be preferable to systemic dosing.

Endogenous natural killer cells do not play a role in antitumor effects induced by interleukin-2 in a syngeneic rat colon tumor model.

Previous experiments in a syngeneic rat liver tumor model using the colon adenocarcinoma CC531 demonstrated that injection of interleukin-2 (IL-2) induced significant antitumor responses. Furthermore, it was found that this treatment strategy was accompanied by an increase in the number of natural killer (NK) cells in and around the tumor. In the present study, the role of endogenous NK cells in IL-2-mediated antitumor responses was further elucidated by depleting tumor-bearing rats of NK cells, using the anti-CD161A mouse IgG1 antibody 3.2.3. Rats were depleted either after or prior to tumor induction and subsequently treated with IL-2. The results demonstrated that depletion of NK cells in tumor-bearing rats did not influence IL-2-induced antitumor effects. In addition, injection of IL-2 in NK-cell-depleted rats induced repopulation of NK cells in the peripheral blood from 3 days on and further after the last injection with IL-2. Therefore, the possibility cannot be excluded that de novo recruited NK cells play a role in attaining IL-2 mediated antitumor effects, but NK cells, which were present before or during the start of IL-2 therapy, were not relevant.

Biodistribution and bioactivity of tetra-pegylated meta-tetra(hydroxyphenyl)chlorin compared to native meta-tetra(hydroxyphenyl)chlorin in a rat liver tumor model.

It has been proposed that the construction of a photosensitizer-polymer conjugate would lead to an increased selective retention of the drug in tumor tissue resulting in an enhancement of selective tumor destruction by light in photodynamic therapy. In this study the kinetics of a tetra-pegylated derivative of meta-tetra(hydroxyphenyl)chlorin (mTHPC-PEG) were compared with those of native meta-tetra(hydroxyphenyl)chlorin (mTHPC) in a rat liver tumor model. In addition, the time course of bioactivity of both drugs was studied in normal liver tissue. Pegylation of mTHPC resulted in a two-fold increase in the plasma half-life time, a five-fold decrease in liver uptake and an increase in the tumor selectivity at early time intervals after drug administration. However, although mTHPC concentrations in liver decrease rapidly with time, mTHPC-PEG liver concentrations increased as a function of time. This led to a loss of tumor selectivity at all but the earliest time points, whereas with mTHPC tumor selectivity increased with time. For both drugs the time course of bioactivity in the liver parallels drug concentration levels with extensive necrosis after irradiation of mTHPC-PEG-sensitized liver tissue up to drug-light intervals of 120 h. It is concluded that on balance mTHPC-PEG does not appear to show any benefits over native mTHPC for the treatment of liver tumors, as normal liver tissue accumulates the compound. However, pegylation is a potentially promising strategy with an increase in tumor selectivity and reduced liver uptake if accumulation in the liver can be prevented.

Characteristics of tumor infiltration by adoptively transferred and endogenous natural-killer cells in a syngeneic rat model: implications for the mechanism behind anti-tumor responses.

Interleukin-2-activated, cultured NK cells (A-NK) cells were adoptively transferred into a syngeneic rat liver-tumor model. The kinetics of tumor infiltration by NK cells, originating either from adoptively transferred or from endogenous sources, the localization of these cells in the tumor, and their interactions with extracellular-matrix proteins were studied by immunohistochemistry and transmission-electron microscopy. The adoptive transfer of A-NK cells via the hepatic artery and s.c. injections of IL-2 into rats bearing subcapsularly induced CC531 liver tumors, but also IL-2 monotherapy, resulted in a significant increase of the number of NK cells both at the tumor border and in the tumor center. The majority of tumor-infiltrating NK cells was present in the tumor stroma and only occasionally was an NK cell observed in a tumor nodule in direct contact with tumor cells. Observations by electron microscopy suggested that matrix proteins, abundantly present in the tumor stroma but absent in the tumor nodules, provide a substrate for migration of infiltrating cells, whereas tight structures of matrix proteins surrounding tumor nodules provide a barrier for establishment of direct NK-cell-to-tumor-cell-contact. Our results suggest that direct NK-cell-to-target-cell-contact-mediated lysis is of minor importance for attaining an anti-tumor effect in this model. We hypothesize that treatment of tumor-bearing rats with A-NK cells and/or IL-2 initiates a cascade of events (e.g., secretion of tumor-killing cytokines and/or infiltration of other immune cells) ultimately leading to tumor regression.

A technique for isolated liver perfusion in the rat with survival and results of cytotoxic drug perfusion on liver tumor growth

The toxic side effects of many chemotherapeutic agents prevent their use in high concentrations. Isolated perfusion techniques have been used most commonly for malignancies involving the extremities, but recently also for irresectable liver tumors. This paper describes a technique for in vivo isolated liver perfusion for 30 min with oxygenated blood through the portal vein and hepatic artery simultaneously. There was a 14% mortality rate. There was some initial hepatocellular death, which resolved quickly and did not seriously affect liver function. There was only a small leak from the perfusion system to the systemic circulation. We tested the system on an experimental liver tumor from a colonic adenocarcinoma. Perfusion with added 5-FU in a toxic dose of 70 mg/kg to the medium significantly retarded tumor growth evaluated 10 days after perfusion compared to rats perfused without 5-FU. This model closely resembles the technique applied clinically and will enable further work on effects of perfusion in an experimental rat liver tumor model.