Rabbit VX2 Carcinoma Research Articles

Ultrasound-guided percutaneous implantation of rabbit VX2 carcinoma, using a coaxial technique and gelfoam pellet injection combination to establish a rabbit liver tumor model.

PURPOSE We aimed to investigate the safety and tumor seeding rate of a coaxial implantation technique combined with injection of a gelfoam pellet in establishing a VX2 liver tumor model in rabbits. METHODS A VX2 liver tumor model was established in 60 male New Zealand white rabbits, which were randomly divided into 3 groups (20 in each group) based on implantation technique (all performed under ultrasound guidance): group A, single needle only; group B, single needle with injection of a gelfoam pellet; or group C, coaxial technique with injection of a gelfoam pellet. The rates of liver tumor formation and tumor seeding to extrahepatic tissues were compared 2 weeks after implantation. Data were also collected regarding procedure time, number of punctures, occurrence of complications, and mortality rate. RESULTS A VX2 liver tumor model was established in all 60 rabbits (100%, 60/60). Ectopic implantation rate was 70% (14/20) in group A, 35% (7/20) in group B, and 5% (1/20) in group C, with significant difference among the groups (p < 0.001). Post hoc analysis showed significant difference between group A and group C (p < 0.001). However, there were no significant differences between group B and group A or group C (p = 0.027, p = 0.048, respectively). There were no significant differences among the groups in terms of procedure time (p = 0.405) or number of punctures (p = 0.612). No complications or deaths occurred. CONCLUSION A coaxial technique with injection of a gelfoam pellet is an effective and safe method for VX2 liver tumor implantation in rabbits, and this technique can reduce the risk of tumor seeding to the abdominal wall and omentum.

Porphyrin-containing Gadolinium Complex as a Tumor-targeting Magnetic Resonance Imaging (MRI) Contrast Agent.

Gadolinium diethylenetriaminepentaacetic di[5-(4'-amidophenyl)-10,15,20- tris(4'-sulfonatophenyl) porphyrin trisodium salt] (Gd-DTPA-2APTSPP) was synthesized by the reaction of diethylenetriaminepentaacetic dianhydride with 5-(4'-aminophenyl)-10,15,20-tris(4'-sulfonatophenyl) porphyrin and subsequently chelation with gadolium chloride. This gadolinium complex was characterized and its properties in vitro and in vivo were also evaluated. Compared with Gd-DTPA, Gd-DTPA-2APTSPP possessed high relaxivity r1, low cytotoxicity to HeLa cells and high enhanced signal intensities of the VX2 carcinoma in rabbits for a prolonged time. Moreover, Gd-DTPA-2APTSPP can distinguish the VX2 carcinoma from the reactive hyperplasia incited by inflammation and normal tissues in rabbits. Therefore, Gd-DTPA-2APTSPP can be taken up selectively by tumors and show the potential as a tumor-targeting MRI contrast agent.

ウサギ VX2 移植頬粘膜癌の増殖に伴うリンパ管の構築と所属リンパ節への転移経路に関する組織学的研究

ウサギ VX2 移植頬粘膜癌の増殖に伴うリンパ管の構築と所属リンパ節への転移経路に関する組織学的研究

A small interfering RNA targeting vascular endothelial growth factor efficiently inhibits growth of VX2 cells and VX2 tumor model of hepatocellular carcinoma in rabbit by transarterial embolization-mediated siRNA delivery.

IntroductionHepatocellular carcinoma is currently the second leading cause of cancer-related deaths worldwide with an increasing incidence.ObjectiveThe objective of this study is to investigate the effect of vascular endothelial growth factor small interfering RNA (VEGF-siRNA) on rabbit VX2 carcinoma cell viability in vitro and the effect of transarterial embolization (TAE)-mediated VEGF-siRNA delivery on the growth of rabbit VX2 liver-transplanted model in vivo.MethodsQuantitative reverse transcription polymerase chain reaction, enzyme-linked immunosorbent assay, and Western blot technologies were used to detect the expression level of VEGF. TAE and computed tomography scan were used to deliver the VEGF-siRNA and detect the tumor volume in vivo, respectively. Microvessel density was detected by immunohistochemistry with CD34 antibody. A biochemical autoanalyzer was used to evaluate the hepatic and renal toxicity.ResultsThe designed VEGF-siRNAs could effectively decrease the expression levels of VEGF mRNA and protein in vitro and in vivo. In vitro, the viability of rabbit VX2 carcinoma cells was reduced by 38.5%±7.3% (VEGF-siRNA no 1) and 30.0%±5.8% (VEGF-siRNA no 3) at 48 hours after transfection. Moreover, in rabbit VX2 liver-transplanted model, the growth ratios of tumors at 28 days after TAE-mediated siRNA delivery were 155.18%±19.42% in the control group, 79.67%±19.63% in the low-dose group, and 36.09%±15.73% in the high-dose group, with significant differences among these three groups. Microvessel density dropped to 34.22±4.01 and 22.63±4.07 in the low-dose group and high-dose group, respectively, compared with the control group (57.88±5.67), with significant differences among these three groups. Furthermore, inoculation of VX2 tumor into the liver itself at later stage induced significant increase in alanine aminotransferase and aspartate aminotransferase, indicating an obvious damage of liver functions, while treatment of VX2 tumor via TAE-mediated VEGF-siRNA had no toxicity to the livers and kidneys of rabbits, and VEGF-siRNA had the ability to protect liver damage induced by tumor growth.ConclusionThis is the first study to demonstrate that targeting VEGF via TAE-mediated siRNA delivery may become a powerful new option for effective treatment of hepatocellular carcinoma in the clinic.

In vitro and in vivo magnetic resonance imaging with chlorotoxin-conjugated superparamagnetic nanoprobes for targeting hepatocarcinoma.

The present study aimed to assess the in vitro and in vivo magnetic resonance imaging (MRI) features of chlorotoxin (CTX)-conjugated superparamagnetic iron oxide (SPIO) nanoprobes. CTX-conjugated nanoprobes were composed of SPIO coated with polyethylene glycol (PEG) and conjugated with CTX. The nanoprobes were termed SPIO-PEG-CTX. MRI of the SPIO and SPIO-PEG-CTX solutions at a different concentration was performed with a 3.0-T MRI scanner (Philips Achieva 3.0T X Series; Phillips Healthcare, The Netherlands). Rabbit VX2 hepatocarcinoma was established by a traditional laparotomy method (injection of the tumor particles into the liver using a 15G syringe needle) following approval by the institutional animal care and use committee. Contrast-enhanced MRI of VX2 rabbits (n=8) was performed using the same MRI scanner with SPIO‑PEG-CTX solutions as the contrast agent. Data were analyzed with calibration curve and a paired t-test. The SPIO-PEG-CTX nanoparticles were successfully prepared. With increasing concentrations of the solutions, the MRI signal intensity was increased at T1WI, but decreased at T2WI, which were the same as that for SPIO. Rabbit VX2 carcinoma appeared as a low MRI signal at T1WI, and high at T2WI. After injection of the contrast agent, the MRI signal of carcinoma was decreased relative to that before injection at T2WI (1,161±331.5 vs. 1,346±300.5; P=0.004<0.05), while the signal of the adjacent normal hepatic tissues was unchanged (480.6±165.1 vs. 563.4±67.8; P=0.202>0.05). The SPIO-PEG-CTX nanoparticles showed MRI negative enhancement at T2WI and a targeting effect in liver cancer, which provides the theoretical basis for further study of the early diagnosis of hepatocellular carcinoma.

Establishment of the retroperitoneal lymph node metastasis model of endometrial VX2 carcinoma in rabbits and observation of its metastatic features.

BackgroundThe objective of this study is to establish the retroperitoneal lymph node metastasis model of endometrial VX2 carcinoma in rabbits and observe of its metastatic features.MethodsThe VX2 cells were transplanted into the uterine muscularis mucosae of 48 rabbits by injecting carcinoma mass suspension. According to time, the rabbits were killed after the transplantation of VX2 cells, and they were divided into six groups, 15-, 18-, 21-, 24-, 27-, and 30-day group, and six rabbits in each group. Control groups consisted of those receiving no treatment or an injection of saline. The specimens of transplanted endometrial carcinoma and retroperitoneal lymph node in the rabbits were examined histopathologically after they were killed.ResultsAll rabbits developed VX2 endometrial carcinoma which was confirmed with pathological examination. Significantly increased tumor volume was observed at day 24, 27, and 30 post-injection of VX2 cells (P < 0.05). The retroperitoneal lymph nodes were not enlarged completely in each rabbit in the 15-day group, partly enlarged in the 18- and 21-day group, and all enlarged in the 24-, 27-, and 30-day group. The histopathological examination revealed no complete retroperitoneal lymph node metastasis in the 15- and 18-day group, partial metastasis in the 21-day group, and complete metastasis in the 24-, 27-, and 30-day group.ConclusionsThe model was established successfully by injecting carcinoma mass suspension, and various retroperitoneal lymph node metastasis model of endometrial VX2 carcinoma can be established rapidly in a month after the transplantation.

Malignant Bone Tumor Intramedullary Invasion

The aim of this study was to investigate the usefulness of dual-energy computed tomography (CT) spectral imaging for differentiating intramedullary microscopic invasion from simple marrow edema in a rabbit VX2 carcinoma model. VX2 tumors were implanted into the right tibiae of 30 New Zealand white rabbits. After 4 weeks, single-source dual-energy spectral CT was performed, and tumor specimens were cut into sagittal sections and partitioned into pathological slices. Multiplanar reconstruction images corresponding to the sagittal sections were selected for dot-to-dot comparisons to determine the macroscopic tumor, transition, and normal marrow areas. The regions of interest were classified into the above 3 areas according to the pathological maps to construct the CT spectral curves, and the slopes of the curves were calculated. The slope of the spectral curve in the transition area (7.78 ± 3.40) was significantly greater than that in the macroscopic tumor area (3.71 ± 2.15) and smaller than that in the normal marrow area (12.88 ± 4.12) (P < 0.001). Regarding the transition area, the slope of the spectral curve of the microscopic tumor invasion zone (10.87 ± 2.69) was greater than that of the simple bone marrow edema zone (5.84 ± 2.11) (P < 0.001). The properties of transition areas (microscopic invasion or simple bone marrow) can be determined by comparing spectral curves generated using dual-energy CT.

Comparison of drug release and pharmacokinetics after transarterial chemoembolization using diverse lipiodol emulsions and drug-eluting beads.

In many studies for chemoembolization of hepatocellular carcinoma, the Lipiodol emulsion preparation protocols, especially the mixing steps, were unclear or even unrevealed at all. However, doxorubicin (DOX) release may depend on the composition and volume ratio (Lipiodol to DOX solution) of a Lipiodol emulsion. Therefore, we conducted a preclinical study to compare in-vitro drug release and in-vivo pharmacokinetics of DOX from diverse Lipiodol emulsions and drug-eluting beads (DEBs) and to compare the tumor response in a rabbit VX2 carcinoma model. DOX release profiles of four types of Lipiodol emulsions with different media (normal saline or Pamiray as an iodinated contrast medium), volume ratio (Lipiodol to DOX solution), and DEBs were investigated in-vitro. For the in-vivo study, 15 rabbits bearing VX2 carcinoma in the liver were treated with 4∶1 volume ratio Lipiodol emulsion (group A), 1∶1 volume ratio Lipiodol emulsion (group B), and DEBs (group C) chemoembolization. Blood and tissue sampling was conducted to evaluate DOX concentration in plasma and tissues, histological changes, and liver toxicity. The most stable emulsion was formed with Pamiray (including DOX) at a 4∶1 volume ratio. The AUC value of group A was significantly lower than that of group B (p = 0.003) but comparable to that of group C (p = 0.071). The Cmax value of group A was significantly different compared with those of group B (p = 0.004) and C (p = 0.015). The tissue drug concentration in group A was comparable to that in group C (p = 0.251). No viable tumor was detected in rabbits of group A and B. In group C, viable tumor less than 10% was seen in two of the five rabbits. There were no significant differences in liver enzyme levels after the procedure. In conclusion, DOX release and pharmacokinetics of presented emulsion systems depend substantially on their composition. Therefore, Lipiodol emulsion type should be considered when interpreting data and designing new studies dealing with chemoembolization.

Role of MR-DWI and MR-PWI in the radiotherapy of implanted pulmonary VX-2 carcinoma in rabbits.

To detect the activity of tumor cells and tumor blood flow before and after the radiotherapy of implanted pulmonary VX-2 carcinoma in rabbit models by using magnetic resonance diffusion-weighted imaging (MR-DWI) and magnetic resonance perfusion weighted imaging (MR-PWI), and to evaluate the effectiveness and safety of the radiotherapy based on the changes in the MR-DWI and MR-PWI parameters at different treatment stages. A total of 56 rabbit models with implanted pulmonary VX-2 carcinoma were established, and then equally divided into treatment group and control group. MR-DWI and MR-PWI were separately performed using a Philips Acheiva 1.5T MRI machine (Philips, Netherland). MRI image processing was performed using special perfusion software and the WORKSPACE advanced workstation for MRI. MR-DWI was applied for the observation of tumor signals and the measurement of apparent diffusion coefficient (ADC) values; whereas MR-PWI was used for the measurement of wash in rate (WIR), wash out rate (WOR), and maximum enhancement rate (MER). The radiation treatment was performed using Siemens PRIMUS linear accelerator. In the treatment group, the radiotherapy was performed 21 days later on a once weekly dosage of 1,000 cGy to yield a total dosage of 5,000 cGy. THE ADC PARAMETERS IN THE REGION OF INTEREST ON DWI WERE AS FOLLOWS: on the treatment day for the implanted pulmonary VX-2 carcinoma, the t values at the center and the edge of the lesions were 1.352 and 1.461 in the treatment group and control group (P>0.05). During weeks 0-1 after treatment, the t values at the center and the edge of the lesions were 1.336 and 1.137 (P>0.05). During weeks 1-2, the t values were 1.731 and 1.736 (P<0.05). During weeks 2-3, the t values were 1.742 and 1.749 (P<0.05). During weeks 3-4, the t values were 2.050 and 2.127 (P<0.05). During weeks 4-5, the t values were 2.764 and 2.985 (P<0.05). The ADC values in the treatment group were significantly higher than in the control group. After the radiotherapy (5,000 cGy), the tumors remarkably shrank, along with low signal on DWI, decreased signal on ADC map, and remarkably increased ADC values. As shown on PWI, on the treatment day for the implanted pulmonary VX-2 carcinoma, the t values of the WIR, WOR, and MER at the center of the lesions were 1.05, 1.31, and 1.33 in the treatment group and control group (P>0.05); in addition, the t values of the WIR, WOR, and MER at the edge of the lesions were 1.35, 1.07, and 1.51 (P>0.05). During weeks 0-1 after treatment, the t values of the WIR, WOR, and MER at the center of the lesions were 1.821, 1.856, and 1.931 (P<0.05); in addition, the t values of the WIR, WOR, and MER at the edge of the lesions were 1.799, 2.016, and 2.137 (P<0.05). During weeks 1-1 after treatment, the t values of the WIR, WOR, and MER at the center of the lesions were 2.574, 2.156, and 2.059 (P<0.05) and the t values of the WIR, WOR, and MER at the edge of the lesions were 1.869, 2.058, and 2.057 (P<0.05). During weeks 2-3 after treatment, the t values of the WIR, WOR, and MER at the center of the lesions were 2.461, 2.098, and 2.739 (P<0.05) and the t values of the WIR, WOR, and MER at the edge of the lesions were 2.951, 2.625, and 2.154 (P<0.05). During weeks 3-4 after treatment, the t values of the WIR, WOR, and MER at the center of the lesions were 2.584, 2.107, and 2.869 (P<0.05) and the t values of the WIR, WOR, and MER at the edge of the lesions were 2.057, 2.637, and 2.951 (P<0.05). During weeks 4-5 after treatment, the t values of the WIR, WOR, and MER at the center of the lesions were 2.894, 2.827, and 3.285 (P<0.05) and the t values of the WIR, WOR, and MER at the edge of the lesions were 3.45, 3.246, and 3.614 (P<0.05). After the radiotherapy (500 cGy), the tumors shrank on the T1WI, WIR, WOR, and MER; meanwhile, the PWI parameter gradually decreased and reached its minimum value. MR-DWI and MR-PWI can accurately and directly reflect the inactivation of tumor cells and the tumor hemodynamics in rabbit models with implanted pulmonary VX-2 carcinoma, and thus provide theoretical evidences for judging the clinical effectiveness of radiotherapy for the squamous cell carcinoma of the lung.

Intraperitoneal oxidative stress as an oncolytic immunomodulator?

Intraperitoneal oxidative stress effectively converts the immune response against the papillomavirus-associated rabbit VX2 carcinoma from tumor permissive to tumoricidal and leads to a sustainable oncolytic immune response that can be adoptively transferred.

Intraperitoneal oxidative stress in rabbits with papillomavirus-associated head and neck cancer induces tumoricidal immune response that is adoptively transferable.

How tumors evade or suppress immune surveillance is a key question in cancer research, and overcoming immune escape is a major goal for lengthening remission after cancer treatment. Here, we used the papillomavirus-associated rabbit auricular VX2 carcinoma, a model for studying human head and neck cancer, to reveal the mechanisms underlying the antitumorigenic effects of intraperitoneal oxidative stress following O3/O2-pneumoperitoneum (O3/O2-PP) treatment. Solid auricular VX2 tumors were induced in immune-competent adult New Zealand White Rabbits. Animals were O3/O2-PP- or sham-treated, after which they underwent tumor ablation upon reaching no-go criteria. CD3(+) tumor-infiltrating lymphocytes (TIL) were evaluated by immunohistochemistry, and expression levels of 84 immune response genes were measured by quantitative real-time PCR. Adoptive transfer of peripheral blood leukocytes (PBL)-derived from animals with tumor regression-into control animals with progressing tumors was implemented to assess acquired tumor resistance functionally. Auricular VX2 tumors regressing after O3/O2-PP treatment exhibited increased levels of CD3(+) TILs; they also exhibited enhanced expression of genes that encode receptors involved in pattern recognition, molecules that are required for antigen presentation and T cell activation, and inflammatory mediators. Adoptive cell transfer of PBLs from donor rabbits with regressing tumors to recipient rabbits with newly implanted VX2 carcinoma resulted in acquired tumor resistance of the host and tumor regression. Intraperitoneal oxidative stress effectively converts the immune response against the papillomavirus-associated rabbit VX2 carcinoma from tumor permissive to tumoricidal and leads to a sustainable, adoptively transferable oncolytic immune response.

Large animal model for retroperitoneal lymphatic and lung metastasis

Retroperitoneal lymph node and lung metastasis are important prognostic factors for gynecologic cancer. The present study aimed to develop a new animal model for retroperitoneal lymph node and lung metastasis. VX2 squamous cell carcinoma tumor tissues were injected into the left gastrocnemius muscle of 38 healthy female New Zealand white rabbits. Animals were randomized into three groups according to day of sacrifice: 1, day 19; 2, day 22; and 3, day 25. Implanted primary tumor (IPTu), left and right retroperitoneal lymph node volumes and lung wet weights were measured on the day of sacrifice. The IPTu and left and right retroperitoneal lymph node volumes increased in a time-dependent manner. In addition, the proportion of animals with metastasis to the left peritoneal lymph nodes and the number of nodes involved increased over time. For days 19, 22 and 25, the proportion of animals with nodal metastasis was 58.3, 84.6 and 100%, respectively, and the number of affected nodes (range) was 3 (2–3), 3 (3–5) and 4 (4–5), respectively. No metastasis was detected in the right peritoneal lymph nodes. Metastasis to the lungs also increased with time, but was not statistically significant at days 19, 22 and 25 with metastasis present in 33.3, 38.5 and 76.9% of animals, respectively. Rates of metastases to the left retroperitoneal lymph nodes and lungs were found to positively correlate with the volumes (r=0.416 and 0.449, respectively). The current study assessed the characterization of a rabbit VX2 carcinoma model. This animal model is likely to be useful for evaluating retroperitoneal lymph node and lung metastasis.

Iodine quantification with dual-energy CT: phantom study and preliminary experience with VX2 residual tumour in rabbits after radiofrequency ablation.

The purpose of our study was to validate iodine quantification in a phantom study with dual-source dual-energy CT (DECT) and to apply this technique to differentiate benign periablational reactive tissue from residual tumour in VX2 carcinoma in rabbits after radiofrequency ablation (RFA). We applied iodine quantification with DECT in a phantom and in VX2 carcinoma in rabbits after incomplete RFA to differentiate benign periablational reactive tissue from residual tumour and evaluated its efficacy in demonstrating response to therapeutic RFA. A series of tubes containing solutions of varying iodine concentration were scanned with DECT. The iodine concentration was calculated and compared with known true iodine concentration. Triple-phase contrast-enhanced DECT data on 24 rabbits with VX2 carcinoma were then assessed at Day 3 (n=6), 1 week (n=6), 2 weeks (n=6) and 3 weeks (n=6) after incomplete RFA independently by 2 readers. Dual-energy postprocessing was used to produce iodine-only images. Regions of interest were positioned on the iodine image over the lesion and, as a reference, over the aorta, to record iodine concentration in the lesion and in the aorta. The pathological specimens were sectioned in the same plane as DECT imaging, and the lesion iodine concentration and lesion-to-aorta iodine ratio of residual tumour and benign periablational reactive tissue were assessed. There was excellent correlation between calculated and true iodine concentration (r=0.999, p<0.0001) in the phantom study. The lesion iodine concentration and lesion-to-aorta iodine ratio in residual tumour were significantly higher than in benign periablational reactive tissue in the 2-week group during the arterial phase (AP) (p<0.01) and in the 3-week group during both the AP (p<0.05) and the portal venous phase (p<0.05). There was no significant difference between them with respect to the lesion iodine concentration or lesion-to-aorta iodine ratio in the 3-day and 1-week groups. Iodine quantification with DECT is accurate in a phantom study and can be used to differentiate benign periablational reactive tissue from residual tumour in VX2 carcinoma in rabbits after RFA. Iodine quantification with DECT may help in differentiating benign periablational reactive tissue from residual tumour in VX2 carcinoma in rabbits after RFA.

Porphyrin-containing polyaspartamide gadolinium complexes as potential magnetic resonance imaging contrast agents

Porphyrin-containing polyaspartamide ligands (APTSPP–PHEA–DTPA) were synthesized by the incorporation of diethylenetriaminepentaacetic acid (DTPA) and 5-(4′-aminophenyl)-10,15,20-tris(4′-sulfonatophenyl) porphyrin, trisodium salt (APTSPP) into poly-α,β-[N-(2-hydroxyethyl)- l-aspartamide] (PHEA). These ligands were further reacted with gadolinium chloride to produce macromolecule-gadolinium complexes (APTSPP–PHEA–DTPA–Gd). Experimental data of 1H NMR, IR, UV and elemental analysis evidenced the formation of the polyaspartamide ligands and gadolinium complexes. In vitro and in vivo property tests indicated that APTSPP–PHEA–DTPA–Gd possessed noticeably higher relaxation effectiveness, less toxicity to HeLa cells, and significantly higher enhanced signal intensities (SI) of the VX2 carcinoma in rabbits with lower injection dose requirement than that of Gd–DTPA. Moreover, APTSPP–PHEA–DTPA–Gd was found to greatly enhance the contrast of MR images of the VX2 carcinoma, providing prolonged intravascular duration, and distinguished the VX2 carcinoma and normal tissues in rabbits according to MR image signal enhancements. These porphyrin-containing polyaspartamide gadolinium complexes can be used as the candidates of contrast agents for targeted MRI to tumors.

Dextran Gadolinium Complexes as Contrast Agents for Magnetic Resonance Imaging to Sentinel Lymph Nodes

The aim was to investigate three dextran gadolinium complexes Dextran-DTPA-Gd as the potential MRI contrast agents in lymphatic system. Three dextran gadolinium complexes Dextran-DTPA-Gd containing differing amounts of Gd-DTPA were synthesized by the incorporation of Gd-DTPA to the hydroxyl groups of dextran. These dextran ligands and gadolinium complexes were characterized, and their properties in vitro and in vivo were also evaluated. Dextran-DTPA-Gd demonstrated obviously higher relaxation effectiveness than that of Gd-DTPA. The result of in vitro cytotoxicity assay showed that these macromolecular ligands and their corresponding gadolinium complexes had low cytotoxicity to HeLa cells. Dextran-DTPA-Gd greatly enhanced the contrast of MR images of normal politeal lymph nodes and reactive hyperplasia of politeal lymph nodes in rabbits and provided prolonged duration in lymphatic system with lower injection doses than that of Gd-DTPA. However, Dextran-DTPA-Gd displayed low signal enhancements in MR images of politeal lymph nodes with VX2 carcinoma in rabbits during the detection time. These dextran gadolinium complexes Dextran-DTPA-Gd can be taken up selectively by lymphatic system and showed the potential as MRI contrast agents in lymphatic system.

Conductive interstitial thermal therapy (CITT) inhibits recurrence and metastasis in rabbit VX2 carcinoma model

Purpose: To investigate the potential of conductive interstitial thermal therapy (CITT) to inhibit recurrence and metastasis in a partially resected tumour model.Method: Fifteen New Zealand white rabbits were implanted with VX2 tumour intramuscularly in the rear thigh. Once the tumour size reached 20–25 mm in diameter, three animals were randomly selected to serve as controls, while the remaining animals were designated as the study group and treated with CITT. In the CITT group, the partially resected tumour and margins were thermally ablated. In the control group the tumour was partially resected to simulate positive margins. The animals were monitored for up to 12 weeks. At the endpoint, the animals were sacrificed, and whole-body diagnostic necropsy was conducted immediately.Results: Recurrences and metastatic lesions were observed in iliac and popliteal lymph nodes and abdomens of all control animals. In contrast, the observed rate of recurrence and metastatic lesion was 0% among CITT-treated animals, significantly less than the ≥50% null-hypothesis rate expected upon treatment failure (exact binomial P = 0.0002). Complete histopathological healing was obtained in 2 of 12 rabbits, and residual inflammation remained at the ablation site up to 12 weeks post-ablation in 10 of 12 rabbits. This pattern of necrosis and inflammatory response was not observed in any of the control rabbits.Conclusions: The CITT device effectively ablated partially resected VX2 carcinoma in a rabbit model, and inhibited recurrence and metastasis in this model. CITT evoked an inflammatory response that may be linked to the mechanism involved in reduced metastatic spread.

Model simulation and experimental validation of intratumoral chemotherapy using multiple polymer implants

Radiofrequency ablation has emerged as a minimally invasive option for liver cancer treatment, but local tumor recurrence is common. To eliminate residual tumor cells in the ablated tumor, biodegradable polymer millirods have been designed for local drug (e.g., doxorubicin) delivery. A limitation of this method has been the extent of drug penetration into the tumor (<5 mm), especially in the peripheral tumor rim where thermal ablation is less effective. To provide drug concentration above the therapeutic level as needed throughout a large tumor, implant strategies with multiple millirods were devised using a computational model. This dynamic, 3-D mass balance model of drug distribution in tissue was used to simulate the consequences of various numbers of implants in different locations. Experimental testing of model predictions was performed in a rabbit VX2 carcinoma model. This study demonstrates the value of multiple implants to provide therapeutic drug levels in large ablated tumors.

A function blocking anti-mouse integrin α5β1 antibody inhibits angiogenesis and impedes tumor growth in vivo

BackgroundIntegrins are important adhesion molecules that regulate tumor and endothelial cell survival, proliferation and migration. The integrin α5β1 has been shown to play a critical role during angiogenesis. An inhibitor of this integrin, volociximab (M200), inhibits endothelial cell growth and movement in vitro, independent of the growth factor milieu, and inhibits tumor growth in vivo in the rabbit VX2 carcinoma model. Although volociximab has already been tested in open label, pilot phase II clinical trials in melanoma, pancreatic and renal cell cancer, evaluation of the mechanism of action of volociximab has been limited because this antibody does not cross-react with murine α5β1, precluding its use in standard mouse xenograft models.MethodsWe generated a panel of rat-anti-mouse α5β1 antibodies, with the intent of identifying an antibody that recapitulated the properties of volociximab. Hybridoma clones were screened for analogous function to volociximab, including specificity for α5β1 heterodimer and blocking of integrin binding to fibronectin. A subset of antibodies that met these criteria were further characterized for their capacities to bind to mouse endothelial cells, inhibit cell migration and block angiogenesis in vitro. One antibody that encompassed all of these attributes, 339.1, was selected from this panel and tested in xenograft models.ResultsA panel of antibodies was characterized for specificity and potency. The affinity of antibody 339.1 for mouse integrin α5β1 was determined to be 0.59 nM, as measured by BIAcore. This antibody does not significantly cross-react with human integrin, however 339.1 inhibits murine endothelial cell migration and tube formation and elicits cell death in these cells (EC50 = 5.3 nM). In multiple xenograft models, 339.1 inhibited the growth of established tumors by 40–60% (p < 0.05) and this inhibition correlates with a concomitant decrease in vessel density.ConclusionThe results herein demonstrate that 339.1, like volociximab, exhibits potent anti-α5β1 activity and confirms that inhibition of integrin α5β1 impedes angiogenesis and slows tumor growth in vivo.

Volociximab, a chimeric integrin alpha5beta1 antibody, inhibits the growth of VX2 tumors in rabbits

Angiogenesis, the process by which new blood vessels form from existing vasculature, is critical for tumor growth and invasion. Growth factors, such as VEGF, initiate signaling cascades resulting in the proliferation of resting endothelial cells. Blockade of growth factor pathways has proven effective in inhibiting angiogenesis and tumor growth in vivo. Integrins, including the integrin alpha5beta1, are also important mediators of angiogenesis and these adhesion molecules also regulate cancer cell growth and migration in vitro. Volociximab is a high affinity, function-blocking antibody against integrin alpha5beta1 that is currently in multiple Phase II oncology clinical trials. Volociximab displays potent anti-angiogenic activity in a monkey model of choroidal neovascularization. In this study, we explored the consequences of integrin alpha5beta1 blockade on tumorigenesis. Because volociximab does not cross-react with rodent alpha5beta1, the syngeneic rabbit VX2 carcinoma model was utilized as an alternative to standard mouse xenograft models for the assessment of anti-tumor activity of volociximab. Volociximab administered intravenously to rabbits bearing VX2 tumors is detectable on tumor cells and vasculature 45 min post-administration. Volociximab was found to significantly inhibit the growth of tumors growing subcutaneously or intramuscularly, despite a 20-fold lower affinity for rabbit integrin, relative to human. This effect was found to correlate with decreased blood vessel density within these tumors. These results support the use of volociximab in the intervention of malignant disease.

VX2 Carcinoma in Rabbits after Radiofrequency Ablation: Comparison of MR Contrast Agents for Help in Differentiating Benign Periablational Enhancement from Residual Tumor

To prospectively compare the accuracy of a blood pool agent, SH L 643A, with that of gadopentetate dimeglumine in differentiating benign periablational enhancement from residual tumor in VX2 carcinomas in rabbits after radiofrequency (RF) ablation. Experiment was approved by the animal care committee. Sequential MR images were obtained before and with SH L 643A (17 000 Da, 0.05 mmol/kg) and, after a 24-hour interval, gadopentetate dimeglumine (546 Da, 0.1 mmol/kg) in 12 rabbits with VX2 carcinoma in the back muscle prior to (n = 12) and early (n = 12), 1 week (n = 8), and 4 weeks (n = 4) after RF ablation. RF ablation was performed with output of 90 W but at less than 300 seconds to ensure incomplete tumor ablation. The pathologic specimens were sectioned in the same plane as MR imaging, and the enhancement ratios (ie, the ratios of postcontrast to precontrast signal intensity) and the microvessel densities of residual tumor and benign periablational enhancement were assessed. With SH L 643A, the peak enhancement ratios of residual tumor (1.64 +/- 0.31 [standard deviation]) were significantly higher than those of benign periablational enhancement (0.97 +/- 0.16) (P < .001). With gadopentetate dimeglumine, the peak enhancement ratios of residual tumor (1.82 +/- 0.33) were not different from those of benign periablational enhancement (1.71 +/- 0.36). In benign periablational enhancement, enhancement ratios with injection of SH L 643A were lower than those with injection of gadopentetate dimeglumine for all time points up to 30 minutes (P < .05). The microvessel density was 25.72 +/- 5.43 vessels per field of view for residual tumor and 10.37 +/- 2.88 vessels per field of view for benign periablational enhancement (P < .001). Blood pool contrast agent SH L 643A permits more accurate differentiation of benign periablational enhancement from residual tumor compared with the extracellular agent gadopentetate dimeglumine.