Suppression of the growth and metastasis of mouse melanoma by Taenia crassiceps and Mesocestoides corti tapeworms

Cancer is still one of the leading causes of death, with an estimated 19.3 million new cases every year. Our paper presents the tumor-suppressing effect of Taenia crassiceps and Mesocestoides corti on B16F10 melanoma, the intraperitoneal application of which followed the experimental infection with these tapeworms, resulting in varying degrees of effectiveness in two strains of mice. In the case of M. corti-infected ICR mice, a strong tumor growth suppression occurred, which was accompanied by a significant reduction in the formation of distant metastases in the liver and lung. Tapeworm-infected C57BL/6J mice also showed a suppression of tumor growth and, in addition, the overall survival of infected C57BL/6J mice was significantly improved. Experiments with potential cross-reaction of melanoma and tapeworm antigens with respective specific antibodies, restimulation of spleen T cells, or the direct effect of tapeworm excretory-secretory products on melanoma cells in vitro could not explain the phenomenon. However, infections with T. crassiceps and M. corti increased the number of leukocytes possibly involved in anti-tumor immunity in the peritoneal cavity of both ICR and C57BL/6J mice. This study unveils the complex interplay between tapeworm infections, immune responses, and melanoma progression, emphasizing the need for further exploration of the mechanisms driving observed tumor-suppressive effects.

Pedunculoside inhibits epithelial-mesenchymal transition and overcomes Gefitinib-resistant non-small cell lung cancer through regulating MAPK and Nrf2 pathways

BACKGROUND

Lung cancer is the primary cause of cancer-related mortality worldwide owing to its strong metastatic ability. EGFR-TKI (Gefitinib) has demonstrated efficacy in metastatic lung cancer therapy, but most patients ultimately develop resistance to Gefitinib, leading to a poor prognosis. Pedunculoside (PE), a triterpene saponin extracted from Ilex rotunda Thunb., has shown anti-inflammatory, lipid-lowering and anti-tumor effects. Nevertheless, the therapeutic effect and potential mechanisms of PE on NSCLC treatment are unclear.

PURPOSE

To investigate the inhibitory effect and prospective mechanisms of PE on NSCLC metastases and Gefitinib-resistant NSCLC.

METHODS

In vitro, A549/GR cells were established by Gefitinib persistent induction of A549 cells with a low dose and shock with a high dose. The cell migratory ability was measured using wound healing and Transwell assays. Additionally, EMT-related Markers or ROS production were assessed by RT-qPCR, immunofluorescence, Western blotting, and flow cytometry assays in A549/GR and TGF-β1-induced A549 cells. In vivo, B16-F10 cells were intravenously injected into mice, and the effect of PE on tumor metastases were determined using hematoxylin-eosin staining, Caliper IVIS Lumina, DCFH₂-DA staining, and western blotting assays.

RESULTS

PE reversed TGF-β1-induced EMT by downregulating EMT-related protein expression through MAPK and Nrf2 pathways, decreasing ROS production, and inhibiting cell migration and invasion ability. Moreover, PE treatment enabled A549/GR cells to retrieve the sensitivity to Gefitinib and mitigate the biological characteristics of EMT. PE also significantly inhibited lung metastasis in mice by reversing EMT proteins expression, decreasing ROS production, and inhibiting MAPK and Nrf2 pathways.

CONCLUSIONS

Collectively, this research presents a novel finding that PE can reverse NSCLC metastasis and improve Gefitinib sensitivity in Gefitinib-resistant NSCLC through the MAPK and Nrf2 pathways, subsequently suppressing lung metastasis in B16-F10 lung metastatic mice model. Our findings indicate that PE is a potential agent for inhibiting metastasis and improving Gefitinib resistance in NSCLC.

In vivo micro-computed tomography imaging in liver tumor study of mice using Fenestra VC and Fenestra HDVC

Contrast agents are used to enhance the visibility of rodent organs during in vivo micro-computed tomography imaging. Specifically, this non-invasive technique can study liver tumor growth and progression in small animals. Fenestra VC and the novel Fenestra HDVC were compared for enhancement in the liver of healthy and tumor-bearing mice, and the images were compared for their ability to define the tumor border, volume and quantity of tumors. Fenestra VC and Fenestra HDVC were injected into healthy eight-week-old female mice (C57BL/6) via the tail vein then imaged at seven different time points. The experimental results showed that 0.005 mL/g of Fenestra HDVC resulted in the same enhancement for all eight organs as 0.01 mL/g of Fenestra VC across all time points. For the tumor study, B16F10 tumors were surgically introduced into ten eight-week-old female mice (C57BL/6) then imaged in vivo over a 3 day period. Ex vivo micro-CT images of the excised livers were also obtained. The tumor volume and quantity were measured in each image, and the tumour progression observed over 3 days. We showed Fenestra HDVC is effective for in vivo imaging in rodents because the optimal enhancement level in organs is maintained at a reduced injection volume.

CD47-SIRPα Checkpoint Disruption in Metastases Requires Tumor-Targeting Antibody for Molecular and Engineered Macrophage Therapies

The macrophage checkpoint interaction CD47-SIRPα is an emerging target for cancer therapy, but clinical trials of monoclonal anti-CD47 show efficacy only in liquid tumors when combined with tumor-opsonizing IgG. Here, in challenging metastatic solid tumors, CD47 deletion shows no effect on tumor growth unless combined with otherwise ineffective tumor-opsonization, and we likewise show wild-type metastases are suppressed by SIRPα-blocked macrophages plus tumor-opsonization. Lung tumor nodules of syngeneic B16F10 melanoma cells with CD47 deletion show opsonization drives macrophage phagocytosis of B16F10s, consistent with growth versus phagocytosis calculus for exponential suppression of cancer. Wild-type CD47 levels on metastases in lungs of immunocompetent mice and on human metastases in livers of immunodeficient mice show that systemic injection of antibody-engineered macrophages also suppresses growth. Such in vivo functionality can be modulated by particle pre-loading of the macrophages. Thus, even though CD47-SIRPα disruption and tumor-opsonizing IgG are separately ineffective against established metastatic solid tumors, their combination in molecular and cellular therapies prolongs survival.

Comprehensive chemical proteomics analyses reveal that the new TRi-1 and TRi-2 compounds are more specific thioredoxin reductase 1 inhibitors than auranofin

Anticancer drugs that target cellular antioxidant systems have recently attracted much attention. Auranofin (AF) is currently evaluated in several clinical trials as an anticancer agent that targets the cytosolic and mitochondrial forms of the selenoprotein thioredoxin reductase, TXNRD1 and TXNRD2. Recently, two novel TXNRD1 inhibitors (TRi-1 and TRi-2) have been developed that showed anticancer efficacy comparable to AF, but with lower mitochondrial toxicity. However, the cellular action mechanisms of these drugs have not yet been thoroughly studied. Here we used several proteomics approaches to determine the effects of AF, TRi-1 and TRi-2 when used at IC50 concentrations with the mouse B16 melanoma and LLC lung adenocarcinoma cells, as these are often used for preclinical mouse models in evaluation of anticancer drugs. The results demonstrate that TRi-1 and TRi-2 are more specific TXNRD1 inhibitors than AF and reveal additional AF-specific effects on the cellular proteome. Interestingly, AF triggered stronger Nrf2-driven antioxidant responses than the other two compounds. Furthermore, AF affected several additional proteins, including GSK3A, GSK3B, MCMBP and EEFSEC, implicating additional effects on glycogen metabolism, cellular differentiation, inflammatory pathways, DNA replication and selenoprotein synthesis processes. Our proteomics data provide a resource for researchers interested in the multidimensional analysis of proteome changes associated with oxidative stress in general, and the effects of TXNRD1 inhibitors and AF protein targets in particular.

Docetaxel and Lidocaine Co-Loaded (NLC-in-Hydrogel) Hybrid System Designed for the Treatment of Melanoma

Melanoma is the most aggressive skin carcinoma and nanotechnology can bring new options for its pharmacological treatment. Nanostructured lipid carriers (NLC) are ideal drug-delivery carriers for hydrophobic drugs, such as the antineoplastic docetaxel (DTX), and hybrid (NLC-in-hydrogel) systems are suitable for topical application. This work describes a formulation of NLC_DTX in xanthan-chitosan hydrogel containing lidocaine (LDC) with anticancer and analgesia effects. The optimized nanoparticles encapsulated 96% DTX and rheological analysis revealed inherent viscoelastic properties of the hydrogel. In vitro assays over murine fibroblasts (NIH/3T3) and melanoma cells (B16-F10), human keratinocytes (HaCaT) and melanoma cells (SK-MEL-103) showed reduction of docetaxel cytotoxicity after encapsulation in NLC_DTX and HGel-NLC_DTX. Addition of LDC to the hybrid system (HGel-NLC_DTX-LDC) increased cell death in tumor and normal cells. In vivo tests on C57BL/6J mice with B16-F10-induced melanoma indicated that LDC, NLC_DTX, HGel-NLC_DTX-LDC and NLC_DTX + HGel-LDC significantly inhibited tumor growth while microPET/SPECT/CT data suggest better prognosis with the hybrid treatment. No adverse effects were observed in cell survival, weight/feed-consumption or serum biochemical markers (ALT, AST, creatinine, urea) of animals treated with NLC_DTX or the hybrid system. These results confirm the adjuvant antitumor effect of lidocaine and endorse HGel-NLC_DTX-LDC as a promising formulation for the topical treatment of melanoma.

Evaluation of a xenogeneic vascular endothelial growth factor-2 vaccine in two preclinical metastatic tumor models in mice

In this study, a xenogeneic DNA vaccine encoding for human vascular endothelial growth factor receptor-2 (hVEGFR-2) was evaluated in two murine tumor models, the B16-F10 melanoma and the EO771 breast carcinoma model. The vaccine was administered by intradermal injection followed by electroporation. The immunogenicity and the biological efficacy of the vaccine were tested in (1) a prophylactic setting, (2) a therapeutic setting, and (3) a therapeutic setting combined with surgical removal of the primary tumor. The tumor growth, survival, and development of an immune response were followed. The cellular immune response was measured by a bioluminescence-based cytotoxicity assay with vascular endothelial growth factor-2 (VEGFR-2)-expressing target cells. Humoral immune responses were quantified by enzyme-linked immunosorbent assay (ELISA). Ex vivo bioluminescence imaging and immunohistological observation of organs were used to detect (micro)metastases. A cellular and humoral immune response was present in prophylactically and therapeutically vaccinated mice, in both tumor models. Nevertheless, survival in prophylactically vaccinated mice was only moderately increased, and no beneficial effect on survival in therapeutically vaccinated mice could be demonstrated. An influx of CD3+ cells and a slight decrease in VEGFR-2 were noticed in the tumors of vaccinated mice. Unexpectedly, the vaccine caused an increased quantity of early micrometastases in the liver. Lung metastases were not increased by the vaccine. These early liver micrometastases did however not grow into macroscopic metastases in either control or vaccinated mice when allowed to develop further after surgical removal of the primary tumor.

Imaging of Orthotopic Glioblastoma Xenografts in Mice Using a Clinical CT Scanner: Comparison with Micro-CT and Histology

Purpose

There is an increasing need for small animal in vivo imaging in murine orthotopic glioma models. Because dedicated small animal scanners are not available ubiquitously, the applicability of a clinical CT scanner for visualization and measurement of intracerebrally growing glioma xenografts in living mice was validated.

Materials and Methods

2.5x10⁶ U87MG cells were orthotopically implanted in NOD/SCID/ᵞc^-/- mice (n = 9). Mice underwent contrast-enhanced (300 μl Iomeprol i.v.) imaging using a micro-CT (80 kV, 75 μAs, 360° rotation, 1,000 projections, scan time 33 s, resolution 40 x 40 x 53 μm) and a clinical CT scanner (4-row multislice detector; 120 kV, 150 mAs, slice thickness 0.5 mm, feed rotation 0.5 mm, resolution 98 x 98 x 500 μm). Mice were sacrificed and the brain was worked up histologically. In all modalities tumor volume was measured by two independent readers. Contrast-to-noise ratio (CNR) and Signal-to-noise ratio (SNR) were measured from reconstructed CT-scans (0.5 mm slice thickness; n = 18).

Results

Tumor volumes (mean±SD mm³) were similar between both CT-modalities (micro-CT: 19.8±19.0, clinical CT: 19.8±18.8; Wilcoxon signed-rank test p = 0.813). Moreover, between reader analyses for each modality showed excellent agreement as demonstrated by correlation analysis (Spearman-Rho >0.9; p<0.01 for all correlations). Histologically measured tumor volumes (11.0±11.2) were significantly smaller due to shrinkage artifacts (p<0.05). CNR and SNR were 2.1±1.0 and 1.1±0.04 for micro-CT and 23.1±24.0 and 1.9±0.7 for the clinical CTscanner, respectively.

Conclusion

Clinical CT scanners may reliably be used for in vivo imaging and volumetric analysis of brain tumor growth in mice.

Lymph node biophysical remodeling is associated with melanoma lymphatic drainage

Tissue remodeling is a characteristic of many solid tumor malignancies including melanoma. By virtue of tumor lymphatic transport, remodeling pathways active within the local tumor microenvironment have the potential to be operational within lymph nodes (LNs) draining the tumor interstitium. Here, we show that lymphatic drainage from murine B16 melanomas in syngeneic, immune-competent C57Bl/6 mice is associated with LN enlargement as well as nonuniform increases in bulk tissue elasticity and viscoelasticity, as measured by the response of whole LNs to compression. These remodeling responses, which quickly manifest in tumor-draining lymph nodes (TDLNs) after tumor inoculation and before apparent metastasis, were accompanied by changes in matrix composition, including up to 3-fold increases in the abundance of soluble collagen and hyaluronic acid. Intranodal pressures were also significantly increased in TDLNs (+1 cmH2O) relative to both non-tumor-draining LNs (-1 cmH2O) and LNs from naive animals (-1 to 2 cmH2O). These data suggest that the reorganization of matrix structure, composition, and fluid microenvironment within LNs associated with tumor lymphatic drainage parallels remodeling seen in primary malignancies and has the potential to regulate the adhesion, proliferation, and signaling function of LN-resident cells involved in directing melanoma disease progression.

Longitudinal imaging of cancer cell metastases in two preclinical models: a correlation of noninvasive imaging to histopathology

Metastatic spread is the leading cause of death from cancer. Early detection of cancer at primary and metastatic sites by noninvasive imaging modalities would be beneficial for both therapeutic intervention and disease management. Noninvasive imaging modalities such as bioluminescence (optical), positron emission tomography (PET)/X-ray computed tomography (CT), and magnetic resonance imaging (MRI) can provide complementary information and accurately measure tumor growth as confirmed by histopathology. Methods. We validated two metastatic tumor models, MDA-MD-231-Luc and B16-F10-Luc intravenously injected, and 4T1-Luc cells orthotopically implanted into the mammary fat pad. Longitudinal whole body bioluminescence imaging (BLI) evaluated metastasis, and tumor burden of the melanoma cell line (B16-F10-Luc) was correlated with (PET)/CT and MRI. In addition, ex vivo imaging evaluated metastasis in relevant organs and histopathological analysis was used to confirm imaging. Results. BLI revealed successful colonization of cancer cells in both metastatic tumor models over a 4-week period. Furthermore, lung metastasis of B16-F10-Luc cells imaged by PET/CT at week four showed a strong correlation (R (2) = 0.9) with histopathology. The presence and degree of metastasis as determined by imaging correlated (R (2) = 0.7) well with histopathology findings. Conclusions. We validated two metastatic tumor models by longitudinal noninvasive imaging with good histopathology correlation.

Mammary cancer bone metastasis follow-up using multimodal small-animal MR and PET imaging

Despite tremendous progress in the management of breast cancer, the survival rate of this disease is still correlated with the development of metastases-most notably, those of the bone. Diagnosis of bone metastasis requires a combination of multiple imaging modalities. MR imaging remains the best modality for soft-tissue visualization, allowing for the distinction between benign and malignant lesions in many cases. On the other hand, PET imaging is frequently more specific at detecting bone metastasis by measuring the accumulation of radiotracers, such as (18)F-sodium fluoride ((18)F-NaF) and (18)F-FDG. Thus, the main purpose of this study was to longitudinally monitor bone tumor progression using PET/MR image coregistration to improve noninvasive imaging-assisted diagnoses.

METHODS

After surgical implantation of mammary MRMT-1 cells in a rat femur, we performed minimally invasive imaging procedures at different time points throughout tumor development. The procedure consisted of sequential coregistered MR and PET image acquisition, using gadolinium-diethylenetriaminepentaacetic acid (DTPA) as a contrast agent for MR imaging and (18)F-FDG, (11)C-methionine, and (18)F-NaF as molecular tracers for PET imaging. The animals were then euthanized, and complementary radiologic (micro-CT scans) and histologic analyses were performed.

RESULTS

In this preclinical study, we demonstrated that coregistered MR and PET images provide helpful information in a rat mammary-derived bone cancer model. First, MR imaging provided a high-definition anatomic resolution that made the localization of bone resorption and tumor extension detectable between days 9 and 18 after the injection of cancer cells in the medullary channel of the femur. Indeed, the calculation of mean standardized uptake value (SUVmean) and maximal SUV (SUVmax) in bone and soft-tissue regions, as defined from the gadolinium-DTPA contrast-enhanced MR images, showed (18)F-NaF uptake modifications and increased (18)F-FDG or (11)C-methionine uptake in the bone and surrounding soft tissues. (18)F-FDG and (11)C-methionine were compared in terms of the magnitude of change in their uptake and variability. We observed that (11)C-methionine SUVmean variations in the tumor were more important than those of (18)F-FDG. We also found fewer interindividual variations using SUVmean as a quantitative parameter than SUVmax.

CONCLUSION

This preclinical evaluation demonstrated that a PET/MR image coregistration protocol provided a powerful tool to evaluate bone tumor progression in a rat model of bone metastasis and that this protocol could be translated to improve the clinical outcome for metastatic breast cancer management.

Advances in multimodality molecular imaging of bone structure and function

The skeleton is important to the body as a source of minerals and blood cells and provides a structural framework for strength, mobility and the protection of organs. Bone diseases and disorders can have deteriorating effects on the skeleton, but the biological processes underlying anatomical changes in bone diseases occurring in vivo are not well understood, mostly due to the lack of appropriate analysis techniques. Therefore, there is ongoing research in the development of novel in vivo imaging techniques and molecular markers that might help to gain more knowledge of these pathological pathways in animal models and patients. This perspective provides an overview of the latest developments in molecular imaging applied to bone. It emphasizes that multimodality imaging, the combination of multiple imaging techniques encompassing different image modalities, enhances the interpretability of data, and is imperative for the understanding of the biological processes and the associated changes in bone structure and function relationships in vivo.

Investigating the effect of longitudinal micro-CT imaging on tumour growth in mice

The aim of this study is to determine the impact of longitudinal micro-CT imaging on the growth of B16F1 tumours in C57BL/6 mice. Sixty mice received 2 × 10(5) B16F1 cells subcutaneously in the hind flank and were divided into control (no scan), 'low-dose' (80 kVp, 70 mA, 8 s, 0.07 Gy), 'medium-dose' (80 kVp, 50 mA, 30 s, 0.18 Gy) and 'high-dose' (80 kVp, 50 mA, 50 s, 0.30 Gy) groups. All imaging was performed on a fast volumetric micro-CT scanner (GE Locus Ultra, London, Canada). Each mouse was imaged on days 4, 8, 12 and 16. After the final imaging session, each tumour was excised, weighed on an electronic balance, imaged to obtain the final tumour volume and processed for histology. Final tumour volume was used to evaluate the impact of longitudinal micro-CT imaging on the tumour growth. An ANOVA indicated no statistically significant difference in tumour volume (p = 0.331, α = β = 0.1) when discriminating against a treatment-sized effect. Histological samples revealed no observable differences in apoptosis or cell proliferation. We conclude that four imaging sessions, using standard protocols, over the course of 16 days did not cause significant changes in final tumour volume for B16F1 tumours in female C57BL/6 mice (ANOVA, α = β = 0.1, p = 0.331).

Histopathological follow-up by tissue micro-array in a survival study after melanoma treated by nanosecond pulsed electric fields (nsPEF)

A recent study has shown that nanosecond pulsed electric fields (nsPEF) can affect the intracellular structures of melanoma within weeks. nsPEF is a non-drug, non-thermal treatment using ultrashort, intense pulsed electric fields with nanosecond durations. In the current study we followed up melanoma histopathology and metastasis with tissue micro-array 5 months post-nsPEF. After nsPEF treatment, tumor growth, tumor histology, metastasis, peri-tumor vessel and micro-vessel density were examined for the effect of nsPEF treatment on melanoma in vivo. The 17 nsPEF-treated mice were tumor-free for 169 days, significantly longer than those 19 control mice bearing melanoma without nsPEF. Histopathology follow-up showed that melanoma did not recur to the primary injection place after complete elimination. Compared with the control tumor, nsPEF-treated tumors present decreased micro-vessel density in a time-course manner in this survival study. Treatment with nsPEF caused continuous histopathological changes in melanomas, eliminated melanoma without recurrence at the primary site and prolonged animal survival time by inhibiting tumor blood supply and leading to tumor infarction. Thus, nsPEF could be applied in a non-ionizing therapeutic approach, without other agents, to locally treat tumors within a defined boundary.

Gallium-67-labeled lactam bridge-cyclized alpha-melanocyte stimulating hormone peptide for primary and metastatic melanoma imaging

The purpose of this study was to examine the melanoma imaging properties of a novel 67Ga-labeled lactam bridge-cyclized alpha-melanocyte stimulating hormone (alpha-MSH) peptide. A lactam bridge-cyclized alpha-MSH peptide, DOTA-GlyGlu-CycMSH {DOTA-Gly-Glu-c[Lys-Nle-Glu-His-DPhe-Arg-Trp-Gly-Arg-Pro-Val-Asp]}, was synthesized and radiolabeled with 67Ga. The melanoma targeting and pharmacokinetic properties of 67Ga-DOTA-GlyGlu-CycMSH were determined in B16/F1 flank primary melanoma-bearing and B16/F10 pulmonary metastatic melanoma-bearing C57 mice. Flank primary melanoma and pulmonary metastatic melanoma imaging were performed by small animal single photon emission computed tomography (SPECT)/CT using 67Ga-DOTA-GlyGlu-CycMSH as an imaging probe. 67Ga-DOTA-GlyGlu-CycMSH was readily prepared with greater than 95% radiolabeling yield. 67Ga-DOTA-GlyGlu-CycMSH exhibited substantial tumor uptake (12.93 +/- 1.63%ID/g at 2 h postinjection) and prolonged tumor retention (5.02 +/- 1.35%ID/g at 24 h postinjection) in B16/F1 melanoma-bearing C57 mice. The uptake values for nontarget organs were generally low (<0.30%ID/g) except for the kidneys at 2, 4, and 24 h postinjection. 67Ga-DOTA-GlyGlu-CycMSH exhibited significantly (p < 0.05) higher uptakes (1.44 +/- 0.75%ID/g at 2 h postinjection and 1.49 +/- 0.69%ID/g at 4 h postinjection) in metastatic melanoma-bearing lung than those in normal lung (0.15 +/- 0.10%ID/g and 0.17 +/- 0.11%ID/g at 2 and 4 h postinjection, respectively). Both flank primary B16/F1 melanoma and B16/F10 pulmonary melanoma metastases were clearly visualized by SPECT/CT using 67Ga-DOTA-GlyGlu-CycMSH as an imaging probe 2 h postinjection. 67Ga-DOTA-GlyGlu-CycMSH exhibited favorable melanoma targeting and imaging properties, highlighting its potential as an effective imaging probe for early detection of primary and metastatic melanoma.

High throughput static and dynamic small animal imaging using clinical PET/CT: potential preclinical applications

PURPOSE

The objective of the study was to evaluate state-of-the-art clinical PET/CT technology in performing static and dynamic imaging of several mice simultaneously.

METHODS

A mouse-sized phantom was imaged mimicking simultaneous imaging of three mice with computation of recovery coefficients (RCs) and spillover ratios (SORs). Fifteen mice harbouring abdominal or subcutaneous tumours were imaged on clinical PET/CT with point spread function (PSF) reconstruction after injection of [18F]fluorodeoxyglucose or [18F]fluorothymidine. Three of these mice were imaged alone and simultaneously at radial positions -5, 0 and 5 cm. The remaining 12 tumour-bearing mice were imaged in groups of 3 to establish the quantitative accuracy of PET data using ex vivo gamma counting as the reference. Finally, a dynamic scan was performed in three mice simultaneously after the injection of (68)Ga-ethylenediaminetetraacetic acid (EDTA).

RESULTS

For typical lesion sizes of 7-8 mm phantom experiments indicated RCs of 0.42 and 0.76 for ordered subsets expectation maximization (OSEM) and PSF reconstruction, respectively. For PSF reconstruction, SOR(air) and SOR(water) were 5.3 and 7.5%, respectively. A strong correlation (r (2) = 0.97, p < 0.0001) between quantitative data obtained in mice imaged alone and simultaneously in a group of three was found following PSF reconstruction. The correlation between ex vivo counting and PET/CT data was better with PSF reconstruction (r (2) = 0.98; slope = 0.89, p < 0.0001) than without (r (2) = 0.96; slope = 0.62, p < 0.001). Valid time-activity curves of the blood pool, kidneys and bladder could be derived from (68)Ga-EDTA dynamic acquisition.

CONCLUSION

New generation clinical PET/CT can be used for simultaneous imaging of multiple small animals in experiments requiring high throughput and where a dedicated small animal PET system is not available.

Quantification of mouse pulmonary cancer models by microcomputed tomography imaging

The advances in preclinical cancer models, including orthotopic implantation models or genetically engineered mouse models of cancer, enable pursuing the molecular mechanism of cancer disease that might mimic genetic and biological processes in humans. Lung cancer is the major cause of cancer deaths; therefore, the treatment and prevention of lung cancer are expected to be improved by a better understanding of the complex mechanism of disease. In this study, we have examined the quantification of two distinct mouse lung cancer models by utilizing imaging modalities for monitoring tumor progression and drug efficacy evaluation. The utility of microcomputed tomography (micro-CT) for real-time/non-invasive monitoring of lung cancer progression has been confirmed by combining bioluminescent imaging and histopathological analyses. Further, we have developed a more clinically relevant lung cancer model by utilizing K-ras(LSL-G12D)/p53(LSL-R270H) mutant mice. Using micro-CT imaging, we monitored the development and progression of solitary lung tumor in K-ras(LSL-G12D)/p53(LSL-R270H) mutant mouse, and further demonstrated tumor growth inhibition by anticancer drug treatment. These results clearly indicate that imaging-guided evaluation of more clinically relevant tumor models would improve the process of new drug discovery and increase the probability of success in subsequent clinical studies.

Metastatic melanoma imaging with an (111)In-labeled lactam bridge-cyclized alpha-melanocyte-stimulating hormone peptide

INTRODUCTION

The purpose of this study was to examine whether a novel lactam bridge-cyclized (111)In-labeled 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-Gly-Glu-c[Lys-Nle-Glu-His-d-Phe-Arg-Trp-Gly-Arg-Pro-Val-Asp] {DOTA-GlyGlu-CycMSH} could be an effective imaging probe for metastatic melanoma detection.

METHODS

(111)In-DOTA-GlyGlu-CycMSH was prepared and purified by reverse-phase high-performance liquid chromatography (RP-HPLC). The internalization and efflux of (111)In-DOTA-GlyGlu-CycMSH were examined in B16/F10 melanoma cells. The biodistribution of (111)In-DOTA-GlyGlu-CycMSH was determined in B16/F10 pulmonary metastatic melanoma-bearing and normal C57 mice. Pulmonary metastatic melanoma imaging was performed by small-animal single-photon emission computed tomography (SPECT)/CT (Nano-SPECT/CT) using (111)In-DOTA-GlyGlu-CycMSH as an imaging probe and compared with 2-[(18)F]fluoro-2-deoxy-d-glucose ([(18)F]FDG) positron emission tomography (PET) imaging.

RESULTS

(111)In-DOTA-GlyGlu-CycMSH was readily prepared with greater than 95% radiolabeling yield. (111)In-DOTA-GlyGlu-CycMSH displayed rapid internalization and extended efflux in B16/F10 cells. (111)In-DOTA-GlyGlu-CycMSH exhibited significantly (P<.05) higher uptakes (2.00+/-0.74%ID/g at 2 h post-injection and 1.83+/-0.12%ID/g at 4 h post-injection) in metastatic melanoma-bearing lung than that in normal lung (0.08+/-0.08%ID/g and 0.05+/-0.05%ID/g at 2 and 4 h post-injection, respectively). The activity accumulation in normal organs was low (<0.5%ID/g) except for the kidneys 2 and 4 h post-injection. B16/F10 pulmonary melanoma metastases were clearly visualized with (111)In-DOTA-GlyGlu-CycMSH 2 h post-injection rather than with [(18)F]FDG 1 h post-injection.

CONCLUSIONS

(111)In-DOTA-GlyGlu-CycMSH exhibited favorable metastatic melanoma-targeting and -imaging properties, highlighting its potential as an effective imaging probe for metastatic melanoma detection.

Multimodality imaging of TGFbeta signaling in breast cancer metastases

The skeleton is a preferred site for breast cancer metastasis. We have developed a multimodality imaging approach to monitor the transforming growth factor beta (TGFbeta) signaling pathway in bone metastases, sequentially over time in the same animal. As model systems, two MDA-MB-231 breast cancer cells lines with different metastatic tropisms, SCP2 and SCP3, were transduced with constitutive and TGFbeta-inducible reporter genes and were tested in vitro and in living animals. The sites and expansion of metastases were visualized by bioluminescence imaging using a constitutive firefly luciferase reporter, while TGFbeta signaling in metastases was monitored by microPET imaging of HSV1-TK/GFP expression with [(18)F]FEAU and by a more sensitive and cost-effective bioluminescence reporter, based on nonsecreted Gaussia luciferase. Concurrent and sequential imaging of metastases in the same animals provided insight into the location and progression of metastases, and the timing and course of TGFbeta signaling. The anticipated and newly observed differences in the imaging of tumors from two related cell lines have demonstrated that TGFbeta signal transduction pathway activity can be noninvasively imaged with high sensitivity and reproducibility, thereby providing the opportunity for an assessment of novel treatments that target TGFbeta signaling.

TLD assessment of mouse dosimetry during microCT imaging

Advances in laboratory animal imaging have provided new resources for noninvasive biomedical research. Among these technologies is microcomputed tomography (microCT) which is widely used to obtain high resolution anatomic images of small animals. Because microCT utilizes ionizing radiation for image formation, radiation exposure during imaging is a concern. The objective of this study was to quantify the radiation dose delivered during a standard microCT scan. Radiation dose was measured using thermoluminescent dosimeters (TLDs), which were irradiated employing an 80 kVp x-ray source, with 0.5 mm A1 filtration and a total of 54 mA s for a full 360 deg rotation of the unit. The TLD data were validated using a 3.2 cm3 CT ion chamber probe. TLD results showed a single microCT scan air kerma of 78.0 +/- 5.0 mGy when using a poly(methylmethacrylate) (PMMA) anesthesia support module and an air kerma of 92.0 +/- 6.0 mGy without the use of the anesthesia module. The validation CT ion chamber study provided a measured radiation air kerma of 81.0 +/- 4.0 mGy and 97.0 +/- 5.0 mGy with and without the PMMA anesthesia module, respectively. Internal TLD analysis demonstrated an average mouse organ radiation absorbed dose of 76.0 +/- 5.0 mGy. The author's results have defined x-ray exposure for a routine microCT study which must be taken into consideration when performing serial molecular imaging studies involving the microCT imaging modality.

Local loperamide inhibits thermal hyperalgesia but not mechanical allodynia induced by intratibial inoculation of melanoma cells in mice

The stimulation of peripheral opioid receptors counteracts thermal hyperalgesia produced by the intratibial inoculation of NCTC 2472 cells in mice, through the activation of the nitric oxide/cGMP/ATP-sensitive K+-channels (NO/cGMP/K(+) (ATP)) cascade (Menéndez et al. 2007, Neuropharmacology 53:71-80). We aimed to elucidate whether this peripheral opioid antihyperalgesic effect is exclusive to this model or might also occur in other types of bone neoplastic processes. In C57BL/6 mice intratibially inoculated with B16-F10 melanoma cells, the progressive tumoral damage was accompanied by the establishment of thermal hyperalgesia (unilateral hot plate test) and mechanical allodynia (von Frey test). Intraplantar administration of loperamide (15 microg, 30 min before) inhibited thermal hyperalgesia, but did not modify the intense mechanical allodynia. The fact that the coadministration of naloxone-methiodide (5 microg) completely suppressed the thermal antihyperalgesic effect induced by loperamide indicates its production through the stimulation of peripheral opioid receptors. Furthermore, its prevention by the coadministration of the non-selective inhibitor of the NO synthase, N(G)-monomethyl-L-arginine (L-NMMA, 10 microg), the selective inhibitor of neural NOS, N-omega-propyl-L-arginine (1-10 microg), or the K+ (ATP) channel blocker, glibenclamide (10 microg) demonstrated the involvement of the NO/cGMP/K(+) (ATP) pathway in the antihyperalgesic effect induced by loperamide. Overall, the present results show that the intratibial inoculation of B16-F10 cells to C57BL/6 mice evokes thermal hyperalgesia and mechanical allodynia and that, as occurred in the osteosarcoma model, the stimulation of peripheral opioid receptors is not effective in modifying neoplastic allodynia but completely inhibits thermal hyperalgesia through the activation of the NO/cGMP/K+ (ATP) cascade.

Micro-CT imaging with a hepatocyte-selective contrast agent for detecting liver metastasis in living mice

RATIONALE AND OBJECTIVES

Micro-computed tomography (CT) is a important tool for longitudinal imaging of tumor development. The detection and monitoring of tumors in the liver in live animals using micro-CT is challenging. We evaluated the feasibility of high-resolution micro-CT enhanced with a hepatocyte-selective contrast agent for detecting liver metastases in a live murine model.

MATERIALS AND METHODS

Hepatic metastases were induced in 10 BALB/C mice. Two mice each were randomly selected on days 3, 5, 7, 10, and 13 after CT26 colon adenocarcinoma cells were injected into the portal vein; micro-CT imaging was performed at 10 minutes and 4 hours after intravenous administration of a hepatocyte-selective contrast agent at a dose of 0.4 mL/mouse. The attenuation values of the normal liver and the tumors were obtained. The number of metastases was counted and their sizes were measured on the micro-CT images. Gross or histopathologic evaluation was performed for correlating the liver tumors with the micro-CT images.

RESULTS

A total of 74 separate tumor sites larger than 300 microm in diameter were detected on pathologic examination of the mice that were sacrificed 7 days after cell injection. On micro-CT, 66 of 74 tumors were detected (83.8%). The smallest tumor detected on micro-CT was 300 microm. There were eight false-negative readings on micro-CT. The sizes of the individual liver metastases measured by micro-CT and on the excised specimen were highly correlated (P < .001). The correlation between the CT scan measurement and the actual measurement was r = 0.8354 (P < .0001).

CONCLUSIONS

High-resolution micro-CT enhanced with a hepatocyte-selective contrast agent can be a promising tool for detecting liver metastases in a live murine model.

Periodic analysis of urethane-induced pulmonary tumors in living A/J mice by respiration-gated X-ray microcomputed tomography

X-ray microcomputed tomography (micro-CT) with a respiratory gating system is a useful non-invasive approach to evaluate lung tumor development in living animal models. Here micro-CT was applied for the detection of lung lesions induced by a single intraperitoneal injection (250 mg/kg) of urethane in male A/J mice, at 2-week intervals from 10 to 30 weeks after carcinogen exposure. In micro-CT cross sections, lung tumor images were easily distinguished from surrounding non-tumorous tissues, the smallest detected tumor being approximately 0.5 mm in diameter. All of the urethane-treated mice (n = 15) developed lung tumors and the number of tumors developed in each mouse was 8.6 +/- 3.9. Six tumors, determined histopathologically to be adenocarcinomas, were detected, growing at different rates during the experimental period. The most aggressive carcinoma, increasing in diameter from 0.9 to 3.5 mm within 8 weeks, was a solid-type nodule with a clear tumor margin on the micro-CT imaging. Other tumors, histopathologically adenomas, grew slowly or moderately. The results provide evidence that micro-CT is a useful non-invasive imaging approach for evaluating the characteristics and growth of lung tumors in mice.

In vivo small-animal imaging using micro-CT and digital subtraction angiography

Small-animal imaging has a critical role in phenotyping, drug discovery and in providing a basic understanding of mechanisms of disease. Translating imaging methods from humans to small animals is not an easy task. The purpose of this work is to review in vivo x-ray based small-animal imaging, with a focus on in vivo micro-computed tomography (micro-CT) and digital subtraction angiography (DSA). We present the principles, technologies, image quality parameters and types of applications. We show that both methods can be used not only to provide morphological, but also functional information, such as cardiac function estimation or perfusion. Compared to other modalities, x-ray based imaging is usually regarded as being able to provide higher throughput at lower cost and adequate resolution. The limitations are usually associated with the relatively poor contrast mechanisms and potential radiation damage due to ionizing radiation, although the use of contrast agents and careful design of studies can address these limitations. We hope that the information will effectively address how x-ray based imaging can be exploited for successful in vivo preclinical imaging.

Predicting and monitoring colitis development in mice by micro-computed tomography

BACKGROUND

Computed tomography (CT) has been developed as a tool for monitoring human inflammatory bowel disease (IBD). The aim of this study was to evaluate colon wall thickness as a noninvasive marker in the dextran sodium sulfate (DSS) mouse model of colitis using micro-CT.

METHODS

Mice were examined by micro-CT 1, 2, or 4 times between day 0 (d0) and d26 after induction of colitis to document the kinetics of changes in colon wall thickness and its relation to colitis development.

RESULTS

DSS-treated mice displayed a significantly thicker colon wall at all timepoints (days 5, 8, 12, 19, and 26) investigated compared to healthy controls. Colon wall thickness showed a good correlation to the macroscopic grading of colitis (r = 0.81). The increase in colon wall thickness occurred mainly during the acute phase of colitis (between days 5 and 12) and did not progress much further in the chronic phase of colitis (d26). Colon wall thickness at d26 was thereby predicted by measurements at d12. All mice did not respond equally to DSS and this difference was manifest during the first 2 weeks of colitis, providing an important tool in stratifying responders from nonresponders.

CONCLUSIONS

While the potential impact of handling and anesthesia should be considered on repeated micro-CT, irradiation exposure during repeated micro-CT did not affect the development of colitis. Thus, the results suggest that micro-CT can be used for monitoring and prediction of the inflammatory response in mouse colitis in future therapeutic studies.

Flat-panel detector-based volume computed tomography: a novel 3D imaging technique to monitor osteolytic bone lesions in a mouse tumor metastasis model

Skeletal metastasis is an important cause of mortality in patients with breast cancer. Hence, animal models, in combination with various imaging techniques, are in high demand for preclinical assessment of novel therapies. We evaluated the applicability of flat-panel volume computed tomography (fpVCT) to noninvasive detection of osteolytic bone metastases that develop in severe immunodeficient mice after intracardial injection of MDA-MB-231 breast cancer cells. A single fpVCT scan at 200-microm isotropic resolution was employed to detect osteolysis within the entire skeleton. Osteolytic lesions identified by fpVCT correlated with Faxitron X-ray analysis and were subsequently confirmed by histopathological examination. Isotropic three-dimensional image data sets obtained by fpVCT were the basis for the precise visualization of the extent of the lesion within the cortical bone and for the measurement of bone loss. Furthermore, fpVCT imaging allows continuous monitoring of growth kinetics for each metastatic site and visualization of lesions in more complex regions of the skeleton, such as the skull. Our findings suggest that fpVCT is a powerful tool that can be used to monitor the occurrence and progression of osteolytic lesions in vivo and can be further developed to monitor responses to antimetastatic therapies over the course of the disease.

Serum osteopontin, an enhancer of tumor metastasis to bone, promotes B16 melanoma cell migration

Tumor malignancy is associated with several features such as proliferation ability and frequency of metastasis. Since tumor metastasis shortens patients' lifetime, establishment of therapy for anti-metastasis is very important. Osteopontin (OPN), which abundantly expressed in bone matrix, is involved in cell adhesion, migration, extracellular matrix (ECM) invasion and cell proliferation via interaction with its receptor, that is, alphavbeta3 integrin. OPN is believed to be a positive regulator of tumor metastasis in vivo. However, how OPN regulates metastasis is largely unknown. Here, we explore the role of OPN in cell migration. Serum from wild-type mice induced cell migration of B16 melanoma cells, while serum from OPN-deficient mouse suppressed this event. The presence of recombinant OPN significantly enhanced cell migration compared to albumin containing medium. OPN-induced cell migration was suppressed by inhibiting the ERK/MAPK pathway indicating that OPN-induced cell migration depends on this pathway. Overexpression of OPN in these cancer cells per se promoted cell proliferation and tended to increase B16 cell migration suggesting that OPN promotes bone metastasis by playing dual roles both in host microenvironment and in tumor cell itself. In conclusion, the elevated OPN expression in host tissue and tumor cell itself promotes tumor cell migration reading to tumor metastasis, suggesting that neutralization of OPN-induced signal might be effective in suppression of tumor metastasis.

Small Animal Absorbed Radiation Dose from Serial Micro-Computed Tomography Imaging

PURPOSE

To determine the radiation dose to mouse cancer xenografts from serial micro-computed tomography (CT) examinations.

PROCEDURES

A nude mouse with a 15-mm subcutaneous pancreatic cancer xenograft in the rightflank was used. Radiation exposure to the subcutaneous tumor and the mouse pancreas (to simulate an orthotopic pancreatic tumor model) was measured using lithium fluoride thermoluminescent dosimeters. Ultrafast micro-CT was performed using 80 kVp, 0.26 mA, 0.156 mm slice thickness, 256 slices, 0.7 mm Al filtration, and 60-second image acquisition time (15 mA second). Micro-CT imaging acquisitions were repeated four times.

RESULTS

We measured consistently low tumor doses (0.014 to 0.02 Gy; average=0.017 Gy) per scan. Orthotopic doses in the region of the pancreas were also consistently low (0.014 to 0.018 Gy; average=0.016 Gy) per scan.

CONCLUSIONS

Radiation doses delivered during ultrafast micro-CT serial imaging in the mouse are low and are likely below the threshold to affect tumor growth.