[Imaging in the acute abdomen-part 2 : Case examples of frequent organ-specific causes: gastrointestinal tract and urogenital system]

The acute abdomen is a potentially life-threatening condition and requires a rapid diagnosis. After clinical inspection and in cases with unclear ultrasound findings or unclear serious symptoms computed tomography (CT) and in pregnant women and children magnetic resonance imaging (MRI) is usually necessary. This second part of "Imaging in the acute abdomen" focuses on frequent organ specific causes of the gastrointestinal tract and the urogenital system.

[Imaging in the acute abdomen - part 1 : Case examples of frequent organ-specific causes: liver, gallbladder, pancreas, spleen and vessels]

The acute abdomen is characterized by acute abdominal pain with defensive muscular tension, can be triggered by a variety of diseases and sometimes represents a life-threatening condition. After clinical inspection, in most cases dedicated imaging should be performed immediately. The frequently causal appendicitis and cholecystitis can mostly be diagnosed with ultrasound. In other cases with unclear ultrasound findings or unclear severe symptoms, computer tomography (CT) is usually necessary without delay. In contrast, magnetic resonance imaging (MRI) is predominantly indicated in pregnant women and children with unclear ultrasound findings. Thus, the radiologist is an important gatekeeper in the diagnostics of acute abdomen. The radiologist should therefore be familiar with the correct imaging indications, the frequent and rare causes as well as the corresponding morphological imaging characteristics.

Multimodal Targeted Nanoparticle-Based Delivery System for Pancreatic Tumor Imaging in Cellular and Animal Models

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC), which ranks forth on the cancer-related death statistics still is both a diagnostic and a therapeutic challenge. Adenocarcinoma of the exocrine human pancreas originates in most instances from malignant transformation of ductal epithelial cells, alternatively by Acinar-Ductal Metaplasia (ADM). RA96 antibody targets to a mucin M1, according to the more recent nomenclature MUC5AC, an extracellular matrix component excreted by PDAC cells. In this study, we tested the usability of multimodal nanoparticle carrying covalently coupled RA96 Fab fragments for pancreatic tumor imaging.

METHODS

In order to make and evaluate a novel, better targeting, theranostic nanoparticle, iron nanoparticles and the optical dye indocyanin green (ICG) were encapsulated into the cationic sphingomyelin (SM) consisting liposomes. RA-96 Fab fragment was conjugated to the liposomal surface of the nanoparticle to increase tumor homing ability. ICG and iron nanoparticle-encapsulated liposomes were studied in vitro with cells and (i) their visibility in magnetic resonance imaging (MRI), (ii) optical, (iii) Magnetic particle spectroscopy (MPS) and (iv) photoacoustic settings was tested in vitro and also in in vivo models. The targeting ability and MRI and photoacoustic visibility of the RA-96-nanoparticles were first tested in vitro cell models where cell binding and internalization was studied. In in vivo experiments liposomal nanoparticles were injected into a tail vain using an orthotopic pancreatic tumor xenograft model and subcutaneous pancreas cancer cell xenografts bearing mice to determine in vivo targeting abilities of RA-96-conjugated liposomes.

RESULTS

Multimodal liposomes could be detected by MRI, MPS and by photoacoustic imaging in addition to optical imaging showing a wide range of imaging utility. The fluorescent imaging of ICG in pancreatic tumor cells Panc89 and Capan-2 revealed increased association of ICG-encapsulated liposomes carrying RA-96 Fab fragments in vitro compared to the control liposomes without covalently linked RA-96. Fluorescent molecular tomography (FMT) studies showed increased accumulation of the RA96-targeted nanoparticles in the tumor area compared to non-targeted controls in vivo. Similar accumulation in the tumor sites could be seen with liposomal ferric particles in MRI. Fluorescent tumor signal was confirmed by using an intraoperative fluorescent imaging system which showed fluorescent labeling of pancreatic tumors.

CONCLUSION

These results suggest that RA-96-targeted liposomes encapsulating ICG and iron nanoparticles can be used to image pancreatic tumors with a variety of optical and magnetic imaging techniques. Additionally, they might be a suitable drug delivery tool to improve treatment of PDAC patients.

ATM activity in T cells is critical for immune surveillance of lymphoma in vivo

The proximal DNA damage response kinase ATM is frequently inactivated in human malignancies. Germline mutations in the ATM gene cause Ataxia-telangiectasia (A-T), characterized by cerebellar ataxia and cancer predisposition. Whether ATM deficiency impacts on tumor initiation or also on the maintenance of the malignant state is unclear. Here, we show that Atm reactivation in initially Atm-deficient B- and T cell lymphomas induces tumor regression. We further find a reduced T cell abundance in B cell lymphomas from Atm-defective mice and A-T patients. Using T cell-specific Atm-knockout models, as well as allogeneic transplantation experiments, we pinpoint impaired immune surveillance as a contributor to cancer predisposition and development. Moreover, we demonstrate that Atm-deficient T cells display impaired proliferation capacity upon stimulation, due to replication stress. Altogether, our data indicate that T cell-specific restoration of ATM activity or allogeneic hematopoietic stem cell transplantation may prevent lymphomagenesis in A-T patients.

Volumetric analysis of MRONJ lesions by semiautomatic segmentation of CBCT images

PURPOSE

The purpose of this study was to evaluate potential differences in volumes of areas of osteolysis caused by medication-related osteonecrosis of the jaw (MRONJ) between the upper and lower jaw. We aim to analyze the clinical relevance of volumetric measurement of osteolytic lesions for surgical planning of MRONJ patients.

METHODS

Sixty-seven patients who were clinically and histopathologically diagnosed with MRONJ were retrospectively included in this study. Cone beam computed tomography (CBCT) images were evaluated according to localization, affected anatomical structures, and volumetric measurement of osteolytic lesions caused by MRONJ in appliance of CBCT datasets by using ITK-SNAP.

RESULTS

The most frequently affected localization is the mandible, whereas female patients show significantly more often lesions of the maxilla. The cortical bone was predominantly affected. Furthermore, the affection of teeth, sinus floor, inferior alveolar nerve canal, or even a pathological fracture of the mandible are infrequently existing. The volumetric measurements revealed a statistically significant greater absolute osteolysis volume in males.

CONCLUSIONS

Image analysis and volumetric measurements of osteolytic lesions of MRONJ patients is a helpful tool to further understand the clinical appearance and identify compromised anatomic landmarks. Volumetric analysis aids in pre-surgical planning and visualizes the individual extent of the disease for each patient.

Magnetic Resonance-Guided High-Intensity Focused Ultrasound (MR-HIFU): Overview of Emerging Applications (Part 2)

BACKGROUND

 High-intensity focused ultrasound (HIFU) allows noninvasive heating of deep-seated tissues. Guidance under magnetic resonance imaging (MR-HIFU) offers spatial targeting based on anatomical MR images as well as MR-based near-real-time temperature maps. Temperature feedback allows delivery of a well-defined thermal dose enabling new applications such as the ablation of malignant tissue.

METHODS

 Peer-reviewed publications on MR-HIFU were studied and are summarized in this review. Literature was restricted to applications in oncology.

RESULTS

 Several MR-HIFU-based applications for the treatment of malignant diseases are currently part of clinical trials or translational research. Recent trials regarding the treatment of prostate cancer with MR-HIFU have already shown this to be a safe and patient-friendly method. For the treatment of breast cancer and malignancies within abdominal organs, MR-HIFU has been applied so far only in proof of concept studies.

CONCLUSION

 MR-HIFU is currently being investigated for the ablative treatment of malignant tissue in a variety of oncological applications. For example, the transrectal as well as transurethral ablation of prostate cancer using MR-HIFU was shown to be a patient-friendly, safe alternative to other local treatment options with low side effects.

KEY POINTS

  · MR guidance offers high soft tissue contrast for treatment planning, near-real-time temperature monitoring, and post-interventional therapy evaluation.. · Special HIFU transducers and technological solutions are available for the treatment of e. g. prostate cancer, breast cancer or abdominal malignancies..

CITATION FORMAT

· Siedek F, Yeo SY, Heijman E et al. MR-Guided High-Intensity Focused Ultrasound (MR-HIFU): Overview of Emerging Applications (Part 2). Fortschr Röntgenstr 2019; 191: 531 - 539.

Magnetic Resonance-Guided High-Intensity Focused Ultrasound (MR-HIFU): Technical Background and Overview of Current Clinical Applications (Part 1)

BACKGROUND

 Extracorporeal high-intensity focused ultrasound (HIFU) is a promising method for the noninvasive thermal ablation of benign and malignant tissue. Current HIFU treatments are performed under ultrasound (US-HIFU) or magnetic resonance (MR-HIFU) image guidance offering integrated therapy planning, real-time control (spatial and temperature guidance) and evaluation.

METHODS

 This review is based on publications in peer-reviewed journals addressing thermal ablation using HIFU and includes our own clinical results as well. The technical background of HIFU is explained with an emphasis on MR-HIFU applications. A brief overview of the most commonly performed CE-approved clinical applications for MR-HIFU is given.

RESULTS

 Over the last decade, several HIFU-based applications have received clinical approval in various countries. In particular, MR-HIFU is now approved for the clinical treatment of uterine fibroids, palliation of bone pain, ablation of the prostate and treatment of essential tremor as a first neurological application.

CONCLUSION

 MR-HIFU is a patient-friendly noninvasive method for thermal ablation which has received clinical approval for several applications. Overall, clinical data demonstrate treatment efficacy, safety and cost efficiency.

KEY POINTS

  · HIFU is a promising technique for noninvasive thermal ablation of tissue.. · HIFU is typically performed under image guidance using either diagnostic ultrasound (US-HIFU) or MRI (MR-HIFU).. · The preferred image guidance modality depends on the application.. · MR guidance offers improved soft-tissue contrast for treatment planning, near real-time and noninvasive temperature monitoring and post-interventional therapy evaluation.. · MR-HIFU is CE-approved for treatment of uterine fibroids, alleviation of bone pain, prostate tissue ablation and treatment of essential tremor..

CITATION FORMAT

· Siedek F, Yeo S, Heijman E et al. Magnetic Resonance-Guided High-Intensity Focused Ultrasound (MR-HIFU): Technical Background and Overview of Current Clinical Applications (Part 1). Fortschr Röntgenstr 2019; 191: 522 - 530.

The novel TRAIL-receptor agonist APG350 exerts superior therapeutic activity in pancreatic cancer cells

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has raised attention as a novel anticancer therapeutic as it induces apoptosis preferentially in tumor cells. However, first-generation TRAIL-receptor agonists (TRAs), comprising recombinant TRAIL and agonistic receptor-specific antibodies, have not demonstrated anticancer activity in clinical studies. In fact, cancer cells are often resistant to conventional TRAs. Therefore, in addition to TRAIL-sensitizing strategies, next-generation TRAs with superior apoptotic activity are warranted. APG350 is a novel, highly potent TRAIL-receptor agonist with a hexavalent binding mode allowing the clustering of six TRAIL-receptors per drug molecule. Here we report on preclinical in vitro and in vivo studies testing the activity of APG350 on pancreatic ductal adenocarcinoma (PDAC) cells. We found that APG350 potently induced apoptosis of Colo357, PancTuI and Panc89 cells in vitro. In addition, APG350 treatment activated non-canonical TRAIL signaling pathways (MAPK, p38, JNK, ERK1/ERK2 and NF-κB) and induced the secretion of IL-8. Stable overexpression of Bcl-xL inhibited APG350-induced cell death and augmented activation of non-canonical pathways. Intriguingly, pre-treatment of Bcl-xL-overexpressing cells with the BH3-mimic Navitoclax restored their sensitivity to APG350. To study the effects of APG350 on PDAC cells in vivo, we applied two different orthotopic xenotransplantation mouse models, with and without primary tumor resection, representing adjuvant and palliative treatment regimes, respectively. APG350 treatment of established tumors (palliative treatment) significantly reduced tumor burden. These effects, however, were not seen in tumors with enforced overexpression of Bcl-xL. Upon primary tumor resection and subsequent APG350 treatment (adjuvant therapy), APG350 limited recurrent tumor growth and metastases. Importantly, therapeutic efficacy of APG350 treatment was more effective compared with treatment with soluble TRAIL in both models. In conclusion, APG350 represents a promising next-generation TRA for the treatment of PDAC. Moreover, our results suggest that combining APG350 with Navitoclax might be a succesfull strategy for cancers harboring mitochondrial apoptosis resistance.

Intra-individual comparison between abdominal virtual mono-energetic spectral and conventional images using a novel spectral detector CT

OBJECTIVES

To quantitatively and qualitatively assess abdominal arterial and venous phase contrast-enhanced spectral detector computed tomography (SDCT) virtual mono-energetic (MonoE) datasets in comparison to conventional CT reconstructions provided by the same system.

MATERIALS AND METHODS

Conventional and MonoE images at 40-120 kilo-electron volt (keV) levels with a 10 keV increment as well as 160 and 200 keV were reconstructed in abdominal SDCT datasets of 55 patients. Attenuation, image noise, and contrast- / signal-to-noise ratios (CNR, SNR) of vessels and solid organs were compared between MonoE and conventional reconstructions. Two readers assessed contrast conditions, detail visualization, overall image quality and subjective image noise with both, fixed and adjustable window settings.

RESULTS

Attenuation, CNR and SNR of vessels and solid organs showed a stepwise increase from high to low keV reconstructions in both contrast phases while image noise stayed stable at low keV MonoE reconstruction levels. Highest levels were found at 40 keV MonoE reconstruction (p<0.001), respectively. Solid abdominal organs showed a stepwise decrease from low to high energy levels in regard to attenuation, CNR and SNR with significantly higher values at 40 and 50 keV, compared to conventional images. The 70 keV MonoE was comparable to conventional poly-energetic reconstruction (p≥0.99). Subjective analysis displayed best image quality for the 70 keV MonoE reconstruction level in both phases at fixed standard window presets and at 40 keV if window settings could be adjusted.

CONCLUSION

SDCT derived low keV MonoE showed markedly increased CNR and SNR values due to constantly low image noise values over the whole energy spectrum from 40 to 200 keV.

IL-6 trans-signaling is essential for the development of hepatocellular carcinoma in mice

Hepatocellular carcinoma (HCC) is one of the most frequent tumors worldwide with rising incidence. The inflammatory cytokine, interleukin-6 (IL-6), is a critical mediator of HCC development. It can signal through two distinct pathways: the IL-6 classic and the IL-6 trans-signaling pathway. Whereas IL-6 classic signaling is important for innate and acquired immunity, IL-6 trans-signaling has been linked to accelerated liver regeneration and several chronic inflammatory pathologies. However, its implication in liver tumorigenesis has not been addressed yet. Here, we show that IL-6 trans-signaling, but not IL-6 classic signaling, is essential to promote hepatocellular carcinogenesis by two mechanisms: First, it prevents DNA-damage-induced hepatocyte apoptosis through suppression of p53 and enhances β-catenin activation and tumor proliferation. Second, IL-6 trans-signaling directly induces endothelial cell proliferation to promote tumor angiogenesis. Consequently, soluble gp130 fused to Fc transgenic mice lacking IL-6 trans-signaling are largely protected from tumor formation in a diethylnitrosamine/3,3',5,5'-tetrachloro-1,4-bis(pyridyloxy)benzene model of HCC.

CONCLUSION

IL-6 trans-signaling, and not IL-6 classic signaling, is mandatory for development of hepatocellular carcinogenesis. Therefore, specific inhibition of IL-6 trans-signaling, rather than total inhibition of IL-6 signaling, is sufficient to blunt tumor initiation and impair tumor progression without compromising IL-6 classic signaling-driven protective immune responses. (Hepatology 2017;65:89-103).

Fractal Dimension of Tumor Microvasculature by DCE-US: Preliminary Study in Mice

Neoangiogenesis, which results in the formation of an irregular network of microvessels, plays a fundamental role in the growth of several types of cancer. Characterization of microvascular architecture has therefore gained increasing attention for cancer diagnosis, treatment monitoring and evaluation of new drugs. However, this characterization requires immunohistologic analysis of the resected tumors. Currently, dynamic contrast-enhanced ultrasound imaging (DCE-US) provides new options for minimally invasive investigation of the microvasculature by analysis of ultrasound contrast agent (UCA) transport kinetics. In this article, we propose a different method of analyzing UCA concentration that is based on the spatial distribution of blood flow. The well-known concept of Mandelbrot allows vascular networks to be interpreted as fractal objects related to the regional blood flow distribution and characterized by their fractal dimension (FD). To test this hypothesis, the fractal dimension of parametric maps reflecting blood flow, such as UCA wash-in rate and peak enhancement, was derived for areas representing different microvascular architectures. To this end, subcutaneous xenograft models of DU-145 and PC-3 prostate-cancer lines in mice, which show marked differences in microvessel density spatial distribution inside the tumor, were employed to test the ability of DCE-US FD analysis to differentiate between the two models. For validation purposes, the method was compared with immunohistologic results and UCA dispersion maps, which reflect the geometric properties of microvascular architecture. The results showed good agreement with the immunohistologic analysis, and the FD analysis of UCA wash-in rate and peak enhancement maps was able to differentiate between the two xenograft models (p < 0.05).

Increased survival rate by local release of diclofenac in a murine model of recurrent oral carcinoma

Despite aggressive treatment with radiation and combination chemotherapy following tumor resection, the 5-year survival rate for patients with head and neck cancer is at best only 50%. In this study, we examined the therapeutic potential of localized release of diclofenac from electrospun nanofibers generated from poly(D,L-lactide-co-glycolide) polymer. Diclofenac was chosen since anti-inflammatory agents that inhibit cyclooxygenase have shown great potential in their ability to directly inhibit tumor growth as well as suppress inflammation-mediated tumor growth. A mouse resection model of oral carcinoma was developed by establishing tumor growth in the oral cavity by ultrasound-guided injection of 1 million SCC-9 cells in the floor of the mouth. Following resection, mice were allocated into four groups with the following treatment: 1) no treatment, 2) implanted scaffolds without diclofenac, 3) implanted scaffolds loaded with diclofenac, and 4) diclofenac given orally. Small animal ultrasound and magnetic resonance imaging were utilized for longitudinal determination of tumor recurrence. At the end of 7 weeks following tumor resection, 33% of mice with diclofenac-loaded scaffolds had a recurrent tumor, in comparison to 90%–100% of the mice in the other three groups. At this time point, mice with diclofenac-releasing scaffolds showed 89% survival rate, while the other groups showed survival rates of 10%–25%. Immunohistochemical staining of recurrent tumors revealed a near 10-fold decrease in the proliferation marker Ki-67 in the tumors derived from mice with diclofenac-releasing scaffolds. In summary, the local application of diclofenac in an orthotopic mouse tumor resection model of oral cancer reduced tumor recurrence with significant improvement in survival over a 7-week study period following tumor resection. Local drug release of anti-inflammatory agents should be investigated as a therapeutic option in the prevention of tumor recurrence in oral squamous carcinoma.

Laser scoop desobliteration: a method for minimally invasive remote recanalization of chronically occluded superficial femoral arteries

Stenosis and occlusion of the superficial femoral artery (SFA) are most common in arterial occlusive disease. There are numerous interventional, surgical, and combined approaches to reconstitute maximum blood supply to the lower limb; however, despite intense clinical research, the long-term success rates are still poor. We present the first results with a catheter prototype for laser-based minimal invasive endarterectomy, called laser scoop desobliteration (LSD). The tip of a glass fiber containing a catheter was modified with a spatula head design and connected to an ultraviolet laser. It was tested in cadavers fixed with the Thiel embalming technique preserving tissue consistency, flexibility, and plasticity. After longitudinal arteriotomy of the SFA, a circular dissection between media and adventitia was performed. Then the LSD catheter was inserted and propagated with a progress of 1 mm∕s. Afterward, the atheroma core, which showed a plain surface without substantial attaching tissue debris, was removed. Histological examination of the vessel wall showed that the dissection was performed at the media/adventitia interface. In summary, the constructed LSD catheter allowed a rapid and easy way to perform an endarterectomy, thereby offering an innovative approach in the treatment of chronic occluded SFA.

Inhibition of IL-6 signaling significantly reduces primary tumor growth and recurrencies in orthotopic xenograft models of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is one of the most fatal human tumors, with radical surgical resection as the only curative treatment option. However, resection is only possible in a small fraction of patients, and about 80% of the patients develop recurrencies. PDAC development is facilitated by the cytokine interleukin-6 (IL-6), which acts via classic and trans-signaling. Both pathways are inhibited by the anti-IL-6-receptor antibody tocilizumab, whereas the fusion protein sgp130Fc specifically blocks trans-signaling. Here, we show that conservative or adjuvant therapy with both inhibitors reduces tumor growth in an orthotopic model of human Colo357 cells in SCID/bg mice. In the conservative setting, median primary tumor weight was reduced 2.4-fold for tocilizumab and 4.4-fold for sgp130Fc. sgp130Fc additionally led to a decrease in microvessel density, which was not observed with tocilizumab. In the adjuvant therapeutic setting after surgical resection of the primary tumor, treatment with tocilizumab or sgp130Fc decreased the local recurrence rate from 87.5% in the control group to 62.5 or 50%, respectively. Furthermore, the median weight of the local recurrent tumors was clearly diminished, and both inhibitors reduced the number of distant metastases. A significant reduction of tumor weight and metastases-comparable to gemcitabine treatment-was also observed with both inhibitors in another model using the poorly differentiated PancTuI cells. Our findings demonstrate the inhibition of IL-6 as a new treatment option in PDAC.

Nuclear death receptor TRAIL-R2 inhibits maturation of let-7 and promotes proliferation of pancreatic and other tumor cells

BACKGROUND & AIMS

Tumor necrosis factor-related apoptosis inducing ligand (TRAIL-R1) (TNFRSF10A) and TRAIL-R2 (TNFRSF10B) on the plasma membrane bind ligands that activate apoptotic and other signaling pathways. Cancer cells also might have TRAIL-R2 in the cytoplasm or nucleus, although little is known about its activities in these locations. We investigated the functions of nuclear TRAIL-R2 in cancer cell lines.

METHODS

Proteins that interact with TRAIL-R2 initially were identified in pancreatic cancer cells by immunoprecipitation, mass spectrometry, and immunofluorescence analyses. Findings were validated in colon, renal, lung, and breast cancer cells. Functions of TRAIL-R2 were determined from small interfering RNA knockdown, real-time polymerase chain reaction, Drosha-activity, microRNA array, proliferation, differentiation, and immunoblot experiments. We assessed the effects of TRAIL-R2 overexpression or knockdown in human pancreatic ductal adenocarcinoma (PDAC) cells and their ability to form tumors in mice. We also analyzed levels of TRAIL-R2 in sections of PDACs and non-neoplastic peritumoral ducts from patients.

RESULTS

TRAIL-R2 was found to interact with the core microprocessor components Drosha and DGCR8 and the associated regulatory proteins p68, hnRNPA1, NF45, and NF90 in nuclei of PDAC and other tumor cells. Knockdown of TRAIL-R2 increased Drosha-mediated processing of the let-7 microRNA precursor primary let-7 (resulting in increased levels of mature let-7), reduced levels of the let-7 targets (LIN28B and HMGA2), and inhibited cell proliferation. PDAC tissues from patients had higher levels of nuclear TRAIL-R2 than non-neoplastic pancreatic tissue, which correlated with increased nuclear levels of HMGA2 and poor outcomes. Knockdown of TRAIL-R2 in PDAC cells slowed their growth as orthotopic tumors in mice. Reduced nuclear levels of TRAIL-R2 in cultured pancreatic epithelial cells promoted their differentiation.

CONCLUSIONS

Nuclear TRAIL-R2 inhibits maturation of the microRNA let-7 in pancreatic cancer cell lines and increases their proliferation. Pancreatic tumor samples have increased levels of nuclear TRAIL-R2, which correlate with poor outcome of patients. These findings indicate that in the nucleus, death receptors can function as tumor promoters and might be therapeutic targets.

Lack of CCR7 expression is rate limiting for lymphatic spread of pancreatic ductal adenocarcinoma

CCR7 expression on tumor cells promotes lymphatic spread in several malignant tumors. However, a comprehensive characterization of the CCL19/CCL21-CCR7 axis in pancreatic ductal adenocarcinoma (PDAC), which is known for its high rates of lymph-node metastases, is still lacking. CCR7 mRNA and CCR7 protein were found to be expressed in spheroid cultures of all six examined PDAC cell lines. In migration assays, CCR7 expressing PDAC cells showed enhanced migration toward CCL19 and CCL21, the two ligands of CCR7. In an orthotopic nude mouse model, CCR7-transfected PT45P1 cells gave rise to significantly larger tumors and showed a higher frequency of lymph vessel invasion and lymph-node metastases than mock-transfected cells. In an analysis using quantitative real-time PCR, CCR7 showed fourfold overexpression in microdissected PDAC cells compared to normal duct cells. Moderate-to-strong immunohistochemical CCR7 expression, found in 58 of 121 well-characterized human PDACs, correlated with high rates of lymph vessel invasion. Conversely, PDACs completely lacking CCR7 expression showed only low rates of lymph vessel invasion and lymph-node metastases. The evaluation of CCL21 expression by immunofluorescence staining revealed a significant upregulation of CCL21 in peritumoral and intratumoral lymph vessels compared to lymph vessels in disease-free pancreata. In conclusion, our study revealed strong evidence that lack of CCR7 impairs the metastatic potential of PDAC. Lymph vessel invasion by CCR7 expressing PDAC cells may be additionally enhanced by upregulation of CCL21 in tumor-associated lymph vessels, representing a previously unknown factor of lymphatic spread.

Magnitude of enhanced permeability and retention effect in tumors with different phenotypes: 89Zr-albumin as a model system

Targeted nanoparticle-based technologies show increasing prevalence in radiotracer design. As a consequence, quantitative contribution of nonspecific accumulation in the target tissue, mainly governed by the enhanced permeability and retention (EPR) effect, becomes highly relevant for evaluating the specificity of these new agents. This study investigated the influence of different tumor phenotypes on the EPR effect, hypothesizing that a baseline level of uptake must be exceeded to visualize high and specific uptake of a targeted macromolecular radiotracer.

METHODS

These preliminary studies use (89)Zr-labeled mouse serum albumin ((89)Zr-desferrioxamine-mAlb) as a model radiotracer to assess uptake and retention in 3 xenograft models of human prostate cancer (CWR22rv1, DU-145, and PC-3). Experiments include PET and contrast-enhanced ultrasound imaging to assess morphology, vascularization, and radiotracer uptake; temporal ex vivo biodistribution studies to quantify radiotracer uptake over time; and histologic and autoradiographic studies to evaluate the intra- and intertumoral distribution of (89)Zr-desferrioxamine-mAlb.

RESULTS

Early uptake profiles show statistically significant but overall small differences in radiotracer uptake between different tumor phenotypes. By 20 h, nonspecific radiotracer uptake was found to be independent of tumor size and phenotype, reaching at least 5.0 percentage injected dose per gram in all 3 tumor models.

CONCLUSION

These studies suggest that minimal differences in tumor uptake exist at early time points, dependent on the tumor type. However, these differences equalize over time, reaching around 5.0 percentage injected dose per gram at 20 h after injection. These data provide strong support for the introduction of mandatory experimental controls of future macromolecular or nanoparticle-based drugs, particularly regarding the development of targeted radiotracers.

Epithelial-mesenchymal transition in Rhesus monkey embryonic stem cell colonies: a model for processes involved in gastrulation?

A characteristic feature of embryonic stem (ES) cells is their ability to give rise to differentiated cell types that are derived from all three primary germ layers. In the embryo of higher vertebrates, formation of mesoderm and definitive endoderm (gastrulation) occurs at the primitive streak through a spatially highly ordered process of cell ingression, combined with epithelial-mesenchymal transition (EMT). With respect to ES cell differentiation in vitro, however, germ layer derivative formation has not been studied in much detail, and data on any degree of spatial order that may be attained here are lacking. In the investigations to be reviewed here, rhesus monkey ES cells (line R366.4) were grown on mouse embryonic fibroblast feeder layers for up to 10 days during which time they formed multilayered disc-like colonies with an upper epithelial and a lower mesenchymal cell layer. Processes of epithelialization as well as EMT were studied by transmission electron microscopy, immunohistochemistry combined with confocal laser scanning microscopy, and marker mRNA expression (in situ hybridization, RT-PCR). It was found that under the culture conditions used most of the ES cell colonies developed transitorily a central pit where the epithelial upper layer cells underwent an EMT-like process and appeared to ingress to form the lower, mesenchymal layer, accompanied by appropriate changes of morphology and molecular markers. Similarities and differences in comparison with gastrulation/primitive streak formation in vivo are briefly discussed, as are ethical implications with respect to human ES cells. It is concluded that this rhesus ES cell colony system may be an interesting in vitro model for studies on some basic processes involved in early embryogenesis such as EMT/gastrulation and may open new ways to study the regulation of these processes experimentally in vitro in nonhuman primates.

Epithelial-mesenchymal transition in colonies of rhesus monkey embryonic stem cells: a model for processes involved in gastrulation

Rhesus monkey embryonic stem (rhES) cells were grown on mouse embryonic fibroblast (MEF) feeder layers for up to 10 days to form multilayered colonies. Within this period, stem cell colonies differentiated transiently into complex structures with a disc-like morphology. These complex colonies were characterized by morphology, immunohistochemistry, and marker mRNA expression to identify processes of epithelialization as well as epithelial-mesenchymal transition (EMT) and pattern formation. Typically, differentiated colonies were comprised of an upper and a lower ES cell layer, the former growing on top of the layer of MEF cells whereas the lower ES cell layer spread out underneath the MEF cells. Interestingly, in the central part of the colonies, a roundish pit developed. Here the feeder layer disappeared, and upper layer cells seemed to ingress and migrate through the pit downward to form the lower layer while undergoing a transition from the epithelial to the mesenchymal phenotype, which was indicated by the loss of the marker proteins E-cadherin and ZO-1 in the lower layer. In support of this, we found a concomitant 10-fold upregulation of the gene Snail2, which is a key regulator of the EMT process. Conversion of epiblast to mesoderm was also indicated by the regulated expression of the mesoderm marker Brachyury. An EMT is a characteristic process of vertebrate gastrulation. Thus, these rhES cell colonies may be an interesting model for studies on some basic processes involved in early primate embryogenesis and may open new ways to study the regulation of EMT in vitro.

Molecular mechanisms in uterine epithelium during trophoblast binding: the role of small GTPase RhoA in human uterine Ishikawa cells

Background

Embryo implantation requires that uterine epithelium develops competence to bind trophoblast to its apical (free) poles. This essential element of uterine receptivity seems to depend on a destabilisation of the apico-basal polarity of endometrial epithelium. Accordingly, a reorganisation of the actin cytoskeleton regulated by the small GTPase RhoA plays an important role in human uterine epithelial RL95-2 cells for binding of human trophoblastoid JAR cells. We now obtained new insight into trophoblast binding using human uterine epithelial Ishikawa cells.

Methods

Polarity of Ishikawa cells was investigated by electron microscopy, apical adhesiveness was tested by adhesion assay. Analyses of subcellular distribution of filamentous actin (F-actin) and RhoA in apical and basal cell poles were performed by confocal laser scanning microscopy (CLSM) with and without binding of JAR spheroids as well as with and without inhibition of small Rho GTPases by Clostridium difficile toxin A (toxin A). In the latter case, subcellular distribution of RhoA was additionally investigated by Western blotting.

Results

Ishikawa cells express apical adhesiveness for JAR spheroids and moderate apico-basal polarity. Without contact to JAR spheroids, significantly higher signalling intensities of F-actin and RhoA were found at the basal as compared to the apical poles in Ishikawa cells. RhoA was equally distributed between the membrane fraction and the cytosol fraction. Levels of F-actin and RhoA signals became equalised in the apical and basal regions upon contact to JAR spheroids. After inhibition of Rho GTPases, Ishikawa cells remained adhesive for JAR spheroids, the gradient of fluorescence signals of F-actin and RhoA was maintained while the amount of RhoA was reduced in the cytosolic fraction with a comparable increase in the membrane fraction.

Conclusion

Ishikawa cells respond to JAR contact as well as to treatment with toxin A with rearrangement of F-actin and small GTPase RhoA but seem to be able to modify signalling pathways in a way not elucidated so far in endometrial cells. This ability may be linked to the degree of polar organisation observed in Ishikawa cells indicating an essential role of cell phenotype modification in apical adhesiveness of uterine epithelium for trophoblast in vivo.

Human Uterine Epithelial RL95-2 Cells Reorganize Their Cytoplasmic Architecture with Respect to Rho Protein and F-Actin in Response to Trophoblast Binding

Embryo implantation is initiated by interaction of trophoblast with uterine epithelium via the apical cell poles of both partners. Using spheroids of human trophoblastoid JAR cells and monolayers of human uterine epithelial RL95-2 cells to simulate this initial interaction, we previously demonstrated that formation of stable cell-to-cell bonds depends on actin cytoskeleton (F-actin) and small GTPases of the Rho family, most likely RhoA. In this study, we determined the apical as well as the basal distribution of these proteins by fluorescence confocal microscopy before and after binding of JAR spheroids. We focussed on changes in cytoplasmic organization with respect to apicobasal polarity of RL95-2 cells. Before binding of spheroids, significantly higher fluorescence signals of RhoA [37 +/- 6 grey scale values (gsv)] and of F-actin (41 +/- 3 gsv) were found in the basal region of RL95-2 cells as compared to the apical pole (RhoA: 24 +/- 3 gsv, F-actin: 28 +/- 2 gsv). After binding of JAR spheroids, this apicobasal asymmetry was inverted (RhoA: 55 +/- 10 gsv apical vs. 25 +/- 3 gsv basal; F-actin: 108 +/- 17 gsv apical vs. 57 +/- 7 gsv basal). Inactivation of Rho GTPases in RL95-2 cells by Clostridium difficile toxin A leads to a loss of their apical adhesion competence, as previously published. Here, we observed a uniform distribution of RhoA and F-actin between apical and basal region rather than an asymmetric one in toxin A-treated cells. These data suggest that activation of Rho GTPases and coordinated rearrangement of F-actin within uterine epithelial cells in response to trophoblast binding are part of a generalized structural and functional reorganization of the cytoplasm. This involves not only the immediate contact zone (apical) but also the opposite (basal) cell pole and may be a critical element of uterine epithelial reactions during transition between trophoblast adhesion and transmigration.

Adhesiveness of human uterine epithelial RL95-2 cells to trophoblast: rho protein regulation

Embryo implantation involves adhesion of trophoblast cells to the epithelial lining of the endometrium. Using an in-vitro model to simulate this initial interaction, we previously reported that attachment of human trophoblast-like JAR spheroids to human uterine epithelial RL95-2 cells provokes a Ca(2+) influx in RL95-2 cells depending on apically localized integrin receptors. Here, we demonstrate that adhesiveness of RL95-2 cells for JAR spheroids, measured by a centrifugal force-based adhesion assay, is dependent on Rho GTPases, most likely RhoA. Cellular expression and distribution of RhoA were studied by fluorescence confocal microscopy, focusing on the localization of RhoA and F-actin within the adhesion sites between JAR and RL95-2 cells. Contact areas contained high amounts of RhoA and F-actin fibres near the plasma membrane. To determine whether Rho GTPases may influence JAR cell binding, we treated RL95-2 cells with Clostridium difficile toxin A, which specifically inactivates Rho GTPases. Toxin A treatment changed the subcellular distribution of endogenous RhoA in RL95-2 cells and altered RhoA and F-actin colocalization. Adhesion of JAR spheroids to RL95-2 cells treated with toxin A was largely suppressed. These data indicate that Rho GTPases, most likely RhoA, play an important role in uterine epithelial RL95-2 cells for trophoblast binding, and suggest that RhoA may be involved in local signalling cascades during early embryo implantation in vivo.