Real-time high-resolution compound imaging allows percutaneous initiation and surveillance in an orthotopic murine pancreatic cancer model

Innovative Experimental Ultrasound and US-Related Techniques Using the Murine Model in Pancreatic Ductal Adenocarcinoma: A Systematic Review

Pancreatic ductal adenocarcinoma (PDAC) is a cancer with one of the highest mortality rates in the world. Several studies have been conductedusing preclinical experiments in mice to find new therapeutic strategies. Experimental ultrasound, in expert hands, is a safe, multifaceted, and relatively not-expensive device that helps researchers in several ways. In this systematic review, we propose a summary of the applications of ultrasonography in a preclinical mouse model of PDAC. Eighty-eight studies met our inclusion criteria. The included studies could be divided into seven main topics: ultrasound in pancreatic cancer diagnosis and progression (n: 21); dynamic contrast-enhanced ultrasound (DCE-US) (n: 5); microbubble ultra-sound-mediated drug delivery; focused ultrasound (n: 23); sonodynamic therapy (SDT) (n: 7); harmonic motion elastography (HME) and shear wave elastography (SWE) (n: 6); ultrasound-guided procedures (n: 9). In six cases, the articles fit into two or more sections. In conclusion, ultrasound can be a really useful, eclectic, and ductile tool in different diagnostic areas, not only regarding diagnosis but also in therapy, pharmacological and interventional treatment, and follow-up. All these multiple possibilities of use certainly represent a good starting point for the effective and wide use of murine ultrasonography in the study and comprehensive evaluation of pancreatic cancer.

Use of Transabdominal Ultrasound for the detection of intra-peritoneal tumor engraftment and growth in mouse xenografts of epithelial ovarian cancer

OBJECTIVE

To evaluate intraperitoneal (IP) tumor engraftment, metastasis and growth in a pre-clinical murine epithelial ovarian cancer (EOC) model using both transabdominal ultrasound (TAUS) and bioluminescence in vivo imaging system (IVIS).

METHODS

Ten female C57Bl/6J mice at six weeks of age were included in this study. Five mice underwent IP injection of 5x106 ID8-luc cells (+ D- luciferin) and the remaining five mice underwent IP injection of ID8-VEGF cells. Monitoring of tumor growth and ascites was performed weekly starting at seven days post-injection until study endpoint. ID8-luc mice were monitored using both TAUS and IVIS, and ID8-VEGF mice underwent TAUS monitoring only. Individual tumor implant dimension and total tumor volume were calculated. Average luminescent intensity was calculated and reported per mouse abdomen. Tumor detection was confirmed by gross evaluation and histopathology. All data are presented as mean +/- standard deviation.

RESULTS

Overall, tumors were successfully detected in all ten mice using TAUS and IVIS, and tumor detection correlated with terminal endpoint histology/ H&E staining. For TAUS, the smallest confirmed tumor measurements were at seven days post-injection with mean long axis of 2.23mm and mean tumor volume of 4.17mm3. However, IVIS imaging was able to detect tumor growth at 14 days post-injection. Ascites formation was detected in mice at 21 days post-injection.

CONCLUSIONS

TAUS is highly discriminatory for monitoring EOC in pre-clinical murine model, allowing for detection of tumor dimension as small as 2 mm and as early as seven days post-injection compared to IVIS. In addition, TAUS provides relevant information for ascites development and detection of multiple small metastatic tumor implants. TAUS provides an accurate and reliable method to detect and monitor IP EOC growth in mouse xenografts.

Size-dependent Tumor Response to Photodynamic Therapy and Irinotecan Monotherapies Revealed by Longitudinal Ultrasound Monitoring in an Orthotopic Pancreatic Cancer Model

Longitudinal monitoring of tumor size in vivo can provide important biological information about disease progression and treatment efficacy that is not captured by other modes of quantification. Ultrasound enables high-throughput evaluation of orthotopic mouse models via fast acquisition of three-dimensional tumor images and calculation of volume with a reasonable degree of accuracy. Herein, we compare orthotopic pancreatic tumor volume measurements determined by ultrasound with volume measured by calipers and tumor weight, and found strong correlations between the three modalities over a large range of tumor sizes, suggesting ultrasound can accurately quantify tumor volumes in this model. Furthermore, we demonstrate the unique ability of longitudinal treatment monitoring to reveal a tumor size-dependent response to Benzoporphyrin Derivative photodynamic therapy (BPD-PDT) and irinotecan. Small tumors (5-35 mm³ ) were found to respond well to a single round of PDT, while large tumors (35-65 mm³ ) showed no response to the same treatment. These results highlight the role that tumor size can play in preclinical interpretation of treatment response and more generally suggest that careful evaluation of subtle biological features such as this must be carefully considered in order to grant a more comprehensive understanding of disease biology in vivo.

Dabigatran potentiates gemcitabine-induced growth inhibition of pancreatic cancer in mice

Pancreatic cancer is one of the most lethal solid malignancies with little treatment options. We have recently shown that expression of protease activated receptor (PAR)-1 in the tumor microenvironment drives progression and induces chemoresistance of pancreatic cancer. As thrombin is the prototypical PAR-1 agonist, here we addressed the effect of the direct thrombin inhibitor dabigatran on pancreatic cancer growth and drug resistance in an orthotropic pancreatic cancer model. We show that dabigatran treatment did not affect primary tumor growth whereas it significantly increased tumor dissemination throughout the peritoneal cavity. Increased dissemination was accompanied by intratumoral bleeding and increased numbers of aberrant and/or collapsed blood vessels in the primary tumors. In combination with gemcitabine, dabigatran treatment limited primary tumor growth, did not induce bleeding complications and prevented tumor cell dissemination. Dabigatran was however not as efficient as genetic ablation of PAR-1 in our previous study suggesting that thrombin is not the main PAR-1 agonist in the setting of pancreatic cancer. Overall, we show that dabigatran potentiates gemcitabine-induced growth inhibition of pancreatic cancer but does not affect primary tumor growth when used as a monotherapy.

High-Resolution Ultrasound Allows Percutaneous Initiation and Surveillance of Prostate Cancer in an Orthotopic Murine Model

Introduction: Prostate cancer xenografts should prefer orthotopic growth to subcutaneous tumors as the former more closely mimics the natural tumor environment. However, these models are technically demanding and require an invasive laparotomy. To overcome these problems, we evaluated a minimally invasive approach by performing percutaneous prostate puncture under the control of high-resolution ultrasound imaging. Materials and Methods: Orthotopic tumor cell inoculation was performed in two groups of mice, i.e. in 10 nude mice via ultrasound-guided inoculation and in another 10 nude mice via an open surgical approach. Tumor growth was monitored after 4, 5 and 6 weeks by means of a high-resolution ultrasound system. Results: High-resolution ultrasound allowed exact tumor growth monitoring. After ultrasound-guided inoculation, 8 of 10 animals showed tumor engraftment. The surgical procedure was successful in 9 of 10 animals. Tumor volume was slightly but not significantly greater after surgical tumor induction. Our work demonstrates that tumor cell inoculation via percutaneous puncture of the prostate is feasible, less time-consuming and minimally invasive compared to an open surgical approach. This reduces the animal burden. Conclusion: Although the tumor size and the precision of inoculation is lower compared to the open surgical technique, this novel procedure enables real-time prostate punctures, suggesting the feasibility of other procedures including biopsy and local drug applications.

Animal models of pancreatic cancer for drug research

BACKGROUND

The operative and conservative results of therapy in pancreatic ductal adenocarcinoma remain appallingly poor. This underlines the demand for further research for effective anticancer drugs. The various animal models remain the essential method for the determination of efficacy of substances during preclinical phase.

OBJECTIVE

Unfortunately, most of these tested substances showed a good efficacy in pancreatic carcinoma in the animal model but were not confirmed during the clinical phase.

METHODS

The available literature in PubMed, Medline, Ovid and secondary literature was searched regarding the available animal models for drug testing against pancreatic cancer. The models were analyzed regarding their pros and cons in anticancer drug testing.

CONCLUSION

The different modifications of the orthotopic model (especially in mice) seem at present to be the best model for anticancer testing in pancreatic carcinoma. The value of genetically engineered animal model (GEM) and syngeneic models is on debate. A good selection of the model concerning the questions supposed to be clarified may improve the comparability of the results of animal experiments compared to clinical trials.

Over-expression of miR-106b promotes cell migration and metastasis in hepatocellular carcinoma by activating epithelial-mesenchymal transition process

Hepatocellular carcinoma (HCC) is one the the most fatal cancers worldwide. The poor prognosis of HCC is mainly due to the developement of distance metastasis. To investigate the mechanism of metastasis in HCC, an orthotopic HCC metastasis animal model was established. Two sets of primary liver tumor cell lines and corresponding lung metastasis cell lines were generated. In vitro functional analysis demonstrated that the metastatic cell line had higher invasion and migration ability when compared with the primary liver tumor cell line. These cell lines were subjected to microRNA (miRNAs) microarray analysis to identify differentially expressed miRNAs which were associated with the developement of metastasis in vivo. Fifteen human miRNAs, including miR-106b, were differentially expressed in 2 metastatic cell lines compared with the primary tumor cell lines. The clinical significance of miR-106b in 99 HCC clinical samples was studied. The results demonstrated that miR-106b was over-expressed in HCC tumor tissue compared with adjacent non-tumor tissue (p = 0.0005), and overexpression of miR-106b was signficantly correlated with higher tumor grade (p = 0.018). Further functional studies demonstrated that miR-106b could promote cell migration and stress fiber formation by over-expressing RhoGTPases, RhoA and RhoC. In vivo functional studies also showed that over-expression of miR-106b promoted HCC metastasis. These effects were related to the activation of the epithelial-mesenchymal transition (EMT) process. Our results suggested that miR-106b expression contributed to HCC metastasis by activating the EMT process promoting cell migration in vitro and metastasis in vivo.

cis-Hydroxyproline-mediated pancreatic carcinoma growth inhibition in mice

PURPOSE

This study addressed the question of whether the collagen metabolism modulator cis-4-Hydroxy-L-proline (CHP) is applicable for potential use as a therapeutic inhibitor of pancreatic carcinoma cell growth.

METHODS

Cell proliferation, as well as quantification of apoptosis of murine Panc02 cells, was assessed after CHP treatment. Supplementary, the effect of CHP on tumor growth was examined in the subcutaneous Panc02 model in vivo. Mice received daily intraperitoneal injections of CHP (300, 400, and 500 mg/kg bw). In addition to the assessment of systemic parameters (blood count, enzyme activities), histology (HE) and immunohistochemistry (Ki-67) were performed from resected tumor specimens.

RESULTS

Like reduction of metabolic activity, CHP also induced inhibition of cell growth in a dose-dependent manner, with however only slight increases in apoptosis. In vivo treatment of Panc02 tumors with CHP resulted in pronounced delay of tumor growth and decreases in tumor cell proliferation. Moreover, these effects were accompanied by a massive systemic leukocytosis as well increased leukocyte infiltration into the tumors subsequent to CHP therapy.

CONCLUSIONS

CHP inhibits the proliferation of Panc02 tumor cells in a dose-dependent manner both in vitro and in vivo. Our presented data show that modulation of the collagen metabolism is an interesting strategy for treatment of pancreatic carcinoma.

In vivo bioluminescent imaging of irradiated orthotopic pancreatic cancer xenografts in nonobese diabetic-severe combined immunodeficient mice: a novel method for targeting and assaying efficacy of ionizing radiation

Adenocarcinoma of the pancreas is a lethal malignancy, and better models to study tumor behavior in vivo are needed for the development ofmore effective therapeutics. Ionizing radiation is a treatment modality that is commonly used in the clinical setting, in particular, for locally confined disease; however, good model systems to study the effect of ionizing radiation in orthotopic tumors have not been established. In an attempt to create clinically relevant models for studying treatments directed against pancreatic cancer, we have defined a methodology to measure the effect of varying doses of radiation in established human pancreatic cancer orthotopic xenografts using two different pancreatic cancer cell lines (Panc-1 and BXPC3) infected with a lentiviral vector expressing CMV promoter-driven luciferase to allow bioluminescence imaging of live animals in real time. Quantifiable photon emission from luciferase signaling in vivo correlated well with actual tumor growth. Bioluminescence imaging of the established pancreatic xenografts was used to direct delivery of radiation to the orthotopic tumors and minimize off-target adverse effects. Growth delay was observed with schedules in the range of 7.5 Gy in five fractions to 10 Gy in four fractions, whereas doses 3 Gy or higher produced toxic adverse effects. In conclusion, we describe a model in which the effects of ionizing radiation, alone or in combination with other therapeutics, in orthotopic xenografts, can be studied.

Increase of in vivo antitumoral activity by CD40L (CD154) gene transfer into pancreatic tumor cell-dendritic cell hybrids

OBJECTIVES

Fusion of dendritic cells (DC) with tumor cells is an approach in immunotherapy combining antigenicity and capacity of antigen presentation to activate T cells for the induction of tumor-specific cytotoxic immunity. Although there have been reports of clinical benefit, response rates have been limited and further improvements are warranted.

METHODS

We used murine DC and a novel protocol for an effective fusion of those cells with the murine pancreatic cell line Panc02.

RESULTS

We observed 2 events: only moderate in vitro and in vivo cytotoxicity of tumor cell/DC hybrids and a down-regulation of costimulatory molecules on fused cells. Therefore, we transfected tumor cell/DC hybrids with an adenovirus expressing CD154 to improve DC activation and generating antitumor immune response without the need of CD4 T cells. High CD154 expression could be obtained by transfection of DC and Panc02 cells prior fusion. Furthermore, vaccination with CD154-transfected tumor cell/DC hybrid led to a significantly increased induction of cytotoxic T cells in vitro and to an improved antitumoral effect in an orthotopic in vivo mouse model.

CONCLUSIONS

CD154-transfected tumor cell/DC hybrids are a promising approach to increase the efficiency of antitumoral response.