Selective portal vein injection for the design of syngeneic models of liver malignancy

Orthotopic and metastatic tumour models in preclinical cancer research

Mouse models of disease play a pivotal role at all stages of cancer drug development. Cell-line derived subcutaneous tumour models are predominant in early drug discovery, but there is growing recognition of the importance of the more complex orthotopic and metastatic tumour models for understanding both target biology in the correct tissue context, and the impact of the tumour microenvironment and the immune system in responses to treatment. The aim of this review is to highlight the value that orthotopic and metastatic models bring to the study of tumour biology and drug development while pointing out those models that are most likely to be encountered in the literature. Important developments in orthotopic models, such as the increasing use of early passage patient material (PDXs, organoids) and humanised mouse models are discussed, as these approaches have the potential to increase the predictive value of preclinical studies, and ultimately improve the success rate of anticancer drugs in clinical trials.

Attenuation of peripheral serotonin inhibits tumor growth and enhances immune checkpoint blockade therapy in murine tumor models

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Modeling pancreatic cancer in mice for experimental therapeutics

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive malignancy that is characterized by early metastasis, low resectability, high recurrence, and therapy resistance. The experimental mouse models have played a central role in understanding the pathobiology of PDAC and in the preclinical evaluation of various therapeutic modalities. Different mouse models with targetable pathological hallmarks have been developed and employed to address the unique challenges associated with PDAC progression, metastasis, and stromal heterogeneity. Over the years, mouse models have evolved from simple cell line-based heterotopic and orthotopic xenografts in immunocompromised mice to more complex and realistic genetically engineered mouse models (GEMMs) involving multi-gene manipulations. The GEMMs, mostly driven by KRAS mutation(s), have been widely accepted for therapeutic optimization due to their high penetrance and ability to recapitulate the histological, molecular, and pathological hallmarks of human PDAC, including comparable precursor lesions, extensive metastasis, desmoplasia, perineural invasion, and immunosuppressive tumor microenvironment. Advanced GEMMs modified to express fluorescent proteins have allowed cell lineage tracing to provide novel insights and a new understanding about the origin and contribution of various cell types in PDAC pathobiology. The syngeneic mouse models, GEMMs, and target-specific transgenic mice have been extensively used to evaluate immunotherapies and study therapy-induced immune modulation in PDAC yielding meaningful results to guide various clinical trials. The emerging mouse models for parabiosis, hepatic metastasis, cachexia, and image-guided implantation, are increasingly appreciated for their high translational significance. In this article, we describe the contribution of various experimental mouse models to the current understanding of PDAC pathobiology and their utility in evaluating and optimizing therapeutic modalities for this lethal malignancy.

Role of SSH1 in colorectal cancer prognosis and tumor progression

BACKGROUND AND AIM

Slingshot 1 protein (SSH1) plays a critical role in cytoskeleton dynamic regulation. Increasing evidence suggest that SSH1 expression is upregulated in several cancers and relates to tumor progression and drug resistance. Here, we evaluated the role of SSH1 in colorectal cancer (CRC) development and its prognostic value in patients with CRC.

METHODS

SSH1 expression was examined by quantitative real-time polymerase chain reaction, western blot analysis, or immunohistochemistry. The association between SSH1 expression and clinical characteristics and prognosis was evaluated. Stable SSH1 knockdown cells were used for in vitro assays and xenograft models. Correlation between SSH1 expression and epithelial-mesenchymal transition (EMT) was analyzed by western blot and online data analysis.

RESULTS

SSH1 expression was upregulated in cancer tissue compared with paired non-cancerous tissue in patients with CRC. SSH1 expression level in CRC tissue was associated with tumor stage, lymph node metastasis, and correlated with poor prognosis as indicated by univariate and multivariate analyses. In vitro, loss of SSH1 impaired colony formation, migration, and invasion of CRC cells. In vivo data suggest that SSH1 could promote the progression and metastasis of CRC. Interestingly, E-cadherin, ZEB1, and Snail, which are markers of EMT, had a significant expression correlation with SSH1.

CONCLUSIONS

SSH1 expression is associated with CRC progression and predicts poor prognosis. SSH1 may promote CRC tumor progression by regulating EMT.

Hydroxyl safflower yellow A regulates the tumor immune microenvironment to produce an anticancer effect in a mouse model of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a serious threat to human health. Chemotherapy drugs such as cisplatin are widely used in cancer treatment, but can cause severe side effects. Hydroxyl safflower yellow A (HSYA) is a water-soluble chalcone glycoside substance extracted from safflowers (Carthamus tinctorius L.) that has been reported to inhibit tumor growth with few side effects. The tumor immune microenvironment is crucial for the proliferation and invasiveness of tumor cells, and it is mediated by forkhead box P3-positive (FOXP3+) regulatory T cells (Tregs) and retinoic acid receptor-related orphan receptor-γ (RORγ)-expressing Th17 cells. FOXP3+ Tregs inhibit immunoreaction and FOXP3 is a key indicator of Tregs. RORγ isoform 2, also known as RORγt, is an important transcription factor in Th17 cells that may promote cancer progression. In the present study, the antitumor effect of HSYA on HCC was investigated, as well as its impact on the tumor immune microenvironment. Following the establishment of a mouse model for HCC, hematoxylin and eosin staining were performed to observe histological changes in liver tumors, and the spleen and thymus were weighed to calculate the spleen and thymus indexes. The proportion of FOXP3+ Tregs in the spleen was determined by flow cytometry, and expression levels of Foxp3 and Rorγt were examined by reverse transcription-quantitative polymerase chain reaction and western blot analysis. The results of the present study showed that cisplatin inhibited tumor growth, caused weight loss and reduced the immunoreactivity of the mice. HSYA inhibited tumor growth without causing significant weight loss. The proportion of FOXP3-expressing Tregs in the spleen and the expression of Foxp3 and Rorγt mRNA decreased following treatment with certain doses of HSYA. In conclusion, HSYA inhibited tumor growth without detrimental effects on the weight of the mice, indicating that HSYA may be suitable as a novel therapy for HCC patients.

Development of an orthotopic syngeneic murine model of colorectal cancer for use in translational research

Improving outcomes in colorectal cancer requires more accurate in vivo modelling of the disease in humans, allowing more reliable pre-clinical assessment of potential therapies. Novel imaging techniques are necessary to improve the longitudinal assessment of disease burden in these models, reducing the number of animals required for translational studies. This report describes the development of an immune-competent syngeneic orthotopic murine model of colorectal cancer, utilising caecal implantation of CT26 cells stably transfected with the luciferase gene into immune-competent BALB/c mice, allowing serial bioluminescent imaging of cancer progression. Luminescence in the stably transfected CT26 cell line, after pre-conditioning in the flank of a BALB/c mouse, accurately reflected cell viability and resulted in primary caecal tumours in five of eight (63%) mice in the initial pilot study following caecal injection. Luminescent signal continued to increase throughout the study period with one mouse (20%) developing a liver metastasis. Histopathological assessment confirmed tumours to be consistent with a poorly differentiated adenocarcinoma. We have now performed this technique in 68 immune-competent BALB/c mice. There have been no complications from the procedure or peri-operative deaths, with primary tumours developing in 44 (65%) mice and liver metastases in nine (20%) of these. This technique provides an accurate model of colorectal cancer with tumours developing in the correct microenvironment and metastasising to the liver with a similar frequency to that seen in patients presenting with colorectal cancer, with serial bioluminescent reducing the murine numbers required in studies by removing the need for cull for assessment of disease burden.

Radiomics of liver MRI predict metastases in mice

Background

The purpose of this study was to investigate whether any texture features show a correlation with intrahepatic tumor growth before the metastasis is visible to the human eye.

Methods

Eight male C57BL6 mice (age 8–10 weeks) were injected intraportally with syngeneic MC-38 colon cancer cells and two mice were injected with phosphate-buffered saline (sham controls). Small animal magnetic resonance imaging (MRI) at 4.7 T was performed at baseline and days 4, 8, 12, 16, and 20 after injection applying a T2-weighted spin-echo sequence. Texture analysis was performed on the images yielding 32 texture features derived from histogram, gray-level co-occurrence matrix, gray-level run-length matrix, and gray-level size-zone matrix. The features were examined with a linear regression model/Pearson correlation test and hierarchical cluster analysis. From each cluster, the feature with the lowest variance was selected.

Results

Tumors were visible on MRI after 20 days. Eighteen features from histogram and the gray-level-matrices exhibited statistically significant correlations before day 20 in the experiment group, but not in the control animals. Cluster analysis revealed three distinct clusters of independent features. The features with the lowest variance were Energy, Short Run Emphasis, and Gray Level Non-Uniformity.

Conclusions

Texture features may quantitatively detect liver metastases before they become visually detectable by the radiologist.

The Allosteric Hemoglobin Effector ITPP Inhibits Metastatic Colon Cancer in Mice

OBJECTIVE

To test the effects of enhanced intracellular oxygen contents on the metastatic potential of colon cancer.

BACKGROUND

Colorectal cancer is the commonest gastrointestinal carcinoma. Distant metastases occur in half of patients and are responsible for most cancer-related deaths. Tumor hypoxia is central to the pathogenesis of metastases. Myo-Inositoltrispyrophosphate (ITPP), a nontoxic, antihypoxic compound, has recently shown significant benefits in experimental cancer, particularly when combined with standard chemotherapy. Whether ITPP protects from distant metastases in primary colon cancer is unknown.

METHODS

ITPP alone or combined with FOLFOX was tested in a mouse model with cecal implantation of green fluorescent protein-labeled syngeneic colorectal cancer cells. Tumor development was monitored through longitudinal magnetic resonance imaging-based morphometric analysis and survival. Established serum markers of tumor spread were measured serially and circulating tumor cells were detected via fluorescence measurements.

RESULTS

ITPP significantly reduced the occurrence of metastases as well as other indicators of tumor aggressiveness. Less circulating tumor cells along with reduction in malignant serum markers (osteopontin, Cxcl12) were noted. The ITPP benefits also affected the primary cancer site. Importantly, animals treated with ITPP had a significant survival benefit compared with respective controls, while a combination of FOLFOX with ITPP conferred the maximum benefits, including dramatic improvements in survival (mean 86 vs 188 d).

CONCLUSIONS

Restoring oxygen in metastatic colon cancer through ITPP inhibits tumor spread and markedly improves animal survival; an effect that is enhanced through the application of subsequent chemotherapy. These promising novel findings call for a clinical trial on ITPP in patients with colorectal cancer, which is under way.

A Portal Vein Injection Model to Study Liver Metastasis of Breast Cancer

Breast cancer is the leading cause of cancer-related mortality in women worldwide. Liver metastasis is involved in upwards of 30% of cases with breast cancer metastasis, and results in poor outcomes with median survival rates of only 4.8 - 15 months. Current rodent models of breast cancer metastasis, including primary tumor cell xenograft and spontaneous tumor models, rarely metastasize to the liver. Intracardiac and intrasplenic injection models do result in liver metastases, however these models can be confounded by concomitant secondary-site metastasis, or by compromised immunity due to removal of the spleen to avoid tumor growth at the injection site. To address the need for improved liver metastasis models, a murine portal vein injection method that delivers tumor cells firstly and directly to the liver was developed. This model delivers tumor cells to the liver without complications of concurrent metastases in other organs or removal of the spleen. The optimized portal vein protocol employs small injection volumes of 5 - 10 μl, ≥ 32 gauge needles, and hemostatic gauze at the injection site to control for blood loss. The portal vein injection approach in Balb/c female mice using three syngeneic mammary tumor lines of varying metastatic potential was tested; high-metastatic 4T1 cells, moderate-metastatic D2A1 cells, and low-metastatic D2.OR cells. Concentrations of ≤ 10,000 cells/injection results in a latency of ~ 20 - 40 days for development of liver metastases with the higher metastatic 4T1 and D2A1 lines, and > 55 days for the less aggressive D2.OR line. This model represents an important tool to study breast cancer metastasis to the liver, and may be applicable to other cancers that frequently metastasize to the liver including colorectal and pancreatic adenocarcinomas.