Endoscopy-guided orthotopic implantation of colorectal cancer cells results in metastatic colorectal cancer in mice

Spheroids and organoids derived from colorectal cancer as tools for in vitro drug screening

Colorectal cancer (CRC) is a heterogeneous disease. Conventional two-dimensional (2D) culture employing cell lines was developed to study the molecular properties of CRC in vitro. Although these cell lines which are isolated from the tumor niche in which cancer develop, the translation to human model such as studying drug response is often hindered by the inability of cell lines to recapture original tumor features and the lack of heterogeneous clinical tumors represented by this 2D model, differed from in vivo condition. These limitations which may be overcome by utilizing three-dimensional (3D) culture consisting of spheroids and organoids. Over the past decade, great advancements have been made in optimizing culture method to establish spheroids and organoids of solid tumors including of CRC for multiple purposes including drug screening and establishing personalized medicine. These structures have been proven to be versatile and robust models to study CRC progression and deciphering its heterogeneity. This review will describe on advances in 3D culture technology and the application as well as the challenges of CRC-derived spheroids and organoids as a mode to screen for anticancer drugs.

High Engraftment and Metastatic Rates in Orthotopic Xenograft Models of Gastric Cancer via Direct Implantation of Tumor Cell Suspensions

Although the implantation of intact tumor fragments is a common practice to generate orthotopic xenografts to study tumor invasion and metastasis, the direct implantation of tumor cell suspensions is necessary when prior manipulations of tumor cells are required. However, the establishment of orthotopic xenografts using tumor cell suspensions is not mature, and a comparative study directly comparing their engraftment and metastatic capabilities is lacking. It is unclear whether tumor fragments are superior to cell suspensions for successful engraftment and metastasis. In this study, we employed three GC cell lines with varying metastatic capacities to stably express firefly luciferase for monitoring tumor progression in real time. We successfully minimized the risk of cell leakage during the orthotopic injection of tumor cell suspensions without Corning Matrigel by systematically optimizing the surgical procedure, injection volume, and needle size options. Comparable high engraftment and metastatic rates between these two methods were demonstrated using MKN-45 cells with a strong metastatic ability. Importantly, our approach can adjust the rate of tumor progression flexibly and cuts the experimental timeline from 10-12 weeks (for tumor fragments) to 4-5 weeks. Collectively, we provided a highly reproducible procedure with a shortened experimental timeline and low cost for establishing orthotopic GC xenografts via the direct implantation of tumor cell suspensions.

An immunocompetent rectal cancer model to study radiation therapy

We describe a mouse model of rectal cancer (RC) involving rapid tumor organoid engraftment via orthotopic transplantation in an immunocompetent setting. This approach uses simple mechanical disruption to allow engraftment, avoiding the use of dextran sulfate sodium. The resulting RC tumors invaded from the mucosal surface and metastasized to distant organs. Histologically, the tumors closely resemble human RC and mirror remodeling of the tumor microenvironment in response to radiation. This murine RC model thus recapitulates key aspects of human RC pathogenesis and presents an accessible approach for more physiologically accurate, preclinical efficacy studies.

Recent advances in the development of transplanted colorectal cancer mouse models

Despite progress in prevention and treatment, colorectal cancer (CRC) remains the third most common malignancy worldwide and the second most common cause of cancer death in 2020. To evaluate various characteristics of human CRC, a variety of mouse models have been established. Transplant mouse models have distinct advantages in studying the clinical behavior and therapeutic progress of CRC. Host, xenograft, and transplantation routes are the basis of transplant mouse models. As the effects of the tumor microenvironment and the systemic environment on cancer cells are gradually revealed, 3 key elements of transplanted CRC mouse models have been revolutionized. This has led to the development of humanized mice, patient-derived xenografts, and orthotopic transplants that reflect the human systemic environment, patient's tumor of origin, and tumor growth microenvironments in immunodeficient mice, respectively. These milestone events have allowed for great progress in tumor biology and the treatment of CRC. This article reviews the evolution of these events and points out their strengths and weaknesses as innovative and useful preclinical tools to study CRC progression and metastasis and to exploit novel treatment schedules by establishing a testing platform. This review article depicts the optimal transplanted CRC mouse models and emphasizes the significance of surgical models in the study of CRC behavior and treatment response.

Targeting FHL2-E-cadherin axis by miR-340-5p attenuates colon cancer cell migration and invasion

Convincing data has suggested that four and a half LIM domain 2 protein (FHL2) serves a key function in cancer cell metastasis and that microRNA (miR)-340-5p can regulate cancer cell migration. The current study hypothesized that targeting FHL2 expression by miR-340-5p in colon cancer may attenuate colon cancer cell migration and invasion. FHL2 expression was therefore assessed in colon cancer microarray datasets using Qlucore omics explorer as well as in HT-29 and AZ-97 colon cancer cell lines via reverse transcription-quantitative PCR (RT-qPCR). Colon cancer cell migration and invasion were evaluated in the presence of miR-340-5p mimic, mimic control or mimic with a target site blocker. Confocal microscopy and RT-qPCR were subsequently performed to assess FHL2, E-cadherin (E-cad) protein and mRNA expression in colon cancer cells. Microarray dataset analysis revealed that FHL2 expression was lower in primary colon cancer cells compared with normal colonic mucosa. It was revealed that the expression of miR-340-5p and FHL2 were inversely related in serum-grown and low-serum conditions in HT-29 and AZ-97 cells. Short-time serum exposure to low-serum grown cells induced FHL2 expression. Transfection of HT-29 cells with miR-340-5p mimic not only decreased serum-induced expression of FHL2 but also decreased cancer cell migration and invasion. Bioinformatics analysis revealed that FHL2 mRNA had one putative binding site for miR-340-5p at the 3-untranslated region. Blocking of the target site using a specific blocker reverted miR-340-5p mimic-induced inhibition of FHL2 expression and cancer cell migration and invasion. Confocal microscopy confirmed that the reduction of FHL2 expression by miR-340-5p mimic also reversed serum-induced E-cad disruption and that the target site blocker abrogated the effect of miR-340-5p. The current results suggested that miR-340-5p could be used to antagonize colon cancer cell metastasis by targeting the FHL2-E-cad axis.

Establishment of an Endoscopy-Guided Minimally Invasive Orthotopic Mouse Model of Colorectal Cancer

Simple Summary

Open orthotopic mouse models of colorectal cancer have disadvantages such as the requirement for advanced surgical skills or the trauma caused by laparotomy. To overcome these limitations, this study aimed to evaluate the establishment of an endoscopy-guided minimally invasive model without laparotomy. Different concentrations of the murine CRC cell lines CT26 and MC38 were endoscopically injected into the colorectal wall of BALB/C and C57BL/6J mice, respectively. Consistent tumor growth with the presence of tumor-infiltrating lymphocytes, lympho-vascular invasion, and early spontaneous lymph node, peritoneal, and hepatic metastases were observed. Analysis of the learning curve demonstrated that this model is easy to learn and quick to establish. It enables intra-individual follow-up endoscopies, and features tumors to study mechanisms of metastasis and the interaction with the immune system. The application of specific cell lines and concentrations enables a controlled local tumor growth and metastatic formation within short observation periods.

Abstract

Open orthotopic mouse models of colorectal cancer have disadvantages such as the requirement for advanced surgical skills or the trauma caused by laparotomy. To overcome these drawbacks, this study aimed to evaluate the establishment of a minimally invasive model using murine colonoscopy. CT26 and MC38 CRC cells of different concentrations were injected into BALB/C and C57BL/6J mice, respectively. Follow-up endoscopies were performed to assign an endoscopic score to tumor growth. Gross autopsy, histologic and immuno-histochemical evaluation, and immune scoring were performed. To describe the learning curve of the procedures, a performance score was given. Local tumor growth with colorectal wall infiltration, luminal ulceration, the presence of tumor-infiltrating lymphocytes, lympho-vascular invasion, and early spontaneous lymph node, peritoneal, and hepatic metastases were observed. The tumors showed cytoplasmic immuno-staining for CK20. Compared to the MC38/C57BL/6J model, tumorigenicity and immunogenicity of the CT26/BALB/C model were higher. Tumor volume correlated with the endoscopic score. This endoscopy-guided orthotopic mouse model is easy to learn and quick to establish. It features early metastasis and enables the study of interactions with the immune system. When specific cell concentrations and cell lines are applied, controlled local tumor growth and metastasis can be achieved within short observation periods.

MicroRNA-340-5p inhibits colon cancer cell migration via targeting of RhoA

Colon cancer is the third most common cancer and a significant cause of cancer-related deaths worldwide. Metastasis is the most insidious aspect of cancer progression. Convincing data suggest that microRNAs (miRs) play a key function in colon cancer biology. We examined the role of miR-340-5p in regulating RhoA expression as well as cell migration and invasion in colon cancer cells. Levels of miR-340-5p and RhoA mRNA varied inversely in serum-free and serum-grown HT-29 and AZ-97 colon cancer cells. It was found transfection with miR-340-5p not only decreased expression of RhoA mRNA and protein levels in HT-29 cells but also reduced colon cancer cell migration and invasion. Bioinformatics analysis predicted one putative binding sites at the 3'-UTR of RhoA mRNA. Targeting this binding site with a specific blocker reversed mimic miR-340-5p-induced inhibition of RhoA activation and colon cancer cell migration and invasion. These novel results suggest that miR-340-5p is an important regulator of colon cancer cell motility via targeting of RhoA and further experiments are warranted to evaluate the role of miR-340-5p in colon cancer metastasis.

A novel patient-derived organoids-based xenografts model for preclinical drug response testing in patients with colorectal liver metastases

Backgrounds

Cancer-related mortality in patients with colorectal cancer (CRC) is predominantly caused by development of colorectal liver metastases (CLMs). How to screen the sensitive chemotherapy and targeted therapy is the key element to improve the prognosis of CLMs patients. The study aims to develop patient-derived organoids-based xenografted liver metastases (PDOX-LM) model of CRC, to recapitulate the clinical drug response.

Methods

We transplanted human CRC primary tumor derived organoids in murine spleen to obtain xenografted liver metastases in murine liver. Immunohistochemistry (IHC) staining, whole-exome and RNA sequencing, and drug response testing were utilized to identify the homogeneity in biological and genetic characteristics, and drug response between the PDOX-LM models and donor liver metastases.

Results

We successfully established PDOX-LM models from patients with CLMs. IHC staining showed that positive expression of CEA, Ki67, VEGF, FGFR2 in donor liver metastases were also well preserved in matched xenografted liver metastases. Whole-exon sequencing and transcriptome analysis showed that both xenografted and donor liver metastases were highly concordant in somatic variants (≥ 0.90 frequency of concordance) and co-expression of driver genes (Pearson’s correlation coefficient reach up to 0.99, P = 0.001). Furthermore, drug response testing showed that the PDOX-LM models can closely recapitulated the clinical response to mFOLFOX6 regiments.

Conclusions

This PDOX-LM model provides a more convenient and informative platform for preclinical testing of individual tumors by retaining the histologic and genetic features of donor liver metastases. This technology holds great promise to predict treatment sensitivity for patients with CLMs undergoing chemotherapy.

Mouse models of colorectal cancer: Past, present and future perspectives

Colorectal cancer (CRC) is the third most common diagnosed malignancy among both sexes in the United States as well as in the European Union. While the incidence and mortality rates in western, high developed countries are declining, reflecting the success of screening programs and improved treatment regimen, a rise of the overall global CRC burden can be observed due to lifestyle changes paralleling an increasing human development index. Despite a growing insight into the biology of CRC and many therapeutic improvements in the recent decades, preclinical in vivo models are still indispensable for the development of new treatment approaches. Since the development of carcinogen-induced rodent models for CRC more than 80 years ago, a plethora of animal models has been established to study colon cancer biology. Despite tenuous invasiveness and metastatic behavior, these models are useful for chemoprevention studies and to evaluate colitis-related carcinogenesis. Genetically engineered mouse models (GEMM) mirror the pathogenesis of sporadic as well as inherited CRC depending on the specific molecular pathways activated or inhibited. Although the vast majority of CRC GEMM lack invasiveness, metastasis and tumor heterogeneity, they still have proven useful for examination of the tumor microenvironment as well as systemic immune responses; thus, supporting development of new therapeutic avenues. Induction of metastatic disease by orthotopic injection of CRC cell lines is possible, but the so generated models lack genetic diversity and the number of suited cell lines is very limited. Patient-derived xenografts, in contrast, maintain the pathological and molecular characteristics of the individual patient’s CRC after subcutaneous implantation into immunodeficient mice and are therefore most reliable for preclinical drug development – even in comparison to GEMM or cell line-based analyses. However, subcutaneous patient-derived xenograft models are less suitable for studying most aspects of the tumor microenvironment and anti-tumoral immune responses. The authors review the distinct mouse models of CRC with an emphasis on their clinical relevance and shed light on the latest developments in the field of preclinical CRC models.

Diffuse reflectance spectroscopy to monitor murine colorectal tumor progression and therapeutic response

SIGNIFICANCE

Many studies in colorectal cancer (CRC) use murine ectopic tumor models to determine response to treatment. However, these models do not replicate the tumor microenvironment of CRC. Physiological information of treatment response derived via diffuse reflectance spectroscopy (DRS) from murine primary CRC tumors provide a better understanding for the development of new drugs and dosing strategies in CRC.

AIM

Tumor response to chemotherapy in a primary CRC model was quantified via DRS to extract total hemoglobin content (tHb), oxygen saturation (StO2), oxyhemoglobin, and deoxyhemoglobin in tissue.

APPROACH

A multimodal DRS and imaging probe (0.78 mm outside diameter) was designed and validated to acquire diffuse spectra longitudinally-via endoscopic guidance-in developing colon tumors under 5-fluoruracil (5-FU) maximum-tolerated (MTD) and metronomic regimens. A filtering algorithm was developed to compensate for positional uncertainty in DRS measurements Results: A maximum increase in StO2 was observed in both MTD and metronomic chemotherapy-treated murine primary CRC tumors at week 4 of neoadjuvant chemotherapy, with 21  ±  6  %   and 17  ±  6  %   fold changes, respectively. No significant changes were observed in tHb.

CONCLUSION

Our study demonstrates the feasibility of DRS to quantify response to treatment in primary CRC models.

Near-Infrared Fluorescent Activated Polymeric Probe for Imaging Intraluminal Colorectal Cancer Tumors

Detection and removal of preneoplastic tumors is crucial for successful colorectal cancer (CRC) therapy. Here we describe the design of a Cathepsin B (CB)-activated polymeric probe, P-(GGFLGK-IR783), for imaging CRC tumors established by intrarectal or subcutaneous (s.c.) implantation of human colon cancer cells (SW-480 and HT-29) in mice. Multiple copies of the near-infrared fluorescent (NIRF) dye IR783 were attached to a single HPMA copolymer backbone via a CB-cleavable linker (GFLG), and the influence of the dye loading on the fluorescence quenching and activation by CB was assessed in vitro, ex vivo, and in vivo. The optimal dose and dosing regimen of P-(GGFLGK-IR783) for colonic tumor detection was determined. Increasing the IR783 loading in the copolymer from 2.5 to 20 mol % resulted in quenching of the fluorescence signal that was activated in vitro by the action of CB from different origins. Following intravenous administration, P-(GGFLGK-IR783)_7.5% preferentially accumulated in intrarectal and s.c. implanted tumors, allowing tumor visualization after 4 h and even 48 h postadministration. Activation of P-(GGFLGK-IR783)_7.5% by CB was clearly detected in s.c. implanted tumors, revealing about a 4-fold increase in the fluorescence signal in tumors vs healthy colon tissue. The probe containing the CB-cleavable linker produced higher fluorescence signal intensity in tumors, relative to the noncleavable probe. These results indicate that P-(GGFLGK-IR783)_7.5% may aid in detecting CRC tumors and can help to guide selective removal of polyps during colonoscopic procedures.

Molecular imaging of MMP activity discriminates unstable from stable plaque phenotypes in shear-stress induced murine atherosclerosis

Purpose

As atherosclerotic plaque ruptures are the primary cause of ischaemic events, their preventive identification by imaging remains a clinical challenge. Matrix metalloproteinases (MMP) are involved in plaque progression and destabilisation and are therefore promising targets to characterize rupture-prone unstable plaques. This study aims at evaluating MMP imaging to discriminate unstable from stable plaque phenotypes.

Methods

ApoE deficient mice (ApoE^-/-) on a high cholesterol diet underwent implantation of a tapered cuff around the right common carotid artery (CCA) inducing a highly inflamed atherosclerotic plaque upstream (US) and a more stable plaque phenotype downstream (DS) of the cuff. 8 weeks after surgery, the MMP inhibitor-based photoprobe Cy5.5-AF443 was administered i.v. 3h prior to in situ and ex vivo fluorescence reflectance imaging of the CCAs. Thereafter, CCAs were analysed regarding plaque size, presence of macrophages, and MMP-2 and MMP-9 concentrations by immunohistochemistry and ELISA.

Results

We found a significantly higher uptake of Cy5.5-AF443 in US as compared to DS plaques in situ (1.29 vs. 1.06 plaque-to-background ratio; p<0.001), which was confirmed by ex vivo measurements. Immunohistochemistry revealed a higher presence of macrophages, MMP-2 and MMP-9 in US compared to DS plaques. Accordingly, MMP-2 concentrations were significantly higher in US plaques (47.2±7.6 vs. 29.6±4.6 ng/mg; p<0.05).

Conclusions

In the ApoE^-/- cuff model MMP-2 and MMP-9 activities are significantly higher in upstream low shear stress-induced unstable atherosclerotic plaques as compared to downstream more stable plaque phenotypes. MMP inhibitor-based fluorescence molecular imaging allows visualization of these differences in shear stress-induced atherosclerosis.

Assessment of MMP-2/-9 expression by fluorescence endoscopy for evaluation of anastomotic healing in a murine model of anastomotic leakage

BACKGROUND

Disturbance of intestinal wound closure leads to insufficient anastomotic healing and is associated with considerable morbidity following colorectal resections. Matrix metalloproteinases (MMPs) play a crucial role in regulation of wound closure. Here fluorescence endoscopy was evaluated for assessment of MMP-2/-9 expression during failed intestinal anastomotic healing.

METHODS

Distal colonic anastomoses were performed as a model for disturbed healing in 36 Balb/c mice. Healing was evaluated endoscopically, macroscopically, and histologically after 1, 3 and 5 days. For detection of MMP-2/-9 expression fluorescence endoscopy (FE) was used following i.v.-administration of a Cy5.5-labeled MMP-2/-9 specific tracer. FE was complemented by quantification of the fluorescence signal using the MS-FX PRO Optical Imaging System. An overall leakage score was calculated and correlated with the results of FE.

RESULTS

With increasing incidence of anastomotic leakage from POD1 (17%) to POD5 (83%) the uptake of the MMP tracer gradually increased (signal-to-noise ratio (SNR), POD1: 17.91 ± 1.251 vs. POD3: 30.56 ± 3.03 vs. POD5: 44.8 ± 4.473, P<0.0001). Mice with defective anastomotic healing showed significantly higher uptake compared to non-defective (SNR: 37.37± 3.63 vs. 26.16± 3.635, P = 0.0369). White light endoscopy and FE allowed evaluation of anastomotic healing and visualization of mucosal MMPs in vivo. Using FE based detection of MMPs in the anastomosis, an overall positive predictive value of 71.4% and negative predictive value of 66.6% was calculated for detection of anastomotic leakage.

CONCLUSION

During disturbed anastomotic healing increased expression of MMP-2/-9 was observed in the anastomotic tissue. Fluorescence endoscopy for detection of MMP-2/-9 during the healing process might be a promising tool for early identification of anastomotic leakage.

Colonoscopy-based colorectal cancer modeling in mice with CRISPR-Cas9 genome editing and organoid transplantation

Most genetically engineered mouse models (GEMMs) of colorectal cancer are limited by tumor formation in the small intestine, a high tumor burden that limits metastasis, and the need to generate and cross mutant mice. Cell line or organoid transplantation models generally produce tumors in ectopic locations-such as the subcutaneous space, kidney capsule, or cecal wall-that do not reflect the native stromal environment of the colon mucosa. Here, we describe detailed protocols to rapidly and efficiently induce site-directed tumors in the distal colon of mice that are based on colonoscopy-guided mucosal injection. These techniques can be adapted to deliver viral vectors carrying Cre recombinase, CRISPR-Cas9 components, CRISPR-engineered mouse tumor organoids, or human cancer organoids to mice to model the adenoma-carcinoma-metastasis sequence of tumor progression. The colonoscopy injection procedure takes ∼15 min, including preparation. In our experience, anyone with reasonable hand-eye coordination can become proficient with mouse colonoscopy and mucosal injection with a few hours of practice. These approaches are ideal for a wide range of applications, including assessment of gene function in tumorigenesis, examination of tumor-stroma interactions, studies of cancer metastasis, and translational research with patient-derived cancers.

Targeting Mucosal Endothelin-A-Receptor Expression by Fluorescence Endoscopy is Feasible to Detect and Characterize Colitis-Associated Cancer in Mice

BACKGROUND

To facilitate onsite decision-making during endoscopy, both accurate detection and in vivo characterization of preneoplasia are prerequisites. However, no endoscopy technique is available that meets both demands satisfactorily. We evaluated endothelin-receptor A (ETAR)-guided fluorescence endoscopy (FE) in vivo and fluorescence reflectance imaging (FRI) ex vivo for detection and characterization of early dysplastic colitis-associated colonic lesions.

METHODS

Colorectal cancerogenesis was investigated in the inflammatory driven AOM-DSS model and spontaneous adenoma development in ApcMin mice. A Cy5.5-labeled nonpeptidic ETAR-specific imaging probe was injected intravenously to assess tumor development in vivo by white light endoscopy (WLE) and FE. Ex vivo tumors were evaluated by FRI, histological examination, and western blot analysis. In addition, tissue samples from patients with colitis-associated malignant and nonmalignant mucosal alterations were analyzed. Specificity experiments were performed using an unspecific Cy3.5-glycine tracer.

RESULTS

Overall, 62 adenomas were observed. FE was able to detect and quantify ETAR expression targeting the ETAR-specific photoprobe. A significantly higher fluorescent contrast was detected in colonic adenomas compared to adjacent nonmalignant mucosa by FE (64.3 ± 7.9 vs. 56.6. ± 7.0; P < 0.001). These results were confirmed by FRI examination, immunochemistry, and western blot analysis. Additionally, ETAR expression in samples from human patients with colitis-associated cancer was highly elevated compared to nonmalignant alterations. Specificity experiments indicated a high binding-specificity of the applied ETAR photoprobe (1.4 ± 0.3 vs. 2.5 ± 0.7; P < 0.001).

CONCLUSIONS

We introduced ETAR guided FE in mice for successful in vivo detection and characterization of colorectal neoplasia on a molecular level.

Tumor location impacts immune response in mouse models of colon cancer

Existing preclinical models of human colorectal cancer (CRC) that rely on syngeneic subcutaneous grafts are problematic, because of increasing evidence that the immune microenvironment in subcutaneous tissue is significantly different from the gastrointestinal tract. Similarly, existing orthotopic models that use a laparotomy for establishing grafts are also problematic, because the surgical procedure results in extensive inflammation, thereby creating a nonphysiologic tumor microenvironment. To facilitate the bench-to-bedside translation of CRC immunotherapy strategies, we developed a novel orthotopic model in mice that uses endoscopy-guided microinjection of syngeneic cancer cells. When we compared immune system infiltration, we found that tumors in the subcutaneous model had fewer T cells, B cells, and natural killer (NK) cells, but more immunosuppressive myeloid cells; in contrast, tumors in our orthotopic model had a higher number of tumor-infiltrating T cells, B cells, and NK cells, with fewer immunosuppressive myeloid cells. The number of immune-stimulating cytokines, such as interleukin (IL)-2, IL-6, interferon (IFN)-gamma, and granzyme B, was also higher in tumors in our model, as compared with the subcutaneous model. Those differences resulted in heightened sensitivity to immune checkpoint blockade therapy in our endoscopy-guided orthotopic CRC model. Our study indicates that tumor location affects immune response in CRC mouse models; choosing the appropriate preclinical model is important when testing immunotherapy in CRC.