Development of a metastatic murine colon cancer model

Advancing Pain Understanding and Drug Discovery: Insights from Preclinical Models and Recent Research Findings

Despite major advancements in our understanding of its fundamental causes, pain-both acute and chronic-remains a serious health concern. Various preclinical investigations utilizing diverse animal, cellular, and alternative models are required and frequently demanded by regulatory approval bodies to bridge the gap between the lab and the clinic. Investigating naturally occurring painful disorders can speed up medication development at the preclinical and clinical levels by illuminating molecular pathways. A wide range of animal models related to pain have been developed to elucidate pathophysiological mechanisms and aid in identifying novel targets for treatment. Pain sometimes drugs fail clinically, causing high translational costs due to poor selection and the use of preclinical tools and reporting. To improve the study of pain in a clinical context, researchers have been creating innovative models over the past few decades that better represent pathological pain conditions. In this paper, we provide a summary of traditional animal models, including rodents, cellular models, human volunteers, and alternative models, as well as the specific characteristics of pain diseases they model. However, a more rigorous approach to preclinical research and cutting-edge analgesic technologies may be necessary to successfully create novel analgesics. The research highlights from this review emphasize new opportunities to develop research that includes animals and non-animals using proven methods pertinent to comprehending and treating human suffering. This review highlights the value of using a variety of modern pain models in animals before human trials. These models can help us understand the different mechanisms behind various pain types. This will ultimately lead to the development of more effective pain medications.

An orthotopic metastatic xenograft model of colorectal cancer

Colorectal cancer (CRC) presents a substantial global health challenge, prompting the necessity for the development and validation of preclinical models to enhance our comprehension and therapeutic interventions. Among the myriad of murine models available for CRC evaluation, orthotopic implantation via intercaecal microinjection stands out as a preferred method for replicating the intricate tumor microenvironment while ensuring uniformity and standardized applicability. In this study, we delineate a methodology addressing the required steps for tumor cell line selection and reporter transduction, animal model preparation, orthotopic tumor implantation, in vivo monitoring of tumor growth and metastasis formation. We comprehensively describe the generation of a xenograft murine model based on the intercaecal implantation of human GFP+/luciferase+ SW620 CRC cells, facilitating the evaluation of responses to pre-clinical human-based therapeutic approaches. The implementation of these standardized protocols promises to augment the reliability and reproducibility of preclinical studies, ultimately advancing our comprehension of CRC pathogenesis and guiding the development of innovative therapeutic strategies.

Integrin-linked kinase expression in myeloid cells promotes colon tumorigenesis

Colorectal cancer (CRC) is one of the most common forms of cancer worldwide and treatment options for advanced CRC, which has a low 5-year survival rate, remain limited. Integrin-linked kinase (ILK), a multifunctional, scaffolding, pseudo-kinase regulating many integrin-mediated cellular processes, is highly expressed in many cancers. However, the role of ILK in cancer progression is yet to be fully understood. We have previously uncovered a pro-inflammatory role for myeloid-specific ILK in dextran sodium sulfate (DSS)-induced colitis. To establish a correlation between chronic intestinal inflammation and colorectal cancer (CRC), we investigated the role of myeloid-ILK in mouse models of CRC. When myeloid-ILK deficient mice along with the WT control mice were subjected to colitis-associated and APCmin/+-driven CRC, tumour burden was reduced by myeloid-ILK deficiency in both models. The tumour-promoting phenotype of macrophages, M2 polarization, in vitro was impaired by the ILK deficiency and the number of M2-specific marker CD206-expressing tumour-associated macrophages (TAMs) in vivo were significantly diminished in myeloid-ILK deficient mice. Myeloid-ILK deficient mice showed enhanced tumour infiltration of CD8+ T cells and reduced tumour infiltration of FOXP3+ T cells in colitis-associated and APCmin/+-driven CRC, respectively, with an overall elevated CD8+/FOXP3+ ratio suggesting an anti-tumour immune phenotypes. In patient CRC tissue microarrays we observed elevated ILK+ myeloid (ILK+ CD11b+) cells in tumour sections compared to adjacent normal tissues, suggesting a conserved role for myeloid-ILK in CRC development in both human and animal models. This study identifies myeloid-specific ILK expression as novel driver of CRC, which could be targeted as a potential therapeutic option for advanced disease.

Conjugated Bile Acids Accelerate Progression of Pancreatic Cancer Metastasis via S1PR2 Signaling in Cholestasis

BACKGROUND

Pancreatic cancer (PC) has an extremely high mortality rate, where obstructive jaundice due to cholestasis is a classic symptom. Conjugated bile acids (CBAs) such as taurocholic acid (TCA) have been reported to activate both the ERK1/2 and AKT signaling pathways via S1P receptor 2 (S1PR2) and promote growth of cholangiocarcinoma. Thus, we hypothesize that CBAs, which accumulate in cholestasis, accelerate PC progression via S1PR2.

METHODS

Murine Panc02-luc and human AsPC-1, MIA PaCa2, and BxPC-3 cells were treated with TCA, S1PR2 agonist CYM5520, S1PR2 antagonist JTE-013, sphingosine-1-phosphate (S1P), and functional S1P receptor antagonist (except S1PR2) FTY720. Bile duct ligation (BDL) was performed on liver implantation or intraperitoneal injection of Panc02-luc cells.

RESULTS

Panc02-luc and AsPC-1 cells predominantly expressed S1PR2, and their growth and migration were stimulated by TCA or CYM5520 in dose-dependent manner, which was blocked by JTE-013. This finding was not seen in PC cell lines expressing other S1P receptors than S1PR2. Panc02-luc growth stimulation by S1P was not blocked by FTY720. BDL significantly increased PC liver metastasis compared with sham. PC peritoneal carcinomatosis was significantly worsened by BDL, confirmed by number of nodules, tumor weight, bioluminescence, Ki-67 stain, ascites, and worse survival compared with sham. CYM5520 significantly worsened PC carcinomatosis, whereas treatment with anti-S1P antibody or FTY720 also worsened progression.

CONCLUSIONS

CBAs accelerated growth of S1PR2 predominant PC both in vitro and in vivo. This finding implicates S1PR2 as a potential therapeutic target in metastatic S1PR2 predominant pancreatic cancer.

Trends in Subcutaneous Tumour Height and Impact on Measurement Accuracy

Tumour volume is typically calculated using only length and width measurements, using width as a proxy for height in a 1:1 ratio. When tracking tumour growth over time, important morphological information and measurement accuracy is lost by ignoring height, which we show is a unique variable. Lengths, widths, and heights of 9522 subcutaneous tumours in mice were measured using 3D and thermal imaging. The average height:width ratio was found to be 1:3 proving that using width as a proxy for height overestimates tumour volume. Comparing volumes calculated with and without tumour height to the true volumes of excised tumours indeed showed that using the volume formula including height produced volumes 36X more accurate (based off of percentage difference). Monitoring the height:width relationship (prominence) across tumour growth curves indicated that prominence varied, and that height could change independent of width. Twelve cell lines were investigated individually; the scale of tumour prominence was cell line-dependent with relatively less prominent tumours (MC38, BL2, LL/2) and more prominent tumours (RENCA, HCT116) detected. Prominence trends across the growth cycle were also dependent on cell line; prominence was correlated with tumour growth in some cell lines (4T1, CT26, LNCaP), but not others (MC38, TC-1, LL/2). When pooled, invasive cell lines produced tumours that were significantly less prominent at volumes >1200 mm³ compared to non-invasive cell lines (P < .001). Modelling was used to show the impact of the increased accuracy gained by including height in volume calculations on several efficacy study outcomes. Variations in measurement accuracy contribute to experimental variation and irreproducibility of data, therefore we strongly advise researchers to measure height to improve accuracy in tumour studies.

The Antitumor and Toxicity Effects of Ruthenium(II) Complexes on Heterotopic Murine Colon Carcinoma Model

The aim of the present study was to examine the antitumor and toxicity effects of ruthenium(II) complexes, [Ru(Cltpy)(en)Cl][Cl] (Ru-1) and [Ru(Cl-tpy)(dach)Cl][Cl] (Ru-2) on heterotopic murine colon carcinoma model.

For tumor induction, 1×106 CT26 cells suspended in 100 μl of DMEM were injected subcutaneously into flank of male BALB/c mice. Treatment groups were as follows: Ru-1, Ru-2, oxaliplatin and control (saline). The intraperitoneal administration of the tested complexes began on 6th day after CT26 cells inoculation. Each complex was administered at dose of 5 mg/kg, twice weekly, four doses in total. To assess toxicity, serum values of urea, creatinine, AST and ALT were determined and histopathological analysis of organs and tumor were performed. In order to assess the effects of Ru(II) complexes on markers of oxidative stress and antioxidant defense system, we determined the TBARS, GSH, SOD and CAT in the homogenate of tumor, heart, liver, lungs and kidney tissues.

The findings indicate that Ru-1 and Ru-2 exerts equal or better antitumor activity in comparison with oxaliplatin, but with pronounced toxic effects such as reduced survival rate, cardiotoxicity, nephrotoxicity and hepatotoxicity. The increased index of lipid peroxidation in the tissues of the kidneys and heart, but decreased in tumor tissue, after Ru(II) complexes administration, indicates the importance of the induction of oxidative stress as a possible mechanism of nephrotoxicity and cardiotoxicity, but not the mechanism by which they realize antitumor activity.

Additional studies are needed to elucidate the mechanism of antitumor activity and toxicity of the Ru(II) complexes.

Research Status of Mouse Models for Non-Small-Cell Lung Cancer (NSCLC) and Antitumor Therapy of Traditional Chinese Medicine (TCM) in Mouse Models

Non-small-cell lung cancer (NSCLC) is known as one of the most lethal cancers, causing more than 1 million deaths annually worldwide. Therefore, the development of novel therapeutic drugs for NSCLC has become an urgent need. Herein, various mouse models provide great convenience not only for researchers but also for the development of antitumor drug. Meanwhile, TCM, as a valuable and largely untapped resource pool for modern medicine, provides research resources for the treatment of various diseases. Until now, cell-derived xenograft (CDX) model, patient-derived xenograft (PDX) model, syngeneic model, orthotopic model, humanized mouse model (HIS), and genetically engineered mouse models (GEMMs) have been reported in TCM evaluation. This review shows the role and current status of kinds of mouse models in antitumor research and summarizes the application progress of TCM including extracts, formulas, and isolated single molecules for NSCLC therapy in various mouse models; more importantly, it provides a theoretical exploration of what kind of mouse models is ideal for TCM efficacy evaluation in future. However, there are still huge challenges and limitations in the development of mouse models specifically for the TCM research, and none of the available models are perfectly matching the characteristics of TCM, which suppress the tumor growth through various mechanisms, especially by regulating immune function. Nevertheless, with fully functional immune system existing in syngeneic model and humanized mouse model (HIS), it is still suggested that these two models are more suitable for development of TCM especially for TCM extracts or formulas. Moreover, continued efforts are needed to generate more reliable mouse models to test TCM formulas in future research.

Selective thyroid hormone receptor beta agonist, GC-1, is capable to reduce growth of colorectal tumor in syngeneic mouse models

OBJECTIVE

The effect of thyroid hormone (TH) on cancers was proposed more than 100 years ago; however, conclusions are conflicting. THs are precisely regulated at tissue and cellular levels. It seems that this regulation is altered in cancers. Thyroid hormone receptor beta (TRβ) has anti-proliferative and tumor-suppressive effects in many cancer cells. Therefore, we decided to investigate thyroid hormone receptor beta (THRB) expression and activation by the selective agonist, GC-1, on tumor growth in a syngeneic mouse model of colorectal cancer (CRC) and colon cell lines.

METHODS

In vitro cell viability assay using MTT analysis, cell cycle analysis by PI staining, and FACS analysis were performed. In vivo tumor growth measurements were carried out by caliper and [¹⁸F] Fluoro-2-deoxy-2-D-glucose (FDG) - PET imaging. Gene expressions were determined using quantitative-PCR.

RESULTS

Some concentrations of GC-1 had a marked negative effect on the cell viability of colorectal cell lines. Cell cycle analysis showed that the anti-proliferative effect of GC-1 may not result from cell cycle arrest or apoptosis. Tumor growth analysis in mice harboring colorectal tumor showed that GC-1 treatment for 8 d profoundly inhibited tumor growth and ¹⁸FDG uptake. THRB expression was decreased in mice tumor; however, it was upregulated following GC-1 administration.

CONCLUSIONS

Our results showed that specific activation of TRβ by GC-1 had negative effect on tumor growth and restored its gene expression in tumors of CRC mice model.

Therapeutic efficacy and gastrointestinal biodistribution of polycationic nanoparticles for oral camptothecin delivery in early and late-stage colorectal tumor-bearing animal model

Colorectal cancer (CRC) is the third most commonly diagnosed cancer in the world and is the second leading cause of cancer related deaths. New cases are increasingly diagnosed every day, but current therapeutic options are still insufficient for an effective treatment. In CRC treatment, there is a significant need for alternative treatment approaches that can both prevent relapse and provide strong antimetastatic effects as the intestines and colon are prone to metastasis to neighboring organs and tissues as well as the liver and the lung. In this study, optimized polycationic cyclodextrin (CD) nanoparticles for oral Camptothecin (CPT) delivery were comprehensively examined for in vivo performance in early and late stage tumor bearing mouse model in terms of antitumoral and antimetastatic efficacy of CPT bound to polycationic CD nanoparticles in comparison to free CPT. In addition, the gastrointestinal localization of a single administration of fluorescent dye loaded polycationic CD nanoparticles in the gastrointestinal tract at the end of 24 hours after oral administration was also imaged and evaluated by in vivo imaging system against fluorescent dye intensity. Results showed that survival percentage was significantly improved in CRC-bearing mice compared to oral CPT solution, with significantly reduced colorectal tumor masses and number of liver metastatic foci (p<0.05). It was also possible to differentiate between the effectiveness of nanoparticles in early or late stages of CRC. In vivo imaging studies have also confirmed that polycationic CD nanoparticles are able to deliver the therapeutic load up to the colon and tend to accumulate especially in tumor foci, indicating an effective local treatment strategy. In addition number of liver metastases were significantly decreased with the CPT-loaded polycationic CD nanoparticle formulation in both early and late stage tumor models. These findings indicated that CPT-loaded polycationic CD nanoparticles could be an efficient oral nanocarrier formulation for anticancer molecules that have limited application because of oral bioavailability and stability problems.

Tumor-Secreted Extracellular Vesicles Regulate T-Cell Costimulation and Can Be Manipulated To Induce Tumor-Specific T-Cell Responses

BACKGROUND & AIMS

Colorectal cancer is a major cause of cancer-related deaths worldwide. Immune checkpoint blockade therapies are effective in 30%-60% of the microsatellite instable-high subtype. Unfortunately, most patients with colorectal cancer (>85%) have microsatellite stable tumors that do not respond. In this study, we aimed to decipher the underlying tumor-intrinsic mechanisms critical for improving immunotherapy in colorectal cancer.

METHODS

We used human and mouse tumor samples, cell lines, human colorectal cancer organoids, and various syngeneic orthotopic mouse models of late-stage colorectal cancer to define the effects of tumor cell-secreted extracellular vesicles (EVs) on antitumor immune response.

RESULTS

Our analyses of human colorectal cancer immune profiles and tumor-immune cell interactions showed that tumor-secreted EVs containing microRNA miR-424 suppressed the CD28-CD80/86 costimulatory pathway in tumor-infiltrating T cells and dendritic cells, leading to immune checkpoint blockade resistance. Modified tumor-secreted EVs with miR-424 knocked down enhanced T-cell-mediated antitumor immune response in colorectal cancer tumor models and increased the immune checkpoint blockade response. Intravenous injections of modified tumor-secreted EVs induced tumor antigen-specific immune responses and boosted the immune checkpoint blockade efficacy in colorectal cancer models that mimic aggressively progressing, late-stage disease.

CONCLUSIONS

Collectively, we show a critical role for tumor-secreted EVs in antitumor immune regulation and immunotherapy response, which could be developed as a novel treatment for immune checkpoint blockade-resistant colorectal cancer.

Establishing metastatic patient-derived xenograft model for colorectal cancer

BACKGROUND

Patient-derived xenograft model is a powerful and promising tool for drug discovery and cancer biology studies. The application of previous metastatic colorectal cancer models has been greatly limited by its low success rate and long time to develop metastasis. Therefore, in this study, we aim to describe an optimized protocol for faster establishment of colorectal cancer metastatic patient-derived xenograft mouse models.

METHODS

Smaller micro tissues (˂150 μm in diameter) mixed with Matrigel were engrafted subcutaneously into NSG mice to generate the passage 1 (P1) patient-derived xenograft. The micro tumours from P1 patient-derived xenograft were then excised and orthotopically xenografted into another batch of NSG mice to generate a metastatic colorectal cancer patient-derived xenograft, P2. Haematoxylin and eosin and immunohistochemistry staining were performed to compare the characters between patient-derived xenograft tumours and primary tumours.

RESULTS

About 16 out of 18 P1 xenograft models successfully grew a tumour for 50.8 ± 5.1 days (success rate 89.9%). Six out of eight P1 xenograft models originating from metastatic patients successfully grew tumours in the colon and metastasized to liver or lung in the NSG recipients for 60.9 ± 4.5 days (success rate 75%). Histological examination of both P1 and P2 xenografts closely resembled the histological architecture of the original patients' tumours. Immunohistochemical analysis revealed similar biomarker expression levels, including CDH17, Ki-67, active β-catenin, Ki-67 and α smooth muscle actin when compared with the original patients' tumours. The stromal components that support the growth of patient-derived xenograft tumours were of murine origin.

CONCLUSIONS

Metastatic patient-derived xenograft mouse model could be established with shorter time and higher success rate. Although the patient-derived xenograft tumours were supported by the stromal cells of murine origin, they retained the dominant characters of the original patient tumours.

Gut Fecal Microbiota Transplant in a Mouse Model of Orthotopic Rectal Cancer

The gut microbiota is reported to play an important role in carcinogenesis and the treatment of CRC. SW480 and SW620 colon cancer cells integrated with infrared fluorescent proteins were injected into the rectal submucosa of nude mice. In the subsequent 30 days, we observed tumor growth weekly using an in vivo imaging system. The bacterial solution was infused anally into the mice to perform bacterial transplant. Phosphate-buffered saline, Acinetobacter lwoffii, and Bifidobacterium longum solutions were infused individually. The 16S ribosomal DNA (rDNA) and polymerase chain reaction of murine feces were investigated to confirm the colonization of target bacteria. In the SW620 orthotopic xenograft rectal cancer model, 4 of 5 mice developed rectal cancer by 30 days after submucosal injection. In the SW480 orthotopic xenograft rectal cancer model, 2 of 6 mice developed rectal cancer by 30 days after submucosal injection. For the 16S rDNA analysis, the mice receiving the bacterial solution infusion demonstrated positive findings for A. lwoffii and B. longum. With the successful establishment of a mouse model of orthotopic rectal cancer and transplant of target bacteria, we can further explore the relationship between gut microbiota and CRC. The role of fecal microbiota transplant in the treatment and alleviation of adverse events of chemotherapy in CRC could be clarified in subsequent studies.

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.

Comparison of Different Colorectal Cancer With Liver Metastases Models Using Six Colorectal Cancer Cell Lines

At present, modeling methods of colorectal cancer with liver metastases have significant limitations. Here, we established orthotopic and ectopic hepatic metastases models using six colorectal cancer cell lines to choose an ideal animal model for studying colorectal cancer growth and liver metastases. Luciferin-expressing six colorectal cancer cell lines were used to induce animal models of colorectal cancer with liver metastases by intra-splenic injection or implantation of tumor tissue in the caecum. Tumors growth and metastatic events were observed by bioluminescence imaging. In orthotopic transplantation group, six cell lines all had taken rates of 100% for orthotopic tumors but showed variations in rates of growth. HCT-116 cell developed the 50% liver metastases. However, the ectopic transplantation group achieved higher liver metastatic rate, with the highest frequencies for HCT116 cell (90%) and SW620 cell (77.8%). Furthermore, the time to develop liver metastases and survival rates of bearing-tumor mice were shorter than orthotopic transplantation group. Additionally, six colorectal cancer cell lines resulted in more lymph node metastases in orthotopic transplantation group, whereas produced widespread peritoneal seeding in ectopic transplantation group. Bioluminescence imaging and pathological findings confirmed the growth and metastatic characteristics of tumors. Two animal models of colorectal cancer using six cell lines showed highly variations in rates of growth, survival rates of bearing-tumor mice and frequencies of metastases. The study provides useful information for the establishment of clinically relevant colorectal cancer with liver metastases animal models.

Orthotopic Implantation Achieves Better Engraftment and Faster Growth Than Subcutaneous Implantation in Breast Cancer Patient-Derived Xenografts

Patient-Derived Xenograft (PDX) is now accepted as a murine model that better mimics human cancer when compared to a conventional cancer cell-line inoculation model. Some claim the advantage of orthotopic site implantation of patient tumor (OS) over ectopic implantation into the subcutaneous space (SQ); however, there has been no study that describes a head-to-head comparison of oncological differences between these two models to date. We hypothesize that OS tumors re-transplant and grow better than SQ tumors and are therefore a better model to evaluate tumor aggressiveness. Breast cancer PDXs were generated using the tumors derived from 11 patients into NOD scid gamma (NSG) mice. We used six ER(+)HER2(-) tumors and five triple negative (TN) tumors for a total of 11 tumors. Five PDX lines grew for an overall engraftment rate of 45%. We present our OS implantation method in detail. The re-transplantation rate of TN tumors in each transplant site was significantly higher in OS when compared to SQ tumors (70.1% vs. 32.1%, p < 0.01). OS tumors grow significantly faster than SQ tumors. Similarly, OS tumors demonstrated significantly more mitotic figures and Ki-67 positive cells than SQ tumors. The tumor re-transplantation rate significantly increased by the second and third generations with the OS method. The time from implantation to development of a palpable tumor dramatically decreased after the first passage. PDX of ER(+) tumors demonstrated significantly lower engraftment rates and slower tumor growth than TN tumors, which remarkably improved by the first passage. Orthotopically implanted PDX tumors showed better re-transplantation rates, greater tumor size, and more significant growth compared to the subcutaneously implanted model.

Reversing tumor stemness via orally targeted nanoparticles achieves efficient colon cancer treatment

The acquisition of stemness in colorectal cancer (CRC) attributed to the recurrence and metastasis in CRC treatment. Therefore, targeting the stemness of CRC forms a basis for the development of novel therapeutic approaches. However, the pain and systemic side effect from long-term of venipuncture injection remain great challenges to neoplastic treatment. Here, we introduce an oral drug delivery system for sustained release of BMI-1 inhibitor (PTC209) that reverses the stemness of CRC to overcome these obstacles. In this system, nanoparticles modified with hyaluronic acid (HA) showed high-affinity to CD44/CD168 overexpressed-CRC cells, and efficiently targeted to tumor site in a metastatic orthotropic colon cancer mouse model by oral administration. Significantly, the observed tumor growth inhibition is accompanied by decreased expression of stemness markers in the tumor tissues. Furthermore, HA-NPs-PTC209 also significantly prevented metastasis to the gastrointestinal system, while failing to exhibit acute side effects. In summary, we have developed an orally active, easily synthesized nanomedicine that shows promise for the treatment of colon cancer.

Improved Efficacy and Reduced Toxicity Using a Custom-Designed Irinotecan-Delivering Silicasome for Orthotopic Colon Cancer

Irinotecan is a key chemotherapeutic agent for the treatment of colorectal (CRC) and pancreatic (PDAC) cancer. Because of a high incidence of bone marrow and gastrointestinal (GI) toxicity, Onivyde (a liposome) was introduced to provide encapsulated irinotecan (Ir) delivery in PDAC patients. While there is an ongoing clinical trial (NCT02551991) to investigate the use of Onivyde as a first-line option to replace irinotecan in FOLFIRINOX, the liposomal formulation is currently prescribed as a second-line treatment option (in combination with 5-fluorouracil and leucovorin) for patients with metastatic PDAC who failed gemcitabine therapy. However, the toxicity of Onivyde remains a concern that needs to be addressed for use in CRC as well. Our goal was to custom design a mesoporous silica nanoparticle (MSNP) carrier for encapsulated irinotecan delivery in a robust CRC model. This was achieved by developing an orthotopic tumor chunk model in immunocompetent mice. With a view to increase the production volume and to expand the disease applications, the carrier design was improved by using an ethanol exchange method for coating of a supported lipid bilayer (LB) that entraps a protonating agent. The encapsulated protonating agent was subsequently used for remote loading of irinotecan. The excellent irinotecan loading capacity and stability of the LB-coated MSNP carrier, also known as a "silicasome", previously showed improved efficacy and reduced toxicity when compared to an in-house liposomal carrier in a PDAC model. Intravenous injection of the silicasomes in a well-developed orthotopic colon cancer model in mice demonstrated improved pharmacokinetics and tumor drug content over free drug and Onivyde. Moreover, improved drug delivery was accompanied by substantially improved efficacy, increased survival, and reduced bone marrow and GI toxicity compared to the free drug and Onivyde. We also confirmed that the custom-designed irinotecan silicasomes outperform Onivyde in an orthotopic PDAC model. In summary, the Ir-silicasome appears to be promising as a treatment option for CRC in humans based on improved efficacy and the carrier's favorable safety profile.

Generating a Murine Orthotopic Metastatic Breast Cancer Model and Performing Murine Radical Mastectomy

In vivo mouse models to assess breast cancer progression are essential for cancer research, including preclinical drug developments. However, the majority of the practical and technical details are commonly omitted in published manuscripts which, therefore, makes it challenging to reproduce the models, particularly when it involves surgical techniques. Bioluminescence technology allows for the evaluation of small amounts of cancer cells even when a tumor is not palpable. Utilizing luciferase-expressing cancer cells, we establish a breast cancer orthotopic inoculation technique with a high tumorigenesis rate. Lung metastasis is assessed utilizing an ex vivo technique. We, then, establish a mastectomy model with a low local recurrence rate to assess the metastatic tumor burden. Herein, we describe, in detail, the surgical techniques of orthotopic implantation and mastectomy for breast cancer with a high tumorigenesis rate and low local recurrence rates, respectively, to improve breast cancer model efficiency.

Two sides to colon cancer: mice mimic human anatomical region disparity in colon cancer development and progression

Aim:

Strong evidence reveals important differences between cancers in the proximal vs. distal colon. Animal models of metastatic colon cancer are available but with varying degrees of reproducibility and several important limitations. We explored whether there were regional differences in the location of murine colon cancers and assessed the utility of murine models to explore the biological basis for such differences.

Methods:

We re-analyzed data from our previous studies to assess the regional distribution of murine colon cancer. In survival surgery experiments, we injected HT-29 human colon cancer cells into the wall of the cecum or distal colon of Nu(NCr)-Foxn1^nu or NOD.Cg-Prkdc^scidIl2rg^Tim1Wji/SzJ mice and compared the development of primary tumors and metastases.

Results:

Within 7–17 weeks after intramural cecal injection of HT-29 cells, eight mice failed to develop solid primary tumors or metastases. In contrast, within four weeks after cell injection into the distal colon, 13 mice developed metastases - 12 mice developed subcutaneous metastases; of these, four developed liver metastases and one developed both liver and lung metastases. One mouse developed liver metastases only. Histological examination confirmed these lesions were adenocarcinomas.

Conclusion:

Our findings reveal the preferential growth of murine colon neoplasia and invasive human orthotopic xenografts in the distal mouse colon. The new approach of injecting cells into the distal colon wall results in a pattern of colon cancer development that closely mimics the progression of metastatic colon cancer in humans. This novel model of colon neoplasia has great potential for exploring anatomical differences in colon cancer and testing novel therapeutics.

Murine Models of Intraperitoneal Perfusion for Disseminated Colorectal Cancer

BACKGROUND

Reproduction of the perfusion used in therapy (hyperthermic intraperitoneal chemotherapy) procedures preclinically represents a valuable asset for investigating new therapeutic agents that may improve patient outcomes. This article provides technical descriptions of our execution of closed and open "coliseum" abdominal perfusion techniques in a mouse model of peritoneal carcinomatosis of colorectal cancer.

MATERIALS AND METHODS

BALB/c mice presenting with disseminated colorectal cancer (CT26-luciferin cells) underwent 30-min perfusions mimicking either the closed perfusion or the coliseum perfusion technique. Disease burden was monitored by bioluminescence signaling using an in vivo imaging system. Perfusion circuits consisted of single inflow lines with either a single or dual outflow line.

RESULTS

Twelve mice presenting with disseminated disease underwent the closed perfusion technique. Surgical complications included perfusate leakage and organ constriction/suction into the outflow line(s). Nine mice underwent the coliseum perfusion technique with surgical debulking, using bipolar cauterization to remove tumors attached to the peritoneum. All mice survived the coliseum perfusion with limited intraoperative complications.

CONCLUSIONS

Fewer intraoperative complications were experienced with our coliseum perfusion technique than the closed perfusion. The methods described here can be used as a guideline for developing future perfusion murine models for investigating perfusion models useful for delivery of chemotherapy or other tumor-sensitization agents, including selective targeted agents, nanoparticles, and heat.

Lactobacillus casei Variety rhamnosus Probiotic Preventively Attenuates 5-Fluorouracil/Oxaliplatin-Induced Intestinal Injury in a Syngeneic Colorectal Cancer Model

Adjuvant 5-fluorouracil (5-FU)-based chemotherapy, including FOLFOX (5-FU, leucovorin, and oxaliplatin), is recommended for colorectal cancer. However, intestinal mucositis remains a common adverse effect for which no effective preventive strategies are available. To develop a convenient and novel way to alleviate mucositis, we investigated the effect of Lactobacillus casei variety rhamnosus (Lcr35) on FOLFOX-induced mucosal injury. BALB/c mice subcutaneously injected with syngeneic CT26 colorectal adenocarcinoma cells were orally administered Lcr35 daily before, during, and after 5-day injection of FOLFOX regimen, for 14 days. The following methods were used: diarrhea score for toxicity, ELISA for cytokine production, histopathology for intestinal injury, immunohistochemistry for apoptosis/proliferation and regulatory proteins, RT-PCR for cytokine mRNA expression, and DNA sequencing for fecal gut microbiota. FOLFOX administration to colorectal cancer-bearing mice significantly inhibited tumor growth and the accompanying marked diarrhea and intestinal injury histologically characterized by the shortening of villi and destruction of intestinal crypts. Preventive administration of Lcr35 dose-dependently reduced the severity of diarrhea and intestinal mucositis without affecting the anti-tumor effect of FOLFOX. The numbers of apoptotic, NF-κB-, and BAX-activated cells increased after FOLFOX, and these responses were mitigated by Lcr35. TNF-α and IL-6 upregulation by FOLFOX treatment was attenuated by Lcr35. The fecal gut microbiota composition of Firmicutes and Bacteroidetes disturbed by FOLFOX was significantly reversed by Lcr35 toward a preferential profile. In conclusion, the oral probiotic Lcr35 prevented FOLFOX-induced intestinal mucositis in colorectal cancer-bearing mice. The putative mechanism might involve modulation of gut microbiota and proinflammatory responses with suppression of intrinsic apoptosis in intestinal injury.

Thermosensitive Injectable Hydrogel for Simultaneous Intraperitoneal Delivery of Doxorubicin and Prevention of Peritoneal Adhesion

To improve intraperitoneal chemotherapy and to prevent postsurgical peritoneal adhesion, we aimed to develop a drug delivery strategy for controlled release of a chemotherapeutic drug from the intraperitoneally injected thermosensitive poly(N-isopropylacrylamide)-based hydrogel (HACPN), which is also endowed with peritoneal anti-adhesion properties. Anticancer drug doxorubicin (DOX) was loaded into the hydrogel (HACPN-DOX) to investigate the chemotherapeutic and adhesion barrier effects in vivo. A burst release followed by sustained release of DOX from HACPN-DOX was found due to gradual degradation of the hydrogel. Cell culture studies demonstrated the cytotoxicity of released DOX toward CT-26 mouse colon carcinoma cells in vitro. Using peritoneal carcinomatosis animal model in BALB/c mice with intraperitoneally injected CT-26 cells, animals treated with HACPN-DOX revealed the best antitumor efficacy judging from tumor weight and volume, survival rate, and bioluminescence signal intensity when compared with treatment with free DOX at the same drug dosage. HACPN (or HACPN-DOX) also significantly reduced the risk of postoperative peritoneal adhesion, which was generated by sidewall defect-cecum abrasion in tumor-bearing BALB/c mice, from gross and histology analyses. This study could create a paradigm to combine controlled drug release with barrier function in a single drug-loaded injectable hydrogel to enhance the intraperitoneal chemotherapeutic efficacy while simultaneously preventing postsurgical adhesion.

ABCC1-Exported Sphingosine-1-phosphate, Produced by Sphingosine Kinase 1, Shortens Survival of Mice and Patients with Breast Cancer

Sphingosine-1-phosphate (S1P), a bioactive sphingolipid mediator, has been implicated in regulation of many processes important for breast cancer progression. Previously, we observed that S1P is exported out of human breast cancer cells by ATP-binding cassette (ABC) transporter ABCC1, but not by ABCB1, both known multidrug resistance proteins that efflux chemotherapeutic agents. However, the pathologic consequences of these events to breast cancer progression and metastasis have not been elucidated. Here, it is demonstrated that high expression of ABCC1, but not ABCB1, is associated with poor prognosis in breast cancer patients. Overexpression of ABCC1, but not ABCB1, in human MCF7 and murine 4T1 breast cancer cells enhanced S1P secretion, proliferation, and migration of breast cancer cells. Implantation of breast cancer cells overexpressing ABCC1, but not ABCB1, into the mammary fat pad markedly enhanced tumor growth, angiogenesis, and lymphangiogenesis with a concomitant increase in lymph node and lung metastases as well as shorter survival of mice. Interestingly, S1P exported via ABCC1 from breast cancer cells upregulated transcription of sphingosine kinase 1 (SPHK1), thus promoting more S1P formation. Finally, patients with breast cancers that express both activated SPHK1 and ABCC1 have significantly shorter disease-free survival. These findings suggest that export of S1P via ABCC1 functions in a malicious feed-forward manner to amplify the S1P axis involved in breast cancer progression and metastasis, which has important implications for prognosis of breast cancer patients and for potential therapeutic targets.Implication: Multidrug resistant transporter ABCC1 and activation of SPHK1 in breast cancer worsen patient's survival by export of S1P to the tumor microenvironment to enhance key processes involved in cancer progression. Mol Cancer Res; 16(6); 1059-70. ©2018 AACR.

Murine breast cancer mastectomy model that predicts patient outcomes for drug development

BACKGROUND

Despite massive expenditures in preclinical studies, many breast cancer agents show efficacy in murine models but fail in human trials. In humans, metastatic disease determines survival, but preclinical murine models only evaluate drug efficacy against the primary tumor. We hypothesized that evaluating efficacy against metastatic breast cancer would more efficiently predict efficacy in a murine model than evaluating the primary tumor alone. This study (1) critically evaluated a murine tumor removal model with metastatic tumor burden quantification for breast cancer preclinical trials and (2) validated the model with an agent that previously passed preclinical trials but failed human trials.

MATERIALS AND METHODS

Tumorectomy and Halsted (radical) mastectomy procedures after inoculation of 4T1-luc2 cells were compared. The effect of AZD0530, an oral Src inhibitor that passed preclinical trials but failed human trials, was evaluated using an inoculation model with/without Halsted mastectomy.

RESULTS

Significant amounts of residual disease were confirmed by bioluminescence (P = 0.003) and 100% developed local recurrence after tumorectomy versus 14% (P = 0.005) after Halsted mastectomy. Bioluminescence value at 15 min after luciferin injection highly correlated with peak except for 24 h after injection. AZD0530 significantly suppressed primary tumor burden compared with no treatment (P = 0.002); but not in lung metastases. In a Halsted mastectomy model, AZD0530 had no efficacy against lung metastases or difference in survival.

CONCLUSIONS

We critically evaluated and established a murine mastectomy model to evaluate metastatic tumors. It provides a new model for preclinical drug development that mimics the human adjuvant setting.

Luciferase Expression Allows Bioluminescence Imaging But Imposes Limitations on the Orthotopic Mouse (4T1) Model of Breast Cancer

Implantation of reporter-labeled tumor cells in an immunocompetent host involves a risk of their immune elimination. We have studied this effect in a mouse model of breast cancer after the orthotopic implantation of mammary gland adenocarcinoma 4T1 cells genetically labelled with luciferase (Luc). Mice were implanted with 4T1 cells and two derivative Luc-expressing clones 4T1luc2 and 4T1luc2D6 exhibiting equal in vitro growth rates. In vivo, the daughter 4T1luc2 clone exhibited nearly the same, and 4T1luc2D6, a lower growth rate than the parental cells. The metastatic potential of 4T1 variants was assessed by magnetic resonance, bioluminescent imaging, micro-computed tomography, and densitometry which detected 100-μm metastases in multiple organs and bones at the early stage of their development. After 3-4 weeks, 4T1 generated 11.4 ± 2.1, 4T1luc2D6, 4.5 ± 0.6; and 4T1luc2, <1 metastases per mouse, locations restricted to lungs and regional lymph nodes. Mice bearing Luc-expressing tumors developed IFN-γ response to the dominant CTL epitope of Luc. Induced by intradermal DNA-immunization, such response protected mice from the establishment of 4T1luc2-tumors. Our data show that natural or induced cellular response against the reporter restricts growth and metastatic activity of the reporter-labelled tumor cells. Such cells represent a powerful instrument for improving immunization technique for cancer vaccine applications.

Doxorubicin effect is enhanced by sphingosine-1-phosphate signaling antagonist in breast cancer

BACKGROUND

Doxorubicin is one of the most commonly used chemotherapeutic drugs for breast cancer; however, its use is limited by drug resistance and side effects. We hypothesized that adding FTY720, a sphingosine-1-phosphate (S1P) receptor functional antagonist, to doxorubicin would potentiate its effects by suppression of drug-induced inflammation.

MATERIALS AND METHODS

The Cancer Genome Atlas, Gene Expression Omnibus data sets, and National Cancer Institute-60 panel were used for gene expressions and gene set enrichment analysis. E0771 syngeneic mammary tumor cells were used. OB/OB mice fed with western high-fat diet were used as an obesity model.

RESULTS

STAT3 expression was significantly increased after doxorubicin treatment in human breast cancer that implicates that doxorubicin evokes inflammation. Expression of sphingosine kinase 1, the enzyme that produces S1P and links inflammation and cancer, tended to be higher in doxorubicin-resistant human cancer and cell lines. In a murine breast cancer model, sphingosine kinase 1, S1P receptor 1, interleukin 6, and STAT3 were overexpressed in the doxorubicin-treated group, whereas all of them were significantly suppressed with addition of FTY720. Combination therapy synergistically suppressed cancer growth both in vitro and in vivo. Furthermore, combination therapy showed higher efficacy in an obesity breast cancer model, where high body mass index demonstrated trends toward worse disease-free and overall survival, and high-serum S1P levels in human patients and volunteers.

CONCLUSIONS

We found that FTY720 enhanced the efficacy of doxorubicin by suppression of drug-induced inflammation, and combination therapy showed stronger effect in obesity-related breast cancer.

Ultrasound imaging of splenomegaly as a proxy to monitor colon tumor development in Apc(min716/+) mice

Animal models of colon cancer are widely used to understand the molecular mechanisms and pathogenesis of the disease. These animal models require a substantial investment of time and traditionally necessitate the killing of the animal to measure the tumor progression. Several in vivo imaging techniques are being used in both human clinics and preclinical studies, albeit at high cost and requiring particular expertise. Here, we report that the progression of splenomegaly coincides with and positively correlates to colon tumor development in Apc^min716/+ mice expressing a mutant gene encoding an adenomatous polyposis coli protein truncated at amino acid 716. Ultrasound image‐based spleen size measurement precisely mirrors splenomegaly development in vivo in the tumor‐laden Apc^min716/+ mice. Moreover, the spleen dimensions extracted from the ultrasound sonograms are positively correlated with normalized spleen weight and the number and area of colon tumors. Hence, we propose measuring the spleen size in vivo by ultrasound imaging as a novel approach to estimate splenomegaly development and to indirectly monitor colon tumor development in Apc^min716/+ mice. The widespread use of ultrasound machines in the laboratory setting, coupled with the fact that it is a noninvasive method, make it a straightforward and useful tool for monitoring the experimental progress of colon cancer in mice and determining end points without killing animals strictly for diagnostics purposes.

Modified breast cancer model for preclinical immunotherapy studies

BACKGROUND

Interest in immunotherapy for breast cancer is rapidly emerging, and applicable animal models that mimic human cancer are urgently needed for preclinical studies. This study aimed to improve a technique for orthotopic inoculation of syngeneic breast cancer cells to be used as a preclinical animal model for immunotherapy.

MATERIALS AND METHODS

We used our previously reported murine model of orthotopic cancer cell inoculation under direct vision and compared the efficiency of tumorigenesis with tumor cells suspended in either phosphate-buffered saline or Matrigel containing varying numbers of cells. As a model for immune rejection, murine BALB/c-derived 4T1-luc2 breast cancer cells were inoculated orthotopically into both BALB/c and C57BL/6 mice.

RESULTS

Matrigel-suspended cells formed larger tumors with higher efficiency than phosphate-buffered saline-suspended cells. The maximum volume of Matrigel that could be inoculated without spillage was 20 μL and 30 μL in the #2 and #4 mammary fat pads, respectively. Tumor take rates increased as the injected cell number increased. In this immune rejection model, there were no significant differences in tumor weight between the strains up to day 7, after which tumor weight decreased in C57BL/6 mice. Bioluminescence in C57BL/6 mice was also significantly less than that in BALB/c mice and increased up to day 7, then swiftly decreased thereafter.

CONCLUSIONS

This improved technique of innoculating murine breast cancer cells using bioluminescence technology may be useful in evaluating the efficacy of tumor regression mediated by immune responses, as shown by an allogeneic response in C57BL/6 mice.

Immune cell interplay in colorectal cancer prognosis

The immune response to colorectal cancer has proven to be a reliable measure of patient outcome in several studies. However, the complexity of the immune response in this disease is not well understood, particularly the interactions between tumour-associated cells and cells of the innate and adaptive immune system. This review will discuss the relationship between cancer associated fibroblasts and macrophages, as well as between macrophages and T cells, and demonstrate how each population may support or prevent tumour growth in a different immune environment.