Comparison of implantation sites for the development of peritoneal metastasis in a colorectal cancer mouse model using non-invasive bioluminescence imaging

Effect of 5-Fluoro-Uracile + Oxaliplatin chemotherapy on the histological response of PEritoneal and hePatIc corectal metasTases in a mOuse model: PEPITO experimental study

BACKGROUND

The histological responses (HRs) after systemic chemotherapy should be used to determine the optimal management of patients with peritoneal and liver metastasis from colorectal cancer (cPM, cLM), in curative intent. We aimed to compare HRs of cPM and cLM in metastatic mice model after chemotherapy.

METHODS

Colon carcinoma CT26-luc cells were transplanted into syngeneic BALB/c mice by intraperitoneal (leading to cPM), intrasplenic (leading to cLM), or intraperitoneal + intrasplenic (leading to cPM cLM) injections and follow up using bioluminescence during 21 days. Bi-chemotherapeutic treatment (5-fluorouracil at D11, D17, and D20, and oxaliplatin at D13 and D19) was administered. The peritoneal cancer index (PCI) and HRs using Peritoneal Regression Grading Score (PRGS) and Tumor Regression Grade (TRG) classifications were analyzed at day 21.

RESULTS

Unlike bioluminescence rate, PCI was reduced after chemotherapy in all treated groups with cPM comparatively to controls (33 ± 9.5 vs. 19.8 ± 5, p = 0.002 for cPM groups; 37.7 ± 3.6 vs. 25.2 ± 10.8, p = 0.0003 for the cPM + cLM groups). The complete or major HR rates were higher in all treated groups compared to the non-treated mice (cPM, 2.29 ± 0.55 vs. 3.56 ± 1.01; cLM, 2.43 ± 1.89 vs. 4.86 ± 0.378; cPM + cLM, 2.73 ± 1.03 and 2.2 ± 0.65 vs. 3.79 ± 0.75 and 4.36 ± 0.43). The complete or major HR rates after chemotherapy were similar across the metastatic sites in 60% for cPM + cLM group.

CONCLUSIONS

The efficacy of chemotherapeutic treatment did not differ between the metastatic sites. Murine models are suitable in histological analyses to study tumor development and regression but clinical study will be performed to confirm these results.

Magnetic Compression of Tumor Spheroids Increases Cell Proliferation In Vitro and Cancer Progression In Vivo

A growing tumor is submitted to ever-evolving mechanical stress. Endoscopic procedures add additional constraints. However, the impact of mechanical forces on cancer progression is still debated. Herein, a set of magnetic methods is proposed to form tumor spheroids and to subject them to remote deformation, mimicking stent-imposed compression. Upon application of a permanent magnet, the magnetic tumor spheroids (formed from colon cancer cells or from glioblastoma cells) are compressed by 50% of their initial diameters. Such significant deformation triggers an increase in the spheroid proliferation for both cell lines, correlated with an increase in the number of proliferating cells toward its center and associated with an overexpression of the matrix metalloproteinase-9 (MMP-9). In vivo peritoneal injection of the spheroids made from colon cancer cells confirmed the increased aggressiveness of the compressed spheroids, with almost a doubling of the peritoneal cancer index (PCI), as compared with non-stimulated spheroids. Moreover, liver metastasis of labeled cells was observed only in animals grafted with stimulated spheroids. Altogether, these results demonstrate that a large compression of tumor spheroids enhances cancer proliferation and metastatic process and could have implications in clinical procedures where tumor compression plays a role.

Adipocytic Glutamine Synthetase Upregulation via Altered Histone Methylation Promotes 5FU Chemoresistance in Peritoneal Carcinomatosis of Colorectal Cancer

The development of resistance to 5-fluorouracil (5FU) chemotherapy is a major handicap for sustained effective treatment in peritoneal carcinomatosis (PC) of colorectal cancer (CRC). Metabolic reprogramming of adipocytes, a component of the tumor microenvironment and the main composition of peritoneum, plays a significant role in drug resistance of PC, with the mechanisms being not fully understood. By performing metabolomics analysis, we identified glutamine (Gln), an important amino acid, inducing resistance to 5FU-triggered tumor suppression of CRC-PC through activating mTOR pathway. Noteworthily, genetic overexpression of glutamine synthetase (GS) in adipocytes increased chemoresistance to 5FU in vitro and in vivo while this effect was reversed by pharmacological blockage of GS. Next, we showed that methionine metabolism were enhanced in amino acid omitted from CRC-PC of GS transgenic (Tg^GS) mice, increasing intracellular levels of S-carboxymethy-L-cys. Moreover, loss of dimethylation at lysine 4 of histone H3 (H3k4me2) was found in adipocytes in vitro, which may lead to increased expression of GS. Furthermore, biochemical inhibition of lysine specific demethylase 1 (LSD1) restored H3k4me2, thereby reducing GS-induced chemoresistance to 5FU. Our findings indicate that GS upregulation-induced excessive of Gln in adipocytes via altered histone methylation is potential mediator of resistance to 5FU chemotherapy in patients with CRC-PC.

Establishment of an In Vivo Xenograft Mouse Model of a Subcutaneous Submillimeter HT-29 Tumor Formed from a Single Spheroid Transplanted Using Radiation-Crosslinked Gelatin Hydrogel Microwell

Colorectal cancer is a frequent cause of death worldwide. The detection and treatment of small nodules are crucial for improving survival of colorectal cancer patients. Submillimeter tumors are useful tools for developing novel methods to approach this issue. However, there are no suitable in vivo models that allow easy monitoring of the growth of these tumors. This study established a xenograft mouse model of subcutaneous submillimeter tumors with human colorectal cancer HT-29 cells. We transplanted a single spheroid formed by HT-29 cells expressing red fluorescent protein (RFP) (HT-29-RFP). Additionally, we adopted our newly developed radiation-crosslinked gelatin hydrogel microwells (rGHMs), which can be used as a culture base to form spheroids and as a transplantation scaffold with biocompatibility and biodegradability. Spheroids approximately 700 μm in size were uniformly created in seven days in the respective rGHMs. Every single spheroid was extracted either with or without rGHM and transplanted into the subcutis of severe combined immunodeficiency (SCID) mice (n = 4). After 21 days, the spheroids inoculated together with rGHM successfully formed uniform subcutaneous submillimeter tumor xenografts that were observable in vivo in a stereoscopic fluorescence microscope in all transplanted mice. In contrast, spheroids transplanted without rGHM also developed small tumors in all mice but showed higher variability in size than those transplanted with rGHM. During transplantation, the rGHM ensured easy handling and stabilization of the position of a single spheroid. Inoculation of spheroids with rGHM in the nude mice was similarly examined (n = 4), showing that only one out of four mice formed tumors. In conclusion, rGHM effectively formed spheroids and created uniformed xenografted submillimeter tumors of HT-29-RFP in SCID mice. Our model could provide a useful platform to develop medicines and methods for detection and treatment of small nodules of colorectal cancer.

Energy status dictates PD-L1 protein abundance and anti-tumor immunity to enable checkpoint blockade

Aberrant energy status contributes to multiple metabolic diseases, including obesity, diabetes, and cancer, but the underlying mechanism remains elusive. Here, we report that ketogenic-diet-induced changes in energy status enhance the efficacy of anti-CTLA-4 immunotherapy by decreasing PD-L1 protein levels and increasing expression of type-I interferon (IFN) and antigen presentation genes. Mechanistically, energy deprivation activates AMP-activated protein kinase (AMPK), which in turn, phosphorylates PD-L1 on Ser283, thereby disrupting its interaction with CMTM4 and subsequently triggering PD-L1 degradation. In addition, AMPK phosphorylates EZH2, which disrupts PRC2 function, leading to enhanced IFNs and antigen presentation gene expression. Through these mechanisms, AMPK agonists or ketogenic diets enhance the efficacy of anti-CTLA-4 immunotherapy and improve the overall survival rate in syngeneic mouse tumor models. Our findings reveal a pivotal role for AMPK in regulating the immune response to immune-checkpoint blockade and advocate for combining ketogenic diets or AMPK agonists with anti-CTLA4 immunotherapy to combat cancer.

CD244+ polymorphonuclear myeloid‑derived suppressor cells reflect the status of peritoneal dissemination in a colon cancer mouse model

Despite the recent development of chemotherapeutic agents, the prognosis of colorectal cancer (CRC) patients with peritoneal dissemination (PD) remains poor. The tumor immune microenvironment (TIME) has drawn attention as a key contributing factor of tumor progression. Of TIME components, myeloid-derived suppressor cells (MDSCs) are considered to play a responsible role in the immunosuppressive characteristics of the TIME. MDSCs are classified into two major subsets: Monocytic MDSCs (M-MDSCs) and polymorphonuclear MDSCs (PMN-MDSCs). Therefore, we hypothesize that MDSCs would play important roles in the PD-relevant TIME and PD progression. To address this hypothesis, we established PD mouse models. As the PD nodules consisted scarcely of immune cells, we focused on the peritoneal cavity, but not PD nodule, to evaluate the PD-relevant TIME. As a result, intraperitoneal PMN-MDSCs were found to be substantially increased in association with PD progression. Based on these results, we phenotypically and functionally verified the usefulness of CD244 for identifying PMN-MDSCs. In addition, the concentrations of interleukin (IL)-6 and granulocyte-colony stimulating factor (G-CSF) were significantly increased in the peritoneal cavity, both of which were produced by the tumors and thought to contribute to the increases in the PMN-MDSCs. In vivo depletion of the PMN-MDSCs by anti-Ly6G monoclonal antibody (mAb) significantly inhibited the PD progression and reverted CD4⁺ and CD8⁺ T cells in the peritoneal cavity and the peripheral blood. Collectively, these results suggest that the targeted therapy for PMN-MDSCs would provide not only new therapeutic value but also a novel strategy to synergize with T-cell-based immunotherapy for CRC-derived PD.

CD31 and D2-40 Contribute to Peritoneal Metastasis of Colorectal Cancer by Promoting Epithelial-Mesenchymal Transition

Background/Aims

Colorectal cancer (CRC) patients often exhibit peritoneal metastasis, which negatively impacts their prognosis. CD31 and D2-40 have recently been suggested to be predictors of breast cancer prognosis, but their role in colorectal peritoneal metastasis (CRPM) remains unknown.

Methods

The expression profiles of CD31 and D2-40 were analyzed in CRC patients with or without CRPM and in CRC cell lines with increasing metastatic potential. Overexpression and short hairpin RNA knockdown assays were performed in CRC cells, and the effects of these alterations on epithelial-mesenchymal transition (EMT) in vitro, growth of xenograft tumors in vivo, and peritoneal metastasis potential in a mouse model of CRPM were examined.

Results

The expressions of CD31 and D2-40 were upregulated in CRC tumor tissues and was elevated further in tumor tissues from patients with CRPM. CD31 and D2-40 expression levels exhibited increasing trends parallel to the EMT potential of CRC cells. CD31 and D2-40 are essential for CRC cell EMT in vitro as well as for xenograft tumor growth and peritoneal metastasis in vivo.

Conclusions

CD31 and D2-40 contribute to CRPM by promoting EMT and may serve as prognostic markers and therapeutic targets for CRC, particularly in patients with peritoneal metastasis.

10 ns PEFs induce a histological response linked to cell death and cytotoxic T-lymphocytes in an immunocompetent mouse model of peritoneal metastasis

PURPOSE

The application of nanosecond pulsed electric fields (nsPEFs) could be an effective therapeutic strategy for peritoneal metastasis (PM) from colorectal cancer (CRC). The aim of this study was to evaluate in vitro the sensitivity of CT-26 CRC cells to nsPEFs in combination with chemotherapeutic agents, and to observe the subsequent in vivo histologic response.

METHODS

In vitro cellular assays were performed to assess the effects of exposure to 1, 10, 100, 500 and 1000 10 ns pulses in a cuvette or bi-electrode system at 10 and 200 Hz. nsPEF treatment was applied alone or in combination with oxaliplatin and mitomycin. Cell death was detected by flow cytometry, and permeabilization and intracellular calcium levels by fluorescent confocal microscopy after treatment. A mouse model of PM was used to investigate the effects of in vivo exposure to pulses delivered using a bi-electrode system; morphological changes in mitochondria were assessed by electron microscopy. Fibrosis was measured by multiphoton microscopy, while the histological response (HR; hematoxylin-eosin-safran stain), proliferation (KI67, DAPI), and expression of immunological factors (CD3, CD4, CD8) were evaluated by classic histology.

RESULTS

10 ns PEFs exerted a dose-dependent effect on CT-26 cells in vitro and in vivo, by inducing cell death and altering mitochondrial morphology after plasma membrane permeabilization. In vivo results indicated a specific CD8+ T cell immune response, together with a strong HR according to the Peritoneal Regression Grading Score (PRGS).

CONCLUSIONS

The effects of nsPEFs on CT-26 were confirmed in a mouse model of CRC with PM.

Mouse Models of Peritoneal Carcinomatosis to Develop Clinical Applications

Simple Summary

Peritoneal carcinomatosis mouse models as a platform to test, improve and/or predict the appropriate therapeutic interventions in patients are crucial to providing medical advances. Here, we overview reported mouse models to explore peritoneal carcinomatosis in translational biomedical research.

Abstract

Peritoneal carcinomatosis of primary tumors originating in gastrointestinal (e.g., colorectal cancer, gastric cancer) or gynecologic (e.g., ovarian cancer) malignancies is a widespread type of tumor dissemination in the peritoneal cavity for which few therapeutic options are available. Therefore, reliable preclinical models are crucial for research and development of efficacious treatments for this condition. To date, a number of animal models have attempted to reproduce as accurately as possible the complexity of the tumor microenvironment of human peritoneal carcinomatosis. These include: Syngeneic tumor cell lines, human xenografts, patient-derived xenografts, genetically induced tumors, and 3D scaffold biomimetics. Each experimental model has its own strengths and limitations, all of which can influence the subsequent translational results concerning anticancer and immunomodulatory drugs under exploration. This review highlights the current status of peritoneal carcinomatosis mouse models for preclinical development of anticancer drugs or immunotherapeutic agents.