Bioluminescence Imaging for Evaluation of Antitumor Effect In Vitro and In Vivo in Mice Xenografted Tumor Models

Photoinduced Actin Aggregation Involves Cell Death: A Mechanism of Cancer Cell Cytotoxicity after Near-Infrared Photoimmunotherapy

Near-infrared photoimmunotherapy (NIR-PIT) is a cancer treatment modality that uses antibody-photoabsorber (IR700) conjugates to destroy specific cells. The reaction between the antibody and photoabsorber is triggered by NIR-light, and this alters the shape and hydrophilicity of the conjugate. This photochemical reaction is responsible for NIR-PIT-induced cell death; however, the detailed mechanism underlying this effect remains unknown. In this study, we demonstrated that actin filaments underneath the cell membrane play an important role in NIR-PIT-induced cell death and that IR700 mediates the photochemical reaction of the conjugates, leading to actin filament aggregation upon NIR-light irradiation. The destruction of cortical actin beneath the cell plasma membrane allows water to flow into the cell based on osmotic conditions, resulting in cell rupture. This sequence of events may constitute the mechanism of NIR-PIT-induced cell death, making NIR-PIT a promising cancer treatment modality.

Protocol for the development of a bioluminescent AML-PDX mouse model for the evaluation of CAR T cell therapy

Patient-derived xenograft (PDX) models of acute myeloid leukemia (AML-PDX) offer advantages over cell line models by capturing the complexity and heterogeneity of patient-derived samples. Here, we present a protocol for developing a bioluminescent AML-PDX model in mice to evaluate chimeric antigen receptor (CAR) T cell therapy. We describe steps for transducing, engrafting, expanding, and enriching AML-PDX cells. We then detail procedures for in vitro and in vivo validation of the AML-PDX model for the evaluation of CAR T cell immunotherapy. For complete details on the use and execution of this protocol, please refer to Caulier et al.1.

KPC-luciferase-expressing cells elicit an anti-tumor immune response in a mouse model of pancreatic cancer

Mouse models for the study of pancreatic ductal adenocarcinoma (PDAC) are well-established and representative of many key features observed in human PDAC. To monitor tumor growth, cancer cells that are implanted in mice are often transfected with reporter genes, such as firefly luciferase (Luc), enabling in vivo optical imaging over time. Since Luc can induce an immune response, we aimed to evaluate whether the expression of Luc could affect the growth of KPC tumors in mice by inducing immunogenicity. Although both cell lines, KPC and Luc transduced KPC (KPC-Luc), had the same proliferation rate, KPC-Luc tumors had significantly smaller sizes or were absent 13 days after orthotopic cell implantation, compared to KPC tumors. This coincided with the loss of bioluminescence signal over the tumor region. Immunophenotyping of blood and spleen from KPC-Luc tumor-bearing mice showed a decreased number of macrophages and CD4+ T cells, and an increased accumulation of natural killer (NK) cells in comparison to KPC tumor mice. Higher infiltration of CD8+ T cells was found in KPC-Luc tumors than in their controls. Moreover, the immune response against Luc peptide was stronger in splenocytes from mice implanted with KPC-Luc cells compared to those isolated from KPC wild-type mice, indicating increased immunogenicity elicited by the presence of Luc in the PDAC tumor cells. These results must be considered when evaluating the efficacy of anti-cancer therapies including immunotherapies in immunocompetent PDAC or other cancer mouse models that use Luc as a reporter for bioluminescence imaging.

Contrast-enhanced ultrasound imaging for monitoring the efficacy of near-infrared photoimmunotherapy

BACKGROUND

Near-infrared photoimmunotherapy (NIR-PIT) is a promising cancer therapy combining NIR-light irradiation with an antibody and IR700DX, a light-sensitive substance, to destroy tumours. However, homogeneous irradiation is difficult because the light varies depending on the distance and tissue environment. Therefore, markers that indicate sufficient irradiation are necessary. Nanoparticles sized 10∼200 nm show enhanced permeation and retention within tumours, which is further enhanced via NIR-PIT (super enhanced permeability and retention, SUPR). We aimed to monitor the effectiveness of NIR-PIT by measuring SUPR.

METHODS

A xenograft mouse tumour model was established by inoculating human cancer cells in both buttocks of Balb/C-nu/nu mice, and NIR-PIT was performed on only one side. To evaluate SUPR, fluorescent signal examination was performed using QD800-fluorescent nanoparticles and NIR-fluorescent poly (d,l-lactide-co-glycolic acid) (NIR-PLGA) microparticles. Harmonic signals were evaluated using micro-bubbles of the contrast agent Sonazoid and contrast-enhanced ultrasound (CEUS) imaging. The correlation between SUPR immediately after treatment and NIR-PIT effectiveness on the day after treatment was evaluated.

FINDINGS

QD800 fluorescent signals persisted only in the treated tumours, and the intensity of remaining signals showed high positive correlation with the therapeutic effect. NIR-PLGA fluorescent signals and Sonazoid-derived harmonic signals remained for a longer time in the treated tumours than in the controls, and the kE value of the two-compartment model correlated with NIR-PIT effectiveness.

INTERPRETATION

SUPR measurement using Sonazoid and CEUS imaging could be easily adapted for clinical use as a therapeutic image-based biomarker for monitoring and confirming of NIR-PIT efficacy.

FUNDING

This research was supported by ARIM JAPAN of MEXT, the Program for Developing Next-generation Researchers (Japan Science and Technology Agency), KAKEN (18K15923, 21K07217) (JSPS), CREST (JPMJCR19H2, JST), and FOREST-Souhatsu (JST). Mochida Memorial Foundation for Medical and Pharmaceutical Research; Takeda Science Foundation; The Japan Health Foundation; and Princess Takamatsu Cancer Research Fund. Funders only provided financial support and had no role in the study design, data collection, data analysis, interpretation, and writing of the report.

Towards an optimal model for gastric cancer peritoneal metastasis: current challenges and future directions

Peritoneal metastasis is a challenging aspect of clinical practice for gastric cancer. Animal models are crucial in understanding molecular mechanisms, assessing drug efficacy, and conducting clinical intervention studies, including those related to gastric cancer peritoneal metastasis. Unlike other xenograft models, peritoneal metastasis models should not only present tumor growth at the transplant site, but also recapitulate tumor cell metastasis in the abdominal cavity. Developing a reliable model of gastric cancer peritoneal metastasis involves several technical aspects, such as the selection of model animals, source of xenograft tumors, technology of transplantation, and dynamic monitoring of the tumor progression. To date, challenges remain in developing a reliable model that can completely recapitulate peritoneal metastasis. Thus, this review aims to summarize the techniques and strategies used to establish animal models of gastric cancer peritoneal metastasis, providing a reference for future model establishment.

Fluorescent Organic Small Molecule Probes for Bioimaging and Detection Applications

The activity levels of key substances (metal ions, reactive oxygen species, reactive nitrogen, biological small molecules, etc.) in organisms are closely related to intracellular redox reactions, disease occurrence and treatment, as well as drug absorption and distribution. Fluorescence imaging technology provides a visual tool for medicine, showing great potential in the fields of molecular biology, cellular immunology and oncology. In recent years, organic fluorescent probes have attracted much attention in the bioanalytical field. Among various organic fluorescent probes, fluorescent organic small molecule probes (FOSMPs) have become a research hotspot due to their excellent physicochemical properties, such as good photostability, high spatial and temporal resolution, as well as excellent biocompatibility. FOSMPs have proved to be suitable for in vivo bioimaging and detection. On the basis of the introduction of several primary fluorescence mechanisms, the latest progress of FOSMPs in the applications of bioimaging and detection is comprehensively reviewed. Following this, the preparation and application of fluorescent organic nanoparticles (FONPs) that are designed with FOSMPs as fluorophores are overviewed. Additionally, the prospects of FOSMPs in bioimaging and detection are discussed.