Diffusion-weighted MRI and 18F-FDG PET correlation with immunity in early radiotherapy response in BNL hepatocellular carcinoma mouse model: timeline validation

Feasibility study of multimodal imaging for redox status and glucose metabolism in tumor

Understanding the tumor redox status is important for efficient cancer treatment. Here, we noninvasively detected changes in the redox environment of tumors before and after cancer treatment in the same individuals using a novel compact and portable electron paramagnetic resonance imaging (EPRI) device and compared the results with glycolytic information obtained through autoradiography using 2-deoxy-2-[18F]fluoro-d-glucose ([18F]FDG). Human colon cancer HCT116 xenografts were used in the mice. We used 3-carbamoyl-PROXYL (3CP) as a paramagnetic and redox status probe for the EPRI of tumors. The first EPRI was followed by the intraperitoneal administration of buthionine sulfoximine (BSO), an inhibitor of glutathione synthesis, or X-ray irradiation of the tumor. A second EPRI was performed on the following day. Autoradiography was performed after the second EPRI. After imaging, the tumor sections were evaluated by histological analysis and the amount of reducing substances in the tumor was measured. BSO treatment and X-ray irradiation significantly decreased the rate of 3CP reduction in tumors. Redox maps of tumors obtained from EPRI can be compared with tissue sections of approximately the same cross section. BSO treatment reduced glutathione levels in tumors, whereas X-ray irradiation did not alter the levels of any of the reducing substances. Comparison of the redox map with the autoradiography of [18F]FDG revealed that regions with high reducing power in the tumor were active in glucose metabolism; however, this correlation disappeared after X-ray irradiation. These results suggest that the novel compact and portable EPRI device is suitable for multimodal imaging, which can be used to study tumor redox status and therapeutic efficacy in cancer, and for combined analysis with other imaging modalities.

Glycolytic Plasticity of Metastatic Lung Cancer Captured by Noninvasive 18F-FDG PET/CT and Serum 1H-NMR Analysis: An Orthotopic Murine Model Study

We aim to establish a noninvasive diagnostic platform to capture early phenotypic transformation for metastasis using 18F-FDG PET and 1H-NMR-based serum metabolomics. Mice with implantation of NCI-H460 cells grew only primary lung tumors in the localized group and had both primary and metastatic lung tumors in the metastatic group. The serum metabolites were analyzed using 1H-NMR at the time of PET/CT scan. The glycolysis status and cell proliferation were validated by Western blotting and staining. A receiver operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic accuracy of SUVmean and serum metabolites in metastasis. In the metastatic mice, the SUVmean of metastatic tumors was significantly higher than that of primary lung tumors in PET images, which was supported by elevated glycolytic protein expression of HK2 and PKM2. The serum pyruvate level in the metastatic group was significantly lower than that in the localized group, corresponding to increased pyruvate-catalyzed enzyme and proliferation rates in metastatic tumors. In diagnosing localized or metastatic tumors, the areas under the ROC curves of SUVmean and pyruvate were 0.92 and 0.91, respectively, with p < 0.05. In conclusion, the combination of 18F-FDG PET and 1H-NMR-based serum metabolomics demonstrated the feasibility of a glycolytic platform for diagnosing metastatic lung cancers.

Multimodal Imaging Response after the Singular or Combination Treatments of Vascular Endothelial Growth Factor Inhibitor and Immune Checkpoint Inhibitor

This study aims to dynamically assess tumor changes after variable treatments with vascular endothelial growth factor (VEGF) inhibitor and/or immune checkpoint inhibitor (ICI) using multimodal imaging of MRI and ¹⁸F-FDG PET/CT in a hepatocellular carcinoma (HCC) mice model. Based on different treatments, 24 mice were randomly divided into four groups: control (isotype-matched IgG antibody 10 mg/kg), VEGF inhibitor (sorafenib 50 mg/kg), ICI (anti-PD-L1 antibody 10 mg/kg), and combination groups (sorafenib 50 mg/kg + anti-PD-L1 antibody 10 mg/kg). Quantitative imaging assessments, including volume transfer constant (K^trans), apparent diffusion coefficient (ADC), lactate/choline ratio, and the maximum standardized ¹⁸F-FDG uptake value ratio of tumor to muscle (SUV_tumor/SUV_muscle ratio), were acquired at different time points (before treatment and 7, 14, and 21 days after treatment). Quantitative data were presented as the mean ± standard errors and two-way repeated-measure ANOVA tests were performed for intergroup and intertime point comparisons. After 21 days from the initiation of therapies, combination group showed the lowest tumor volume and weight, followed by ICI, VEGF inhibitor, and control group, with no significance between the VEGF inhibitor and control groups. In addition, K^trans values significantly decreased, and the lactate/choline ratio and SUV_tumor/SUV_muscle ratio were significantly elevated in the VEGF inhibitor group. ADC significantly increased in the ICI and combination groups, with no significant differences in ADC observed between the control and VEGF inhibitor groups, which showed a similar dynamic change to the tumor volume. Furthermore, K^trans, lactate/choline ratio, and ADC were significantly correlated with CD31⁺ area, hypoxyprobe⁺ area, and apoptosis, respectively. Our results suggest that the singular treatment and combination of the VEGF inhibitor and ICI treatments for HCC present different multimodal imaging changes in accordance with the specific histopathological features. These findings might facilitate the formulation of better treatment response criteria; besides, we find ADC is probably an indicator easily to obtain for treatment response evaluation.

Crosstalk between tumor-associated macrophages and neighboring cells in hepatocellular carcinoma

The tumor microenvironment generally shows a substantial immunosuppressive activity in hepatocellular carcinoma (HCC), accounting for the suboptimal efficacy of immune-based treatments for this difficult-to-treat cancer. The crosstalk between tumor cells and various cell types in the tumor microenvironment is strongly related to HCC progression and treatment resistance. Monocytes are recruited to the HCC tumor microenvironment by various factors and become tumor-associated macrophages (TAMs) with distinct phenotypes. TAMs often contribute to weakened tumor-specific immune responses and a more aggressive phenotype of malignancy. Recent single-cell RNA-sequencing data have demonstrated the central roles of specific TAMs in tumorigenesis and treatment resistance by their interactions with various cell populations in the HCC tumor microenvironment. This review focuses on the roles of TAMs and the crosstalk between TAMs and neighboring cell types in the HCC tumor microenvironment.

Tumor-Associated Macrophages in Hepatocellular Carcinoma: Friend or Foe?

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide, and it has diverse etiologies with multiple mechanisms. The diagnosis of HCC typically occurs at advanced stages when there are limited therapeutic options. Hepatocarcinogenesis is considered a multistep process, and hepatic macrophages play a critical role in the inflammatory process leading to HCC. Emerging evidence has shown that tumor-associated macrophages (TAMs) are crucial components defining the HCC immune microenvironment and represent an appealing option for disrupting the formation and development of HCC. In this review, we summarize the current knowledge of the polarization and function of TAMs in the pathogenesis of HCC, as well as the mechanisms underlying TAM-related anti-HCC therapies. Eventually, novel insights into these important aspects of TAMs and their roles in the HCC microenvironment might lead to promising TAM-focused therapeutic strategies for HCC.

Blocking the CCL5-CCR5 Axis Using Maraviroc Promotes M1 Polarization of Macrophages Cocultured with Irradiated Hepatoma Cells

Purpose

The C-C chemokine ligand 5 (CCL5)–C-C chemokine receptor (CCR5) axis facilitates tumor progression via multiple mechanisms. Herein, we elucidated the effect of a CCR5 antagonist (maraviroc [MVC]; blocking the CCL5–CCR5 axis) on the phenotype of macrophages cocultured with irradiated hepatoma cells. In addition, we investigated whether modulation of macrophage polarization can alter tumor cell sensitivity to radiation.

Materials and Methods

Quantitative reverse-transcription polymerase chain reaction, Western blotting, and enzyme-linked immunosorbent assays were applied to examine the levels of macrophage-associated markers. The mechanisms of macrophage polarization were explored by Western blotting in an in vitro model of coculture of human hepatoma cells with macrophages. The radiation sensitivity was examined in a clonogenic radiosensitivity assay. Tumor cell apoptosis was detected by Western blotting and flow cytometry. A mouse model of a subcutaneous tumor was also established.

Results

CCL5 skewed THP-1 M0 macrophages toward an M2-like phenotype. In coculture with hepatoma cells, macrophages manifested high levels of interleukin (IL) 10, IL-12, tumor necrosis factor α (TNF-α), transforming growth factor β1 (TGF-β1), arginase 1 (ARG1), and IL-1β. Tumor cell irradiation further upregulated these markers in macrophages. After incubation of macrophages with MVC for 24 h, levels of M1 cytokines significantly increased, whereas those of M2 phenotype factors ARG1, TGF-β1, and IL-10 decreased, accompanied by the activation of signal transducer and activator of transcription 3 (STAT3) and downregulation of suppressor of cytokine signaling 3 (SOCS3). The macrophage phenotype reverted to M2 states after treatment with a STAT3 inhibitor. The shift of macrophages toward the M1 phenotype enhanced the radiosensitivity and apoptosis of hepatoma cells. Mice receiving a combination of X-ray irradiation and MVC experienced a better antitumor effect than those receiving either MVC or irradiation alone did.

Conclusion

M2 polarization of macrophages induced by CCL5–CCR5 signaling can be inhibited using MVC via the STAT3–SOCS3 pathway. The shift of macrophages toward the M1 phenotype promotes the sensitivity of human hepatoma cells to X-ray irradiation.

Radiation-Induced Metabolic Shifts in the Hepatic Parenchyma: Findings from 18F-FDG PET Imaging and Tissue NMR Metabolomics in a Mouse Model for Hepatocellular Carcinoma

Purpose: By taking advantage of 18F-FDG PET imaging and tissue nuclear magnetic resonance (NMR) metabolomics, we examined the dynamic metabolic alterations induced by liver irradiation in a mouse model for hepatocellular carcinoma (HCC). Methods: After orthotopic implantation with the mouse liver cancer BNL cells in the right hepatic lobe, animals were divided into two experimental groups. The first received irradiation (RT) at 15 Gy, while the second (no-RT) did not. Intergroup comparisons over time were performed, in terms of 18F-FDG PET findings, NMR metabolomics results, and the expression of genes involved in inflammation and glucose metabolism. Results: As of day one post-irradiation, mice in the RT group showed an increased 18F-FDG uptake in the right liver parenchyma compared with the no-RT group. However, the difference reached statistical significance only on the third post-irradiation day. NMR metabolomics revealed that glucose concentrations peaked on day one post-irradiation both, in the right and left lobes—the latter reflecting a bystander effect. Increased pyruvate and glutamate levels were also evident in the right liver on the third post-irradiation day. The expression levels of the glucose-6-phosphatase (G6PC) and fructose-1, 6-bisphosphatase 1 (FBP1) genes were down-regulated on the first and third post-irradiation days, respectively. Therefore, liver irradiation was associated with a metabolic shift from an impaired gluconeogenesis to an enhanced glycolysis from the first to the third post-irradiation day. Conclusion: Radiation-induced metabolic alterations in the liver parenchyma occur as early as the first post-irradiation day and show dynamic changes over time.

Preclinical Applications of Multi-Platform Imaging in Animal Models of Cancer

In animal models of cancer, oncologic imaging has evolved from a simple assessment of tumor location and size to sophisticated multimodality exploration of molecular, physiologic, genetic, immunologic, and biochemical events at microscopic to macroscopic levels, performed noninvasively and sometimes in real time. Here, we briefly review animal imaging technology and molecular imaging probes together with selected applications from recent literature. Fast and sensitive optical imaging is primarily used to track luciferase-expressing tumor cells, image molecular targets with fluorescence probes, and to report on metabolic and physiologic phenotypes using smart switchable luminescent probes. MicroPET/single-photon emission CT have proven to be two of the most translational modalities for molecular and metabolic imaging of cancers: immuno-PET is a promising and rapidly evolving area of imaging research. Sophisticated MRI techniques provide high-resolution images of small metastases, tumor inflammation, perfusion, oxygenation, and acidity. Disseminated tumors to the bone and lung are easily detected by microCT, while ultrasound provides real-time visualization of tumor vasculature and perfusion. Recently available photoacoustic imaging provides real-time evaluation of vascular patency, oxygenation, and nanoparticle distributions. New hybrid instruments, such as PET-MRI, promise more convenient combination of the capabilities of each modality, enabling enhanced research efficacy and throughput.

MR-Guided Radiotherapy: The Perfect Partner for Immunotherapy?

During the last years, preclinical and clinical studies have emerged supporting the rationale to integrate radiotherapy and immunotherapy. Radiotherapy may enhance the effects of immunotherapy by improving tumor antigen release, antigen presentation, and T-cell infiltration. Recently, magnetic resonance guided radiotherapy (MRgRT) has become clinically available. Compared to conventional radiotherapy techniques, MRgRT firstly allows for daily on-table treatment adaptation, which enables both dose escalation for increasing tumor response and superior sparing of radiosensitive organs-at-risk for reducing toxicity. The current review focuses on the potential of combining MR-guided adaptive radiotherapy with immunotherapy by providing an overview on the current status of MRgRT, latest developments in preclinical and clinical radio-immunotherapy, and the unique opportunities and challenges for MR-guided radio-immunotherapy. MRgRT might especially assist in answering open questions in radio-immunotherapy regarding optimal radiation dose, fractionation, timing of immunotherapy, appropriate irradiation volumes, and response prediction.