The low overall survival rate of patients with pancreatic cancer has driven research to seek a new therapeutic protocol. Radiotherapy (RT) is frequently an option in the neoadjuvant or palliative settings for pancreatic cancer treatment. This study explored the effect of RT protocols on the tumor microenvironment (TME) and their consequent impact on anti-programmed cell death ligand-1 (PD-L1) therapy. Using a murine orthotopic pancreatic tumor model, UN-KC-6141, RT-disturbed TME was examined by immunohistochemical staining. The results showed that ablative RT is more effective than fractionated RT at recruiting T cells. On the other hand, fractionated RT induces more myeloid-derived suppressor cell infiltration than ablative RT. The RT-disturbed TME presents a higher perfusion rate per vessel. The increase in vessel perfusion is associated with a higher amount of anti-PD-L1 antibody being delivered to the tumor. Animal survival is increased by anti-PD-L1 therapy after ablative RT, with 67% of treated animals surviving more than 30 days after tumor inoculation compared to a median survival time of 16.5 days for the control group. Splenocytes isolated from surviving animals were specifically cytotoxic for UN-KC-6141 cells. We conclude that the ablative RT-induced TME is more suited than conventional RT-induced TME to combination therapy with immune checkpoint blockade.

Radiation therapy (RT) recruits myeloid cells, leading to an immunosuppressive microenvironment that impedes its efficacy against tumors. Combination of immunotherapy with RT is a potential approach to reversing the immunosuppressive condition and enhancing tumor control after RT. This study aimed to assess the effects of local interleukin-12 (IL-12) therapy on improving the efficacy of RT in a murine prostate cancer model. Combined treatment effectively shrunk the radioresistant tumors by inducing a T helper-1 immune response and influx of CD8+ T cells. It also delayed the radiation-induced vascular damage accompanied by increased α-smooth muscle actin-positive pericyte coverage and blood perfusion. Moreover, RT significantly reduced the IL-12-induced levels of alanine aminotransferase in blood. However, it did not further improve the IL-12-induced anti-tumor effect on distant tumors. Upregulated expression of T-cell exhaustion-associated genes was found in tumors treated with IL-12 only and combined treatment, suggesting that T-cell exhaustion is potentially correlated with tumor relapse in combined treatment. In conclusion, this study illustrated that combination of radiation and local IL-12 therapy enhanced the host immune response and promoted vascular maturation and function. Furthermore, combination treatment was associated with less systemic toxicity than IL-12 alone, providing a potential option for tumor therapy in clinical settings.

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.

Previous studies revealed that tumor-associated macrophages/microglia (TAMs) promoted glioma invasiveness during tumor progression and after radiotherapy. However, the communication of TAMs with tumor cells remains unclear. This study aimed to examine the role of small extracellular vesicles (sEVs) derived from TAMs in TAMs-mediated brain tumor invasion. This study utilized BV2 and RAW264.7 cell lines representing resident and infiltrating macrophages, respectively, to unveil their effect on tumor cells. Purified sEVs from BV2 and RAW264.7 were validated by nanoparticle track analysis (NTA), transmission electron microscopy (TEM), and western blotting for sEV markers. The effect of sEVs on the murine astrocytoma tumor cell line ALTS1C1 was examined on cell proliferation, migration, and gene expression. The results showed that ALTS1C1 cells effectively engulfed sEVs purified from BV2 and RAW264.7. Only BV2-derived sEVs promoted cell proliferation and were dose-dependent. Further, morphological changes in ALTS1C1 cells were observed after incubation with BV2-derived sEVs, which was associated with enhancing cell migration. BV2-mediated glioma proliferation and mobility were related to the upregulation of vascular endothelial growth factor (VEGF) and downregulation of death effector domain-containing protein (DEDD) gene expression. This study demonstrates the distinct function of sEVs of resident macrophages on glioma cell invasion and reveals the mechanism underlying microglia-mediated tumor progression. These findings suggested resident microglia is the potential therapeutic target for TAMs-induced brain tumor invasiveness.

Proton beam therapy is an advanced treatment for patients with unresectable hepatocellular carcinoma. However, evaluating the response to treatment with tumor size alone is insufficient. Herein, we used kinetic [18F]-FDG PET and diffusion-weighted MR imaging to monitor the biological responses to proton beam therapy in hepatocellular carcinoma mice to assess treatment efficacy. Murine BNL HCC cells were orthotopically implanted into the livers of 8-week-old male BALB/c mice, which received 20 Gy of the single dose in proton beam therapy. The biological responses to proton beam therapy were assessed on pre-treatment and post-treatment days 1, 3, and 7. Compared with the not-receiving proton beam therapy group, the treated group led to an increasing trend in tumor K1 values and constant relative SUVs within 7 days on the dynamic PET imaging. On diffusion-weighted MR imaging, the tumor relative apparent diffusion coefficient values significantly increased post-treatment days 3 and 7. Significantly decreased tumor proliferation, cellular density, and cellular uptake of [18F]-FDG on days 1 and/or 3 post-treatment, with a rebound on day 7, were observed in the dynamic profiling of tumor cells ex vivo and in vitro. Vascular remodeling and elevated macrophage infiltrates in the tumor microenvironment were associated with proton beam therapy. However, there were no significant changes in tumor size between the treated and non-treated groups after treatment until day 7. In vivo kinetic [18F]-FDG PET/MRI techniques can provide a feasible means to assess early liver tumor response to proton beam therapy and predict treatment outcomes.

Radiation therapy for liver and upper abdominal malignancies is associated with a high risk of radiation-induced liver disease (RILD), often involving metabolic disturbances. This study aimed to characterize metabolomic alterations in a murine RILD model using ¹H-nuclear magnetic resonance (NMR) spectroscopy. RILD was induced in mice via 15 Gy hepatic irradiation. Liver tissues were subjected to time-course metabolomic profiling using ¹H NMR. Validation was performed through liver enzyme assays, histological analysis, and qPCR. Taurine was selected for therapeutic evaluation based on metabolomic findings. Significant reductions in glutathione and pyruvate levels were observed in the acute stage, whereas increases in phenylalanine and tyrosine levels were observed in the chronic stage. These metabolite alterations were correlated with reactive oxygen species (ROS) production, glycolysis modulation, and fibrosis progression in RILD. Notably, taurine levels increased during the acute stage but decreased during the chronic stage. Furthermore, in mice at 12 weeks postirradiation, taurine supplementation maintained liver enzyme activity, cytokine profiles, and taurine metabolism at levels similar to those of the control group. In conclusion, this study revealed dynamic metabolic changes associated with physiological alterations in a murine RILD model and identified, through ¹H NMR metabolomics, taurine as a potential target for alleviating nonclassical RILD symptoms.