tumor-hypoxia-assessment-vivo-3d-oxygen-imaging-through-electron

Tumor Hypoxia Assessment: In Vivo 3D Oxygen Imaging Through Electron Paramagnetic Resonance

The precise and real-time measurement of oxygen partial pressure (pO2) brings valuable information in many pathologies, including cancer. Low tumor pO2 ...

Jagiellonian University

Low tissue oxygenation significantly impairs the effectiveness of cancer therapy and promotes a more aggressive phenotype. Many strategies to improve tissue oxygenation have been proposed throughout the years, but only a few showed significant effects in clinical settings. We investigated stability and ultrasound pulse (UP) triggered oxygen release from phospholipid coated oxygen microbubbles (OMB) in vitro and in murine tumors in vivo using EPR oximetry. In solution, the investigated microbubbles are stable and responsive to ultrasound pulse. The addition of the OMB solution alone resulted in an increase in pO of approximately 70 mmHg which was further increased for an additional 80 mmHg after the application of UP. The in vivo kinetic study revealed a substantial, up to 120 mmHg, increase in tumor pO after UP application and then pO was decreasing for 20 min for intravenous injection and 15 min for intratumoral injection. A significant increase was also observed in groups that received microbubbles filled with nitrogen and ultrasound pulse and OMB without UP, but the effect was much lower. Oxygen microbubbles lead to a decrease in HIF-1a and VEGF-A both at the level of mRNA and protein. Toxicity analysis showed that intravenous injection of OMB does not cause oxidative damage to the heart, liver, or kidneys. However, elevated levels of oxidative damage to lipids and proteins were observed short-term in tumor tissue. In conclusion, we have demonstrated the feasibility of oxygen microbubbles in delivering oxygen effectively and safely to the tumor in living animals. Such treatment might enhance the effectiveness of other anticancer therapies.

Increasing oxygen tension in tumor tissue using ultrasound sensitive O microbubbles.

The inadequate level of oxygenation in tumors has been shown to correlate not only with greater invasiveness of cancer cells, but also with a reduction in their sensitivity to anticancer therapies. Over the years, many attempts have been made to increase the oxygenation level of cancer, but most of them have been ineffective. We investigated the heterogeneous response of tumor tissue to phospholipid-coated oxygen microbubbles (OMB) in murine tumors in vivo using oxygen and hemoglobin saturation mapping and the influence of OMB treatment on microvasculature, perfusion, and radiotherapy effectiveness. Intravenous administration of OMB followed by ultrasound pulse leads to increased oxygenation of a tumor, found mainly in the vicinity of tumor vessels, while intratumoral delivery resulted in areas of increased pO more evenly distributed within the tumor. Furthermore, hemoglobin contributes little to the increase in tumor oxygenation caused by oxygen microbubbles. Extensive vasculature disruption was observed in the groups treated with both oxygen/nitrogen microbubbles and ultrasound pulse. This therapy also led to a reduction in the coverage of the vessels by pericytes, while the density of the microvessels was unchanged. Radiotherapy with a single dose of 12Gy reduced tumor growth by 50% in all treated groups. Unfortunately, at the same time, the number of macroscopic metastases in the lungs increased significantly after intravenous administration of oxygen/nitrogen microbubbles and the application of an ultrasound pulse. In conclusion, ultrasound-sensitive oxygen microbubbles are effective in delivering oxygen to tumor tissue, thus increasing the effectiveness of radiotherapy. However, cavitation effects and destruction of the integrity of tumor vessels result in greater spread of cancer cells in the host organism.

Ultrasound sensitive O microbubbles radiosensitize murine breast cancer but lead to higher metastatic spread.

Radiotherapy is a cornerstone of cancer treatment, but tumor hypoxia and resistance to radiation remain significant challenges. Vascular normalization has emerged as a strategy to improve oxygenation and enhance therapeutic outcomes. In this study, we examine the radiosensitization potential of vascular normalization using metformin, a widely used anti-diabetic drug, and oxygen microbubbles (OMBs). We investigated the synergistic action of metformin and OMBs and the impact of this therapeutic combination on the vasculature, oxygenation, invasiveness, and radiosensitivity of murine 4T1 breast cancer. We employed in vivo Doppler ultrasonographic imaging for vasculature analysis, electron paramagnetic resonance oximetry, and immunohistochemical assessment of microvessels, perfusion, and invasiveness markers. Our findings demonstrate that both two-week metformin therapy and oxygen microbubble treatment normalize abnormal cancer vasculature. The combination of metformin and OMB yielded more pronounced and sustained effects than either treatment alone. The investigated therapy protocols led to nearly twice the radiosensitivity of 4T1 tumors; however, no significant differences in radiosensitivity were observed between the various treatment groups. Despite these improvements, resistance to treatment inevitably emerged, leading to the recurrence of hypoxia and an increased incidence of metastasis.

Murine Breast Cancer Radiosensitization Using Oxygen Microbubbles and Metformin: Vessels Are the Key.

The goal of this work was to compare pO measured using both continuous wave (CW) and pulse electron paramagnetic resonance (EPR) spectroscopy. The Oxychip particle spin probe enabled longitudinal monitoring of pO in murine pancreatic tumor treated with gemcitabine during the course of therapy.

Article	Year
Increasing oxygen tension in tumor tissue using ultrasound sensitive O microbubbles. Free radical biology & medicine\| PubMed ID: 36356713	2022
Ultrasound sensitive O microbubbles radiosensitize murine breast cancer but lead to higher metastatic spread. Free radical biology & medicine\| PubMed ID: 36858326	2023
Murine Breast Cancer Radiosensitization Using Oxygen Microbubbles and Metformin: Vessels Are the Key. International journal of molecular sciences\| PubMed ID: 37569531	2023
Pulse and CW EPR Oximetry Using Oxychip in Gemcitabine-Treated Murine Pancreatic Tumors. Molecular imaging and biology\| PubMed ID: 37784004	2024

Gabriela Dziurman

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