Partial pressure of oxygen monitoring based on EPR in chemotherapy for breast cancer and its mechanism / 肿瘤

ABSTRACT

Objective: The level of partial pressure of oxygen (PO2) in tumor microenvironment affects the tumor's sensitivity to chemothropy directly. Oxygen measuring technique from electron paramagnetic resonance (EPR) can offer the necessary technical to monitor the change of the PO2 in tumor microenvironment after chemothrapy uninvasively, real-time and accurately. Methods: EPR was used to measure the PO2 level directly in vivo. Tumor tissue was collected and the activity of mitochondria was assayed through kinetics of enzyme-catalyzed reactions. The laser doppler monitor was used to detect regional blood flow. Results: The data from the test of tissue oximetry demonstrated the initial PO2 in tumor microenvironment gradually increased to peak value at the fourth week, which was significant higher than initial PO2 of tumor. The PO2 was higher in the experimental group after administration of doxorubicin (ADM). Then PO2 was gradually declined. The functions of mitochondrial nicotinamide adenine dinucleotide reduced dehydragenale, cytochrome C oxidase and succinate-cytochrome C reductase in tumor tissue were lower than those of the control group on the 4th day after chemotherapy. Conclusion: EPR oximtry measuring technique can be used to dynamically monitor the PO2 in tumor microenvironment during the chemotherapy and catch the time window of the peak value of PO2 in tumor microenvironment after chemotherapy exactly. The banlance change between oxygen consumption of mitochondria and the RBF may be one of the mechanisms for PO2 change during ADM chemotherapy.