Author/Editor     Šentjurc, Marjeta; Čemažar, Maja; Serša, Gregor
Title     EPR oximetry of tumors in vivo in cancer therapy
Type     članek
Source     Spectrochim acta, Part A: Mol Biomol Spectrosc
Vol. and No.     Letnik 60
Publication year     2004
Volume     str. 1379-85
Language     eng
Abstract     The partial oxygen pressure (pO2) in tumors is considered to be one of important factors that affect the response of tumors to different treatment. Therefore, we anticipate that the information about the variation of oxygen concentration in tumors can be used as a guide for, individualizing radiotherapy, chemotherapy, and espccially the combined therapies. There is thus a need to obtain quantitative data on the effects of different therapies on tumor oxygenation under in vivo conditions. One of the methods, which enable these measurements is EPR oximetry. In this work basic principles of the method will be described as well as some examples of tumor oxygenation changes after application of chemotherapeutic drugs (vinblastine, cisplatin, bleomycin) or electric pulses in cornbination with cisplatin or bleomycin to fibrosarcoma SA-1 tumors in mice. A paramagnetic probe, a char of Bubinga tree, was implanted into the tumor (center and periphery) and in the muscle or subcutis. EPR spectra line-width, which is proportional to oxygen concentration, was measured with time after the treatments. Tumor oxygenation was reduced for 58% of pretreatment value 1 h after intraperitoneal injection of 2.5 mg kg-1 VLB and returned to pretreatment Ievel within 24 h. Reduction in oxygcnation of muscle and subcutis was much smaller and returned to pretreatment value faster as in tumors. With cisplatin: (4 mg kg-1) and bleomicyn (1 mg kg-1) the reduction was Iess than 15%, but increases in combined therapy to 70%. Similar reduction was obscrved also with electric pulses alone (eight pulses, 1300 V cm-1, 100 micros, 1 Hz) with fast recovery of 8 h. After electrochemotherapy the recovery was slower and occurs only after 48 h. This study demonstrates that EPR oximetry is a sensitive method for monitoring changes in tissue oxygenation after different treatments which may have implications in controlling side effects of therapy and in the planning of combined treatments.
Descriptors     FIBROSARCOMA
ELECTROPORATION
DRUG DELIVERY SYSTEMS
OXIMETRY
VINBLASTINE
CISPLATIN
BLEOMYCIN
ELECTRON SPIN RESONANCE SPECTROSCOPY
MICE, INBRED A