Current Status of Knowledge and Critical Issues in Tumor Oxygenation

In 1972 we started the systematic investigation of oxygenation status in (a) experimental tumor systems in rats and mice [e.g., 1–6], (b) in human tumors xenotransplanted into immune-deficient rnu/rnu-rats [e.g., 7–9], (c) in tumors derived from spontaneously tumorigenic or ras-transformed cell lines [10], and (d) in human tumors in situ [e.g., 11–15] under various pathophysiological conditions using polarographic O2 needle electrodes. In the earlier studies a cryospectrophotometric ex vivomicrotechnique was also used that allowed the measurement of HbO2 saturation in individual red blood cells in tumor microvessels [e.g., 16, 17]. Besides polarographic and cryospectrophotometric microtechniques, mathematical evaluations of the pO2 distribution in tumor tissues have additionally been used to gain an insight into the oxygenation of microareas in tumor tissues [e.g., 18–21].