Control of Oxygen Utilization In Vitro and In Vivo: Implications for Radiotherapy of Tumors

Abstract

Several studies have shown that as a tumor increases in size, its QO₂ decreases^1,2. Measurements on tumor homogenates in vitro and in vivo perfusion studies, indicate large variations in oxidative capacity among various types of tumors³. However, we have previously found that human tumor cells in log-phase culture as well as log-phase cultures of mammalian cells have similar oxygen consumption rates⁴. Some cultured lines show a decrease in oxidative capacity in plateau phase growth^5,6. The differences between QO₂ values obtained for in vitro versus in vivo cells as well as the differences between log and plateau phase growth suggest that metabolic controls or cellular adaptations are operative in vivo. Similar controls may or may not operate or exist in vivo. Tberefore we have initiated a study of the possible factors that might influence cellular oxygen consumption for a number of murine tumors including the mouse mammary carcinoma (MCaIV), a fibrosarcoma (FSaII), a squamous cell carcinoma (SCCaVII), the Ehrlich ascites tumor and the rat brain carcinoma (9L). We have compared the tumor rates with cultured FSall as well as HEp-2, the A549, a human lung carcinoma and the V79 Chinese hamster lung cell.