THE IN-VITRO RADIOSENSITIZATION OF HUMAN GLIOBLASTOMA WITH PENTOXIFYLLINE

There is evidence that pentoxifylline may be both a radioprotector of normal tissue and a radiosensitizer of tumor cells. This article revie ws this evidence and then describes our own laboratory study to determ ine whether pentoxifylline is a radiosensitizer of human glioblastoma cells in vitro. Human glioblastoma multiforme cells (SNB19 cell line) were irradiated in vitro with and without pentoxifylline. Regression o f the log ratios (quotient of surviving colonies) revealed greater tum or cell kill in the PTX group, and the difference increased as the rad iation dose increased (p < 0.01 at the 750 and 1000 cGY doses). Before the hypothesis that PTX is a radiosensitizer of hypoxic tumor cells c an be confirmed or denied, it must be determined if the agent also has a separate mechanism of tumoricidal activity. Whereas in vivo models allow the well-documented rheologic, immunologic and oxygen-related ef fects of PTX to be active simultaneously, the in vitro model described herein excludes the effects of such systemic actions and focuses on m echanisms at the cellular or subcellular level. These data suggest the re exists such a mechanism of tumoricidal activity of PTX that has not been previously identified.