Journal of Neuro-Oncology 36: 113–121, 1998.  1998 Kluwer A cademic Publishers. Printed in the Netherlands. L aboratory Investigation Effects of D FMO on glioma cell proliferation, migration and invasion in vitro A-Jorge A. Terzis, 1 Paal-Henning Pedersen, 2 Burt G. Feuerstein, 3 Hans Arnold, 1 Rolf Bjerkvig, 2 and Dennis F. Deen 3 1 Department of Neurosurgery, L uebeck, Germany; 2 Institute of A natomy and Cell Biology, Bergen, Norway; 3 Brain Tumor Research Center, San Francisco, USA Key words: glioma, polyamines, invasiveness, DFMO, three dimensional culture Summary The polyamine inhibitor DL-α-difluoromethylornithine (DFMO) is a specific irreversible inhibitor of ornith- ine decarboxylase which is a rate-limiting enzyme in the polyamine bio-synthesis pathway. The present study describes the effects of DFMO on glioma cell proliferation, migration and invasion using multicellular sphe- roids from three glioma cell lines (GaMg, U-251Mg and U-87 Mg). 10 mM DFMO reduced cell migration in the three cell lines by about 30–50%. 1mM putrescine, added together with DFMO inhibited the DFMO effect. A stronger effect was observed in the growth assay where 10 mM DFMO reduced the spheroid growth, for all cell lines, by 90% . This effect was also reversed by adding 1 mM of putrescine. In vitro tumor cell invasion experiments indicated after 3 days of confrontation, an extensive invasion also after 10 mM DFMO treatment. The brain aggregate volumes were reduced to about the same extent as in the absence of drug, suggesting essentially no effects of DFMO on the invasive process. It is concluded that the tumor spheroids retained their ability to invade normal brain tissue even after DFMO exposure. However, DFMO inhibited spheroid growth and cell migration which supports the notion that cell growth, migration and invasion are biological properties that are not necessarily related to each other. Introduction Cerebral tumors are responsible for approximately 2% of all cancer deaths and high grade glioma is the most common cerebral tumor in adults. The glio- mas invade the brain extensively and there is no sat- isfactory treatment. The best available treatment, using surgery, radiation therapy and systematic che- motherapy, results in a median survival of  1 year [1–3]. Most failures of treatment occur because of local recurrence of the tumor. During the past dec- ade, it has been suggested that α-Difluoromethylor- nithine (DFMO), which is an ornithine decarboxy- lase (ODC) inhibitor, may be used in the treatment of gliomas either alone or in combination with other therapy regimens [4, 5]. It is well known that the aliphatic polyamines pu- trescine, spermidine and spermine are widely dis- tributed in eukaryotic cells [6], and changes in their concentrations have been associated with a number of important cellular activities [7, 8]. For instance, the polyamine biosynthetic enzymes and the con- centrations of the polyamines increase precipitous- ly when growth and differentiation is induced. It is also well known that growth stimulation of quies- cent cells and tissues invariably results in an in- creased rate of polyamine synthesis [9, 10]. In addi- tion, a large body of circumstantial evidence sug-