[Antiproliferative activity of difluoromethylornithine and the factors decreasing its effectiveness in malignant growth].

The inhibitory effect of difluoromethylornithine (DFMO) synthesized by the authors on the activity of the ornithine decarboxylase (ODC) and proliferation of microbial and mammalian cells in vitro was studied. The in vivo growth of ascite plasmocytoma of solid melanoma B-16 cells in mice was also effectively inhibited by DFMO. But the antiproliferative activity of DFMO in solid tumours was substantially lower. Such a decrease in the antitumour activity may be associated with polyamines released from necrotic areas of solid tumours. As the tumour cells "catch" the vitally important metabolites, their effect inside solid tumours is turned against the tumour cells themselves. The second reason of the decrease in the DFMO activity is adsorption of polyamines on the erythrocyte surface.