Effects of route and schedule of administration of high-molecular levan on the growth of AKR lymphoma.

The route and schedule of treatment with high-molecular levan markedly influences its inhibitory effect on the growth of transplanted AKR lymphoma. Injections of levan into the site of the primary tumor were more effective in inhibiting tumor growth and preventing tumor-associated weight loss and mortality than were i.p. injections. Local levan injections inhibited metastatic spread only in mice treated from Days 0 and 2. Levan i.p. was more effective in inhibiting metastases in animals started on treatment 7 to 13 days after tumor inoculation than in animals in which levanization was started earlier. Local injection of levan before inoculation of tumor enhanced tumor growth and shortened life-span in comparison to nonlevanized animals. In mice treated with levan for a short period only, the inhibitory effect on tumor growth slowly vanished within 2 weeks. Some animals treated for 5 to 8 months remained completely free of tumor. The results indicate that the effect of levan on tumor development is mainly topical and depends on the concentration of the polysaccharide in the site. The tumor growth period from 0 to 5 days appears to differ from the following period in the reaction to levan treatment. The nature of this difference is not clear, but possible explanations are discussed.