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.