Long-term control of high-grade brain tumors is rarely achieved with curren
t therapeutic regimens. The major goal of this study was to determine wheth
er polysaccharopeptide (PSP), a crude polysaccharide peptide extract derive
d from Coriolus versicolor, a fungus, could enhance the effects of radiatio
n against glioma cells in culture and in xenografted tumors in vivo. PSP si
gnificantly augmented radiation-induced damage to C6 rat glioma cells in vi
tro. Nude mice injected subcutaneously with the C6 cells were treated with
PSP (injected intraperitoneally at 2 mg/injection) and radiation (2 Gy/frac
tion, 8 Gy in total) using three different time-dose protocols. Tumor volum
es were consistently smaller in all treated groups compared to the non-trea
ted tumor-bearing controls except in one group which received PSP prior to
tumor implantation. The administration of radiation alone resulted in the s
lowest tumor progression, whereas PSP alone had no effect. Furthermore, PSP
in combination with radiation treatment did not increase radiation efficac
y. Natural killer cell, lymphocyte and granulocyte counts in blood and sple
en were significantly higher in PSP-treated animals, demonstrating that PSP
has protective effects on immunological function. Collectively, these resu
lts warrant further investigation to determine if PSP can be effectively ut
ilized to upregulate immune responsiveness in case of neoplasia and other d
iseases in which immunosuppression is a prominent feature. Copyright (C) 20
01 S. Karger AG, Basel.