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Cancer
Treatment Reviews (1984) 11, 131-155
Krestin
(PSK)
Tsukagoshi, S.,* Hashimoto, Y.,** Fujii, G.j Kobayashi, H.,T Nornoto, K.§
and Orita, K.
*
Cancer Chemotherapy Center, The Japanese Foundation for Cancer Research,
Tokyo, **Department
of Hygienic Chemistry,
Pharmaceutical Institute, Tohoku University, Sendai, Department of
Clinical
Oncology, Institute of Medical
Science, University of Tokyo, Tokyo, Laboratory of
Pathology, Cancer
Institute ' Hokkaido
University, School of Medicine, Sapporo, § Department of Immunology,
Medical
Institute of Bioregulation,
Kyushu University, Fukuoka, and The First Department of Surgery,
Okayama University, Medical
School, Okayama, Japan.
Introduction
Numerous
reports have described the antitumor effects of polysaccharides isolated
from various natural sources. Hemicellulose fractions (67, 68, 105,
106), bamboo (101), fungi (12, 31, 32, 96), bagasse (88), lichen (98),
yeast (10, 11, 89), bacterial lipopolysacchrides (58) and glucans have
been examined for antitumor activity against various experimental
tumors. These polysaccharides are considered to possess a similar mode
of antitumor action.
In
Japan some fungi belonging to Basidiomycetes
have been used as folk remedies for the treatment of malignant
neoplasms. In this review we examine experimental studies of a protein
bound polysaccharide preparation, Krestin (PSK), extracted from Coriolus versicolor which belongs to Basidiomycetes.
Characteristics
of PSK.
PSK
is obtained as follows. Cultured
mycelia of Coriolus versicolor (Fr.)
Qual. belonging to Basidiomycetes are
first extracted with hot water and then the precipitate is separated
from clear supernatant by using saturated ammonium sulfate, desalted, and
dried. PSK is a brownish powder
with a slight characteristic odor; it is sparingly soluble in methanol,
pyridine, chloroform, benzene, and hexane, but highly water soluble. The
pH of a PSK solution in water is about 7.
An
average molecular weight of PSK is 9.4 x 104 as measured by ultra
centrifuge analysis. Liquid chromatographic analysis of PSK after
hydrochloric acid hydrolysis reveals the protein portion of PSK to
consist predominantly of acidic amino acids such as aspartic acid and
glutamic acid and neutral amino acids such as valine and leucine with
basic amino acids including lysine and arginine present in small amounts
(Table 1). Determination of C-terminal and N-terminal amino acids by an
isoelectric point fractional
0305-7372/84/020131
+ 25 (C) 1984 Academic
Press Inc. (London) Limited
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