The antitumor activity of the
polysaccharide fraction (OPS) obtained by the
acid hydrolysis of
Klebsiella O3 lipopolysaccharide (
KO3 LPS) isolated from the culture supernatant of the decapsulated mutant strain LEN-1 (03: K1-) against both allogeneic
tumor and syngeneic
tumor systems in mice was compared with that of
KO3 LPS. OPS prolonged the life span of MM2-bearing C3H/He mice by intraperitoneal (i.p.) pre- and post-treatment at the doses of 100 and 1000 mg/kg. However, large amounts of OPS were needed to show the antitumor activity as compared with
KO3 LPS. OPS showed no growth inhibitory activity against Meth-A
sarcoma in BALB/c mice by i.p., intravenous (i.v.) or intratumoral (i.t.) administration. When 1000 mg/kg of OPS was i.p. administered once a day for 10 days, OPS significantly inhibited the
tumor growth of Sarcoma-180 solid type
tumor. On the other hand,
KO3 LPS significantly suppressed the growth of Meth-A
tumor by i.t. administration at the doses of 0.3 and 1.0 mg/kg and showed complete regression in 8 and 9 out of 10 mice, respectively. In MM2
tumor,
KO3 LPS also showed complete regression in all mice post-treated by i.p. administration at the dose of 1.0 mg/kg. These results suggest that OPS has antitumor activity on the
tumors used in this study, but the activity was less than that of
KO3 LPS.