Comparative studies on antitumor activity of Klebsiella O3 lipopolysaccharide and its polysaccharide fraction in mice.

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.