Dependence on chain length of antitumor activity of (1 leads to 3)-beta-D-glucan from Alcaligenes faecalis var. myxogenes, IFO 13140, and its acid-degraded products.

The well-defined (1 leads to 3)-beta-D-glucan with (DPn) 540, produced by cultivation of Alcaligenes faecalis var. Myxogenes (IFO 13140), a mutant of a soil bacterium, had marked inhibitory activity against the s.c.-implanted Sarcoma 180 at 5 to 50 mg/kg for 10 days. It also exhibited very high activity in doses of 60 and 100 mg/kg i.p. by a single injection at 7 days after the initial s.c. transplantation of Sarcoma 180. The inhibition ratios observed with Ehrlich carcinoma, NTF (Nakahara-Tokuzen-Fukuoka) reticulum cell sarcoma, and CCM adenocarcinoma were somewhat less but were still significant. On the other hand the treatment failed to inhibit the growth of ascites Sarcoma 180 or to induce prolongation of life span. The mechanism of action of this glucan was considered to be host mediated because of a lack of effect in vitro and also because of the effectiveness of pretreatment of animals by injection before transplantation of a tumor. The results from the bioassay study of the low-molecular-weight (1 leads to 3)-beta-D-glucans prepared from the glucan with number-average degrees of polymerization (DPn) 540 by hydrolysis with formic acid or sulfuric acid showed that the glucans with DPn greater than 50 inhibited the growth of Sarcoma 180 implanted s.c. in mice, whereas the result of the schedule-dependent effect was obtained in the pretreatment of animals by the glucan with DPn 50. By i.v. administration, even the glucan with DPn 16 showed a strong antitumor effect comparable to that of the glucan with DPn 540.