Immunochemotherapy of transplanted KMT-17 tumor in WKA rats by combination of cyclophosphamide and immunostimulatory protein-bound polysaccharide isolated from basidiomycetes.

Protein-bound polysaccharide Kureha (PS-K) isolated from Basidiomycetes was used in combination with cyclophosphamide (CY) for the treatment of a 3-methylcholanthrene- induced KMT-17 fibrosarcoma in WKA/Mk rats. A single administration of PS-K exhibited no inhibitory effect on the growth of s.c.-inoculated KMT-17 tumor at any timing and dose. However, PS-K exhibited a marked antitumor effect when it was combined with CY. The effect of PS-K dependend on the combination timing of PS-K and CY; a marked antitumor effect was observed when PS-K was administered before CY but not if it was given after CY or before tumor inoculation. When PS-K was administered on Day 1 followed by CY on Day 3, the highest survival rate of 78.5% (11 of 14) was obtained. Delayed hypersensitivity response of rats to KMT-17 was investigat ed by radioisotopic footpad assay. On Day 12, the hypersensitivity response in rats treated with PS-K on Day 1 and CY on Day 3 was significantly higher than that in nontreated rats, indicating an enhanced specific immunity to KMT-17 possibly resulting in a marked antitumor effect.