Mouse strain difference in the expression of antitumor activity of PS-K.

Effect of PS-K on tumor growth and antibody production was studied in inbred C57BL/6, SL, C3H/He, and AKR mice, and in colony-bred ICR mice. (1) PS-K exhibited antitumor activity on sarcoma-180 in ICR mice, but not in AKR mice. Growth of sarcoma-180 was suppressed to the intermediate extent in other strains. (2) In ICR strain, antibody production against trinitrophenyl was depressed in mice bearing sarcoma-180 and restored by PS-K. In AKR mice, on the other hand, antibody production was not depressed in tumor-bearing state and was not augmented by PS-K. Other strains showed intermediate degrees of suppression of antibody-producing capacity by sarcoma-180 and its restoration by PS-K.CR strain, the growth of Ehrlich tumor as the challenge tumor was enhanced in mice bearing sarcoma-180 as compared to that in controls. After the treatment with PS-K in this strain, however, not only the growth of sarcoma-180 but also of Ehrlich tumor was inhibited completely. On the other hand, the growth of Ehrlich tumor in AKR strain was neither enhanced in mice bearing sarcoma-180 nor inhibited by PS-K.