EXPERIMENTAL ANTICANCER STUDIES

摘要

References(13) Cited-By(1) It was demonstrated by Koshimura et al. in 1955 that Ehrlich ascites carcinoma cells, in phosphate-buffered Ringer's solution, kept for a short time at 37°C in contact with well washed living virulent hemolytic streptococci (Sv) no longer possessed of the power of invading mice (1). In their experiment, the mice were treated with penicillin, so that the animal survived the infection. Soon after, it was also observed that a significant quantity of streptolysin-S was produced in the medium of this kind of experiment (2)—an observation suggesting occurrence of interaction between living hemolytic streptococcus and ribonucleic acid contained in carcinoma cells (3). Any way, this is the beginning of the anticancer experiments now being developed in our laboratories (3). The principal results obtained up to the present are as follows : 1) In contrast with living hemolytic streptococci, heat-killed cocci were ineffective to suppress the invasion power of the tumor cells (1). 2) The anticancer activity appears to be specific for β-hemolytic streptococci, and seems to be not shared by other gram-positive and gram-negative bacteria (6). 3) Supernatant of culture fluid of hemolytic streptococcus, purified streptolysin-S sample, desoxyribonuclease, varidase [DNase+streptokinase (or fibrinolysin)], pancreatic ribonuclease, hyaluronidase, all were also tested to be entirely ineffective in this respect (3, 7). 4) A nearly avirulent-mutant strain of hemolytic streptococci was as effective as its virulent-mother strain (Sv) in depriving the invasion power of carcinoma cells to mice (8). 5) Intratumoral injection of living hemolytic streptococci caused destruction of solid tumor of Ehrlich carcinoma cells in mice (9). 6) Yoshida sarcoma, Sarcoma 180 and leukemia SN 36 cells were also affected by hemolytic streptococci (10). 7) Cell-free extract, prepared under strictly controlled conditions from hemolytic streptococci, was effective in causing the loss of invasion power of Ehrlich carcinoma cell (as well as in synthetizing streptolysin-S in the simple medium containing yeast ribonucleate) (11). Moreover, it should here be added following two experimental results: a) Jordan and his associates have recently made an observation that infection with group A hemolytic streptococci was effective in causing massive degeneration and necrosis of leukemic tumor in mice (12). b) Christensen and Kjems have reported that both living hemolytic streptococci and the phage-lysate of the cocci were inhibitory against Brown-Pearce carcinoma in rabbits (13). The purpose of the present work was to obtain some lights on the question whether or not the anticancer effect of hemolytic streptococci could be expected in immunized animals to the cocci.