Effects of irradiation on cancer toxin in tumor-bearing hosts.

Irradiation effects on cancer toxin, "toxohormone", in tumor-bearing hosts were investigated. Crude toxohormone fractions were prepared from preoperatively co&0-irradiated human gastric cancer by the method of Yunoki and Griffin. 1) It was demonstrated tha t Co&0-irradiation reduced the liver catalase depressing action of the crude toxohormone fractions, but the yield of the fractions was less markedly affected. 2) Amberlite XE-64 column chromatography of the fractions revealed the decreased amount of the TH2 fraction which was reported to possess the most potent catalase depressing action. 3) Histological observations of the Co60-irradiated cancer were: a) focal necrosis and/or fibrosis of the tissue ; b) degenerative changes of cancer cells, which varied in severity. Irradiation effects on cancer toxin were then investigated in connection with the tumor growth, using mice bearing a diploid Ehrlich ascites tumor. 1) In tumor-bearing mice, a decrease in liver catalase activity was observed 10 hours after irradiation with 200 or 500 r of X-rays. This decrease was ascribed to an enhanced release of the cancer toxin from the irradiated tumor cells. 2) After 500 r, the arrest of cell di vision occurred, whereas the average cell volume continued to increase. This increase in volume might be due to an increase in new cell substance. On the other hand, the estimations of liver catalase activity demonstrated an increase in activity 48 hours after irradiation. 3) This later increase in liver catalase activity was a lso observed frequently after exposure to 200 r . Such irradiation effect was, however, diminished by the concomitant administration of a radioprotective agent, cysteine. On the other hand, no influence of cysteine was observed with regard to the early decrease in liver catalase activity. From these findings, the later increase in liver catalase activity was most likely interpreted to be due to the lowered amount of the cancer toxin after irradiation, which was resulted from a decreased synthesis de novo of the tox in. In other words, there was a possible relation of the radiosensitive enzymes with the synthesis of the cancer toxin by t he tumor cells. ~J{ j!l Hl3 Received for publication, August 27, 1965.