HYPERTHERMIA-INDUCED ANTITUMOR-ACTIVITY IN HUMAN GASTRIC-CANCER CELLSSERIALLY TRANSPLANTED INTO NUDE-MICE

Hyperthermia-induced antitumor activity was assessed histopathological ly and findings related to transplantation of human gastric cancer int o nude mice were examined. Fragments of human gastric cancer were incu bated at 37 degrees C to 47 degrees C for various durations of time, t hen were evaluated either histologically or with regard to delay in tu mor growth and the rates of transplantation into nude mice. Fragments exposed to 39 degrees C for 30 min to 120 min and 41 degrees C for 30 min did not differ from findings in the controls concerning tumor grow th and transplantability. In the case of 41 degrees C for 60 min or mo re, the rates of transplantation decreased significantly and there was a delay in tumor growth. At 43 degrees C for 120 min, 45 degrees C fo r 30 and 60 min, and 47 degrees C for 15 to 60 min, transplantability was nil. In the groups with a delay in tumor growth, there were irreve rsible changes in nucleic and cytoplasmic components, and in 6 groups with no evidence of transplantability, complete destruction of the gla ndular structure, pyknosis and karyorrhexis as well as disappearance o f the cytoplasm occurred in almost all cases. Thus, the thermal dose o f 43 degrees C for 120 min seems to be the minimally effective one for hyperthermia-induced tumoricidal activity.