Paramagnetic changes in cancer: DMBA-induced tumours studied in non-lyophilized and lyophilized tissues

Electron spin resonance (ESR) studies were made on frozen samples of 7,12 dimethylbenzanthracene (DMBA)-induced rat breast tumours both before and after lyophilization. The primary purpose of these studies was to determine the relationship between ESR spectra under these two conditions and thereby hopefully resolve an apparent conflict as to the experimental findings and clinical implications of these findings. In contrast to the other system (Walker 256 carcinosarcoma) which we studied by a similar method, in the DMBA-induced tumours we found a close parallel between the ESR spectra before and after lyophilization. In both cases free-radical levels were elevated about two-fold in all tumours and showed little dependence on the age of the tumour. Studies of blood and liver before the development of tumours showed no change in free radicals levels in either nonlyophilized or lyophilized samples. In animals with tumours, the level of free radicals in the liver increased approximately 17%. Manganese (2+) levels were increased in breast tumours but the changes did not closely follow those of free radicals and were much more variable in the lyophilized samples. We conclude that: (1) there seems to be no general relationship between ESR spectra of tumours before and after lyophilization; (2) there appears to be no general pattern of ESR changes in lyophilized samples of tumours.