Antitumor effects on mouse colorectal Colon-26 tumors in mice induced by normal tissue treatment using streamer discharge*

We previously reported antitumor abscopal effects in mice induced by tumor treatment using streamer discharge (K. Mizuno et al, J. Phys. D, 50, 12LT01, 2017). When one of the tumors in mice with two mouse melanoma B16F10 tumors was irradiated with streamer discharge, antitumor effects was observed in the other tumor, which was not irradiated with discharge, as well as in the irradiated tumor. This remote antitumor effect is called abscopal effect, which is well-known phenomena in radiotherapy. In the current study, the abscopal effect induced by normal tissue irradiation, not by tumor irradiation, is reported. When the discharge was irradiated on the upper left back of mice, which have mouse colorectal Colon-26 tumors in the right flank, the tumor growth was delayed. The distance between the tumor and irradiation point was 2 to 3 cm. The abscopal effect induced by normal tissue treatment was not observed in immunodeficient mice. This suggests that the abscopal effect is related to some adaptive immune responses.