Aquired Radioresistance of Tumour Cells

Abstract

RADIORESISTANCE of tumours, which appears as a result of repeated irradiation, was described in 1904 by Lassueur¹. Certain characteristics were later examined: tumour ploidy^2–6; the state of the mitochondria⁷ and ribosome⁸; the content of sulphydryl groups^9,10; the capacity for anaerobic glycolysis¹¹; catalase activity¹²; and changes in the immune relationships between tumour and organism¹³. The mechanism of the enhancement of tumour radioresistance, however, remains unknown. In experiments with Ehrlich ascites tumours in mice we have obtained radioresistant strains. This was achieved by intraperitoneal reinoculation preceded by irradiation of the tumour with 300 r. in vivo for 3 consecutive days and a single dose of 1,000 r. in vitro. We made between 50 and 120 passages in these conditions of repeated irradiation. The difference in radiation response of rhythmically irradiated and initial strains of Ehrlich tumour was determined after check-up irradiation with 1,000–3,000 r.