THE EFFECT OF RADIATION ON FROZEN 



TUMOUR CELLS 



Ilse Lasnitzki* 

 Strangeways Research Laboratory, Cambridge 



It has been shown by several observers that the response to radiation can 

 be influenced by the metaboHc activity of irradiated biological material. 

 Glucksmann and Spear ^ demonstrated that in tadpoles the radiation effect 

 was delayed if the animals were chilled during and after exposure. Gold- 

 FEDER-, comparing the radio sensitivity of histologically similar mouse tum- 

 ours found the radiation effect more marked in those showing a lower 

 metabolic rate. A similar result was obtained by me^ with the S3 7 tumour 

 exposed as ascites and subcutaneous form. For the ascites form, which 

 according to Warburg and Hiepler* functions at very low energy levels, 

 the MLD found was one-fifth of that for the solid sarcomas. 



In recent years Craigie^ and other workers have shown that certain 

 tumours preserve their viability if frozen and kept at temperatures of dry 

 ice and liquid air. This ability should make them a convenient material 

 to study the effect of radiation in the frozen state at which metabolic activity 

 is at a standstill, and in the present experiments the effects of radiation on 

 tumours in the fresh and frozen state were compared. 



EXPERIMENTAL 



The material used was the Ehrlich ascites tumour. This tumour is frozen and 

 stored on dry ice as a routine in our laboratory as an alternative to serial transplan- 

 tations and samples stored, for instance, for several months proved to be viable on 

 re-inoculation. The tumour cell suspensions were frozen at — 79° and kept at this 

 temperature for 7 days prior to irradiation. Exposure took place in vitro. The 

 dose was 1,500 r units at 75r/min. Two experiments were made. In the first 

 one the frozen cell suspension was exposed on the laboratory bench and gamma rays 

 were used ; in the second one it was irradiated on dry ice and X-rays were used. The 

 frozen cells were thawed quickly immediately after exposure and injected subcu- 

 taneously into C3H mice. For comparison of the radiation effect fresh cells obtained 

 from the same tumour sample were exposed in an identical manner and inoculated 

 subcutaneously into the same strain of mice. Each set had its own unirradiated 

 fresh and frozen control grafts. Each inoculum contained approximately 15 X 10® 

 tumour cells. The criterion of radiation effect was the number and size of .sub- 

 cutaneous tumours obtained. 



RESULTS 



Figure I gives the percentage take obtained after inoculation of frozen and 

 fresh unirradiated grafts. One week following inoculation it is 80 per cent 

 for grafts derived from fresh and 90 per cent for grafts from frozen cells, an 



* Sir Halley Stewart Fellow. 



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