The Action of Radiation on Living Cells

Abstract

It is obviously true that a better knowledge and understanding of the laws of growth of all types of cells will be necessary before many of the fundamental biologic problems in the fields of cancer research in general and radiation therapy in particular can be solved. The Committee on Growth of the K ational Research Council seeks to obtain information on these and related subjects. At one time, study of tissue cultures seemed to offer distinct possibilities along these lines, but the difficulty of growing cultures of epithelial and lymphatic neoplasms or cellular tissues with scanty stroma presents definite limitations. Limitations also exist in the amount of information which can be obtained from studying histologic sections because of their static nature, and it now appears that progress may be made from the develop men t of radiochemistry of organic substances or the use of radioactive tracer technics including autoradiography. Some of the early observations on the action of radiation on cells were made by British workers (1). They considered increased knowledge of the reactions exhibited by normal healthy cells necessary before the real nature of the processes initiated by radiation in tumors could be determined. A successful two-day conference arranged by the British Institute of Radiology was held in London in the spring of 1946, when the general subject for discussion was “Certain Aspects of the Action of Radiation Upon Living Cells.” Since the membership of the Institute includes those concerned with the production or application of ionizing radiation in medicine, biology, and physics, the officers emphasized both biologic and physical aspects in the papers and discussions. Among the topics included were “The Distribution of Ions Resulting from the Irradiation of Living Cells” and “The Action of Radiation on Viruses, Dilute Aqueous Solutions, Chromosomes, and Germ Cells, with Special Reference to Man.” From the standpoint of clinical radiotherapy, one of the most important papers was by Dr. P. C. Koller (3), who pointed out that the radiation effects on tumor cells induced by direct ionization were temporary and reversible, or permanent and irreversible. The most important temporary effect was suppression of mitosis. Data obtained from two squamous and two basal-cell carcinomas showed that the number of dividing cells was considerably reduced after 200 r, and that single doses of 400, 500, or 600 r suppressed mitosis for several days. Koller and Smithers (4) showed that, by taking into consideration recent cytologic investigations, a treatment method could be devised for individual tumors in which the total dose did not exceed 3,200 to 3,600 r. They demonstrated the importance of the mitosis suppressing effect of irradiation on the treatment of tumors and the consequences of its dependence on the intensity or rate of flux.