Studies on X-ray Effects. Iv. Direct Action of X-rays on Transplantable Cancers

I t has been shown in this laboratory that x-rays administered in doses sufficient to destroy a large proportion of the lymphoid tissue reduce the resistance of the animal to transplanted cancer. 1 Furthermore, both potential and established induced immunity can be destroyed by a similar process3 I t has also been shown that small doses of x-rays sufficient to stimulate the lymphocytes increase the resistance to cancer. 3 These observations bring up a number of interesting points with regard to x-rays as a therapeutic agent in the treatment of cancer. The literature on this subject is so extensive and contradictory that no at tempt will be made to review the previous work. The question of immediate interest to us in this investigation is whether or not x-rays, even in a dose above that possible for therapeutic purposes, will kill the cancer cell. I t is necessary in the light of the experiments mentioned above to rule out the action of this agent on the animal itself. To determine the cumulative, as well as the immediate effect of the direct action of powerful doses of x-rays upon tumor cells, we undertook to grow a Bashford mouse tumor (Adenocarcinoma No. 63) in successive generations of white mice, subjecting the tumor to like doses of x-rays after excision and before inoculation at each transplantation. An actively growing tumor which had been propagated