The Effect of Variations in Oxygen Pressure upon Tumor Transplants (1942)

(From the Clayton Foundation and the University o/ Texas, Biochemical Institute, Austin, Texas) (Received for publication June 29, I942) Since Warburg's classical experiments showing that tumors differ from other tissues in their requirements of and reactions toward oxygen (16), there have been a number of attempts to influence the development of tumors in animals changing the oxygen pressure in the inspired air. Some measure of success has been reported investigators who employed increased oxygen pressures as well as some who used decreased oxygen pres- sures, but nothing of therapeutic value has thus far resulted. Warburg did most of his work with tumor slices in vitro (I6), but he also showed that tumor cells could be destroyed in the host placing the animals in an atmosphere containing only 5 per cent of oxygen (i7). The bulk of the implanted tumors was killed in 4o hours, but the cells at the periphery remained alive. Campbell and Cramer in 1928 obtained similar results (6) upon exposing mice bearing implanted tumors to an oxygen pressure of about io per cent for 2 weeks. A quotation giving some of their conclusions is of interest: Exposure to low oxygen tensions, however, is a general con- dition which damages malignant tissue more sevcrely than normal tissue. It has, moreover, this advantage, that since its action extends over the whole organism it will produce its effect on malignant tissue in its metastatic deposits. Unfortu- nately, it does not damage it so completely as to be of thera- peutic value itself, for since a fraction of the malignant cells survive, they resume their growth when normal conditions are reestablished. Since then there has been very little work on this phase of the problem. Sundstroem and Giragossintz (14) placed rats bearing the Jensen sarcoma or the Flexner-lobling carcinoma under reduced atmospheric pressures (in the neighborhood of one-half atmosphere) for several weeks and reported 24 to 83 per cent definite cures. Some work has also been done on the production of anoxia in other ways. In i932 Campbell (3) reported that the rate of growth of mouse carcinoma 63 was retarded exposing the animals to small concentrations of carbon monoxide. No such effect was observed with the Rous fowl sarcoma, but he later reported (4) that this treatment retarded the growth of tar- induced skin cancers, although it did not prevent their de- velopment. Maxwell and Bischoff (13) confirmed this effect of carbon monoxide with tumor-bearing rats and mice, and re- ported that hydrogen cyanide had a similar action. Meanwhile the effects of high oxygen pressure upon tumor growth and development had also been under investigation. Fischer and Andersen (8) found that Rous fowl sarcoma cells were more readily destroyed high pressures of oxygen than were corresponding nonmalignant tissues, and later (9, IO) they succeeded in producing a number of regressions maintaining tumor-bearing mice under 1.6 to 2.o atmospheres of pure oxygen for I8 to 24 hours. This treatment was effective only when the transplants were very small. Campbell and Cramer (6) studied the effect of maintaining rats and mice bearing transplanted tumors in an atmosphere containing 60 per cent of oxygen continuously for 2 weeks, but found no effect on the rate of growth of the tumors. In I931 Marsh (I2) reported the results of experiments wherein he kept mice under 3 ~ to 4 ~ pounds' pressure of air for most of their lives and observed a decrease in the incidence of spontaneous mammary tumors. However, he did not attribute much significance to this finding because of wide variations in his experimental conditions. l)e Almeida (r) extended the work of Fischer and Andersen keeping rats bearing the Roffo spindle cell sarcoma under from , to 8 atmospheres of pure oxygen for lengths of time close to the toxic limit (24 hours to 2o minutes). These treat- ments were given intermittently, and under the best conditions~ 6 atmospheres of oxygen by hourly treatments-- 7 per cent of regressions was obtained. However, he found further that the resistance of the rats to the toxic action of the oxygen could be increased allowing them to fast for 2 to 3 day's, and with this modification recorded that the cures rose to 23 per cent. Campbell employed similar conditions with mouse and rat tumors (not including the Roffo rat sarcoma, however) but was unable to obtain any regressions (5)- In view of the foregoing results, which appear promising although inconclusive, we decided to in- vestigate the effects of high and low oxygen pressure upon transplants of a mammary gland adenocarcinoma in dba mice, a tumor which we have found to have uniform growth characteristics and to produce almost Ioo per cent mortality. In different experiments we therefore employed high as well as low atmospheric pressure as a means of changing the oxygen tension of the tissues. However, it has been shown that large changes in external oxygen pressure produce only small changes in the oxygen tension of the tissues. For example, Campbell (2) has reported that the oxygen tension under the skin of rabbits is raised from 14 to only 26 ram. (which appears to be a limiting value) raising the external oxygen pressure from 53 to 42o ram. We therefore included an experiment wherein bubbles of pure oxygen were injected under the skin of mice in vicinity tumor im- plants as a means of exposing the tumors directly to much higher oxygen tensions than was possible increasing the inspired oxygen pressure. In connection with the use of low oxygen pressure we were also interested in using the most strenuous conditions indicated previous work. In the case of the partial tumor destruction obtained Warburg (17) , he explained his results as due to a suffocation 828