Journal of Surgical Oncology 2(3): 203-206 (1970)

Effect of Anemia and Polycythemia on Growth of A Me1 4 in Hamsters

Henry R. Bartos, M.D., F.A.C.P., '~~ and Lloyd s. Rogers, M.D., F.A.C.S.'73

Previous studies indicated that hyperbaric oxygenation (HPO) decreased growth of transplanted A Me14 in hamsters. The present study was designed to determine if the effect of HPO might be on the level of a growth-promoting hormone whose release is sensitive to tissue oxygen concentration. No difference in tumor growth was observed when polycythemic and anemic hamsters were compared. This observation makes it unlikely that a hormonal factor is operative in the HPO effect, and lends further credence to the hypothesis that HPO is directly toxic to tumor tissue.

INTRODUCTION Previous studies in our laboratory showed that hyperbaric oxygen (HPO) exerted certain effects on the growth of A Me1 4 hamster melanoma (DeCosse and Rogers, 1966). When compared t o controls, HPO-treated animals had (1) strikingly smaller and fewer pulmonary metastatic lesions, (2) statistically significant increased survival, and (3) slightly smaller primary tumors and hepatic metastases. The mechanism by which HPO produced these effects was not elucidated, but a direct antitumor action of HPO was postulated.

Another possible explanation is that the secretion of a hormonal factor by the animal necessary for A Me1 4 growth might be inhibited by high tissue oxygen concentration. If this were true, then HPO would cause a decreased output of this factor leading t o diminished tumor growth. Polycythemic animals should also have

This study was supported by USPHS Grant No. HE-06052 from the N.I.H. Departments of Medicine and Surgery, State University of New York Upstate Medical Center, and the Veterans Administration Hospital, Syracuse, New York. Assistant Professor of Medicine, Attending Physician, Syracuse Veterans Administration Hospital. Professor of Surgery, Chief, Surgical Service, Syracuse Veterans Administration Hospital.

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less of this factor, and anemic animals should have more; thus, if such a hormonal mechanism were operative, tumor growth should be suppressed by polycythemia and facilitated by anemia.

The present study was designed to test this theory.

MATERIALS AND METHODS Twenty-four male Syrian golden hamsters weighing about 100 g each were

used in the study. Twelve animals were assigned to the ‘anemic’ group and 12 to the ‘polycythemic’ group. The animals were anesthetized with ether. Three milliliters of blood was drawn into a heparinized syringe by cardiac puncture from each animal in the ‘anemic’ group. The hematocrit was measured, the blood was pooled, and packed cells were obtained. The animals in the ‘polycythemic’ group had a cardiac puncture, 0.2 ml of blood was withdrawn for a microhematocrit, and 1.0 ml of packed cells was injected. Two minutes after initial cardiac puncture, another 0.2 ml of blood was withdrawn from each animal for microhematocrit and the cardiac needle was withdrawn.

While the animals were still under anesthesia, approximately 4 x106 viable A Me1 4 tumor cells were injected into the thigh. On the sixth day after injection all animals were killed, and tumor size, lung weight, and pulmonary histology were evaluated in each group.

RESULTS Before manipulation, the 24 animals had a mean hematocrit of 47 f2 (sD).

After manipulation, three animals assigned to the anemic group and two animals assigned to the polycythemic group died and could not be evaluated. The nine remaining animals in the anemic group had a mean hematocrit of 32, with a standard deviation of f5. The 10 remaining animals in the polycythemic group had a mean hematocrit of 53&3.

Mean tumor weight in the anemic group was 2.5 g, with a standard deviation of f1.2. Mean tumor weight in the polycythemic group was 2.8k0.7.

Lung pathology was no different in the two groups. Both showed copious metastases similar t o the control animals in the previous HPO study (DeCosse and Rogers, 1966).

DISCUSSION Although the data are confusing, hyperbaric oxygen (HPO) has been reported,

in some studies, to increase the effectiveness of radiotherapy (Churchill-Davidson et al., 1966) and chemotherapy (Lottofeldt et al., 1966; Siege1 and Morton, 1967) in the treatment of malignancies. These reports led DeCosse and Rogers (1966) in our laboratory to study the effects of HPO on the transplanted A Me1 4 tumor in ham- sters. Enhancement, by HPO, of drug treatment of this tumor was not found, but

Effect of Anemia and Polycythemia on Growth of A Me1 4 in Hamsters 205

there was a prolongation of survival, a markedly lesser degree of pulmonary metastases, and slightly smaller tumors in HPO-treated animals. The mechanism by which HPO produced this antitumor effect was not elucidated, but it was postu- lated tha t the HPO had a direct toxic effect upon the tumor cell.

It has been suggested tha t nucleic acid synthesis in bone marrow stem cells may be altered by erythropoietin (Rambach et al., 1957; Pieber-Peireta et al., 1965). Erythropoietin secretion is depressed with polycythemia, presumably secondarily t o increased tissue oxygenation (Jacobson et al., 1957). Thus, exposure t o HPO might be expected to decrease erythropoietin secretion, as would transfusionpolycythemia; on the other hand, anemia induced by bleeding might increase secretion of the hor- mone. There is a possibility tha t erythropoietin or some similarly oxygen-sensitive agent might play a role in the growth of A Me1 4 in hamsters.

The present experiment was designed t o test the possibility tha t the previously observed effect of HPO on hamster A Me1 4 (DeCosse and Rogers, 1966) was due t o suppression of such a growth-promoting hormone. If this were true, then induced polycythemia should have had an antitumor effect similar t o HPO, whereas anemia should have promoted tumor growth. The observation tha t there was no difference in tumor size or metastases between the anemic and polycythemic animals is evidence tha t HPO did not exert its effect through such a hormonal mechanism. This lends further credence t o the hypothesis t ha t HPO may be directly toxic to the tumor cell.

I n other circumstances, where rapid cell division is a factor, HPO appears t o exert a detrimental effect. One example of this is the demonstration by Wrey and Rogers (1968) in our laboratory tha t the strength of healing fractures is reduced by HPO in animals. The mechanism by which HPO exerts a deleterious effect upon rapidly dividing cells is unknown, and remains t o be elucidated.

ACKNOWLEDGMENTS The authors wish to acknowledge the technical assistance of Mrs. Dorothy

Secor and Mrs. Loraine McGuire, and the assistance of Miss Jo Ellen Taylor in typing the manuscript.

REFERENCES Churchill-Davidson, I., Foster, C. A., Wiernitz, G.. Collins, C. D., Pizey, N. C. D., Sheggs, D. B. I., and

Purser, P. R. (1966). The place of oxygen in radiotherapy. Brit. J . Radiol. 39: 321. DeCoase, J. J., and Rogers, L. S. (1966). Influence of high-pressure oxygen and chemotherapy on the

A-Me1 4 hamster melanoma. Cancer Res. 26: 287. Jacobson, L. O., Goldwasser, E., Plzak, L. F., and Fried, W. (1957). Studies on erythropoiesis Part IV.

Reticulocyte response of hypophysectomized and polycythemic rodents to erythropoietin. Proc. SOC. Exptl. Biol. Med. 94: 243.

Lottofeldt, F. I., Schwartz, S., and Kritvitt, W. (1966). Hyperbaric oxygen, whole body x-irradiation, and cyclophosphamide combination therapy in mouse leukemia L 1210. J. Natl. Cancer Inst. 36: 37.

Pieber-Peireta, M. P., Rudolph, W., Hodgsen, G., and Peireta, M. A. (1965). Effect of erythropoietin on (“C) formate incorporation into rat bone marrow RNA. Bioeh.int. Biophys. Acta 95: 360.

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Rambach, W. A., Alt, H. L., and Cooper, J. A. (1957). The mode of action and nature of a heat stable

Siegel, B. V., and Morton, J. I. (1967). Potentiation of the immunosuppressive effect of cytoxan in

Wrey, J. B., and Rogers, L. S. (1968). Effect of hyperbaric oxygenation upon fracture healing in the rat.

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