I HORMONAL FACTORS 847 



Hyperthyroidism may depress tumorigenesis in ovaries transplanted to the 

 spleens of castrated mice (Miller and Gardner, 1954). Although the post-castra- 

 tional adrenal-cortical adenomas appearing in thiouracil-treated mice may be 

 non-functional (neither estrogenic nor androgenic activitiy), hormone production 

 was exhibited by the cortical adenomas of radiothyroidectomized-gonadectomized 

 mice (Luckman and Kirschbaum, unpublished). 



Results relative to the effect of thyroidectomy on the growth of transplanted 

 tumors have been contradictory. The only reliable procedure for ablating the 

 mouse thyroid gland is radiothyroidectomy. A transplanted fibrosarcoma grew 

 equally well in normal and radiothyroidectomized mice (Sloviter, 1951). Total 

 thyroidectomy was reported to prolong significantly the interval between methyl- 

 cholanthrene injection and the time of development of sarcoma in rats (Woyson 

 et al., 1956). The number of athyroid rats developing induced tumors was 86%, 

 compared with 100% tumor development in intact animals. Since animals were 

 not pair-fed in this and other experiments, caloric intake has not been eliminated 

 as a factor determining the difference in response of intact and athyroid animals. 



[k) Diabetes and the growth and development of neoplasms 



Sarcoma 37 grew equally well in normal and alloxan diabetic rats (Carrie and 

 Ham, 1949). The diabetic state did not alter the susceptibility of rats to the in- 

 duction of sarcoma by benzpyrene (Dunning et al., 1949). It has been reported, 

 however, that diabetic rats (Goranson et al., 1954) and mice (Jehl et al., 1955) do 

 not support the growth of specific transplanted tumors as well as non-diabetic 

 controls. Azo dye carcinogenesis was inhibited in alloxan-diabetic rats (Salzberg 

 and Griffin, 1952). 



II. IONIZING RADIATIONS AND CANCER 



There is clinical evidence that ionizing irradiations may be carcinogenic. Lung 

 cancer in the Schneeberg miners (Hvieper, 1942), skin cancer following heavy 

 X-irradiation (Hesse, 191 1), malignant bone tumors after prolonged retention 

 of radium in osseous tissue (Martland and Humphries, 1929), tumors of the bony 

 pelvis after irradiation (Fournier, 1935), laryngeal tumors as a consequence of 

 roentgen treatment of Graves disease (Petrov, 1932) and the increased incidence 

 of leukemia among the survivors at Hiroshima (Moloney, 1955) contribute 

 to the conclusion that ionizing radiations represent a carcinogenic hazard in 

 man. 



[a) Local action of ionizing radiations 



Experimentally, local irradiation has resulted in the induction of tumors of the 

 skin and subcutaneous tissue. A high percentage of mice in-ected with ^'Y phos- 

 phate or 2^^Pu developed fibrosarcomas (Lisco et al., 1947b). Feeding of ^^Y induces 

 adenocarcinoma of the colon after a relatively long latent period (Lisco et al. , 1 947a) . 

 As little as one microgram of radium deposited in the human skeleton may be 

 carcinogenic (Brues, 1954). Bone tumors have been induced by radioactive ele- 



Literalure p. 870 



