Co-Carcinogenesis in the Hamster Cheek Pouch

¹ Oral Medicine and Surgery Branch, National Institute of Dental Research, National Institutes of Health, United States Public Health Service, Bethesda, Maryland

Single x-ray doses of 500 R, 1,000 R, or 2,000 R do not produce a co-carcinogenic effect in young hamsters when used in conjunction with the painting of a 0.5 or 0.05 per cent concentration of DMBA on the cheek pouch.

Tumors appeared in cheek pouches painted with 0.5 per cent DMBA in 7.5 to 12 weeks. Papillomas occurred slightly later when radiation was used in combination with 0.5 per cent DMBA painting, and tumor inducement was 100 per cent in both groups in 22 weeks. The 2,000 R plus 0.5 per cent DMBA combination was lethal for the most hamsters (100 per cent mortality in 13 weeks). The oral radiation death syndrome was observed in some of the hamsters given 2,000 R or 1,000 R alone, also.

Splenomegaly and forestomach polyp formation were the two most interesting secondary findings in the tumor-bearing hamsters. The salivary glands proved to be quite resistant to any permanent radiation-induced change.