Heavy water delays growth of human carcinoma in nude mice.

Deuterium-enriched water has an antiproliferative effect on transplantable mouse tumors without toxic side effects. Since the response to treatment of human carcinomas growing in nude mice is deemed to be a good indicator of the potential clinical behavior of these tumors, we studied the influence of this stable isotope of hydrogen on the growth of xenotransplanted human carcinomas of various histologic types, grades, and primary sites. Seven-week-old Balb/c-nu/nu mice were inoculated subcutaneously, either with oropharyngeal squamous cell carcinomas or with carcinomas of the large intestine. After tumor inoculation, the mice were given drinking water containing 30 atom% D2O. Heavy water effectively retarded the growth of the human carcinomas. At the end of the experiment, the weight of the tumors was reduced to values ranging from 22% to 65% of the control values. The reproducible antiproliferative effect was more conspicuous in poorly differentiated carcinomas than in moderately well-differentiated variants. Since animals in both groups, kept under identical conditions, drank the same amount of water and had similar body weights, the difference in tumor growth can be attributed to the moderate deuteration of the hosts.