In one experiment, adult mice inoculated intraperitoneally with Ehrlich ascites carcinoma cells and then exposed to sublethal X irradiation developed significantly fewer "endogenous" spleen colonies than X-irradiated controls not inoculated with tumor cells. In another experiment, results were similar when bone marrow cells from tumor-bearing mice were injected intravenously into lefhally X-irradiated mice to produce “exogenous" spleen colonies. In both experiments, the inoculum of Ehrlich ascites carcinoma cells necessary to reduce significantly the frequency of hematopoietic stem cells was found to be 8.5 X 105cells—the number of tumor cells that inhibits the immune reactivity of host mice. These findings are consistent with our working hypothesis that the immunologic hypore- activity of tumor-bearing animals is mediated through a functional defect of primitive bone marrow cells. Such a mechanism of action, similar to that recently proposed for Friend leukemia virus and for the chemical carcinogen 7, 12-dimethylbenz[a]anthracene, suggests a common pathway for the immunosuppression caused by malignant tumors.—J Nat Cancer Inst 47: 555-560, 1971.
ASJC Scopus subject areas
- Cancer Research