Effects of cyclophosphamide on immunity against chemically‐induced syngeneic murine sarcomas

Abstract

The effects of cyclophosphamide (CY) on tumor immunity against syngeneic murine fibrosarcomas induced by 3‐MCA (3‐Methylcholanthrene) were studied using transplantation techniques. Five different groups of BALB/c female mice were challenged with viable cells of a 3‐MCA sarcoma (AT‐008). Mice bearing a sensitizing transplant of this tumor at the time of challenge were significantly resistant compared to non‐sensitized, untreated controls and compared to non‐sensitized mice pretreated with CY. Mice which had been sensitized by inoculation and subsequent excision of this tumor were more resistant than the tumor‐bearing mice. The greatest resistance, however, was observed in mice bearing syngeneic transplants of AT‐008 and treated with CY 6 days prior to challenge. These findings suggest that CY not only fails to suppress but may actually intensify established tumor immunity in this animal system. The results support the suggestion that tumor growth inhibition achieved with some chemotherapeutic agents may be accomplished partially through immunologic mechanisms.