Failure to relate the anti-tumour action of cyclophosphamide with the immunogenicity of two murine fibrosarcomas.
A single intraperitoneal injection of cyclophosphamide (CY) had a stronger anti-tumour effect upon two syngeneic mouse fibrosarcomas when given within a few days of tumour implantation than when given 7-20 days after. CY was more active against the fast-growing, relatively non-immunogenic CBA fibrosarcoma, FS13, inducing a higher proportion and permanent regressions, than the slower-growing, highly immunogenic C57BL fibrosarcoma, FS6, at all comparable stages of tumour growth. Whole-body irradiation, which suppressed concomitant immunity in FS6-tumour-bearing mice, had no effect on the anti-tumour action of CY. A study of the cellular composition of the tumour masses over a 4-day period immediately after CY injection showed that there was a decrease in total cell yields, involving mainly a decrease in neoplastic cells, although normal cells, Fc-receptor-positive and -negative, were also affected to a lesser degree. The overall findings indicated a lack of correlation between the anti-tumour effects of CY and tumour immunogenicity. Moreover, it was apparent that the anti-tumour action of CY was mediated by a direct effect of its metabolites on neoplastic cells rather than by host anti-tumour effector mechanisms.
D000818:Animals; D003520:Cyclophosphamide / Q000008:administration & dosage / Q000627:therapeutic use*; D005354:Fibrosarcoma / Q000188:drug therapy* / Q000276:immunology / Q000532:radiotherapy; D007165:Immunosuppression Therapy; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D009368:Neoplasm Transplantation; D009374:Neoplasms, Experimental / Q000188:drug therapy / Q000276:immunology / Q000532:radiotherapy; D013997:Time Factors
D003520:Cyclophosphamide