Treatment of transplanted rat tumours with double-stranded RNA (BRL 5907). I. Influenced of systemic and local administration.

Growth of transplanted rat tumours was retarded and in some cases completely suppressed when cells were injected subcutaneously in admixture with double stranded RNA (ds-RNA). This response required intimate contact between ds-RNA and tumour cells and systemic treatment with the agent failed to prevent progressive growth of a range of rat tumours. Direct cytotoxic effects of ds-RNA may contribute to tumour suppression since the compound was cytotoxic in vitro for cultured tumour cells. The involvement of host factors is suggested, however, by the in vivo tests showing variations in susceptibility to ds-RNA mediated tumour suppression similar to that previously observed with bacterial adjuvants.