Role of Interferon in the Anti-Melanoma Effects of Poly (I).Poly (C) and Newcastle Disease Virus

Abstract

WE have shown that intraperitoneal injection of the synthetic RNA, poly (I).poly (C), markedly inhibits the growth of B16 malignant melanomas and prolongs the lives of the C57 mice bearing them^1–3. The mechanism of this action is not known. We and others have shown that this inhibition does not seem to involve the murine immune system^4–6. We have been unable to demonstrate inhibition of B16 melanoma in mice with exogenous murine interferon (ref. 4 and R. S. B., A. W. K., and J. T. V., unpublished), although such inhibition has been shown with other murine malignancies⁷; however, we used lower doses of interferon. We have been able to demonstrate consistently direct inhibitory effect of poly (I).poly (C) on B16 melanoma cells in culture only at concentrations of 200 µg or greater per ml (R. S. B., A. W. K., Hamburg, S., and Wininger, J., unpublished), levels almost certainly far in excess of those reached in vivo.